Category: Class 7

Std 7 Science Chapter 18 Sound: Production of Sound Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 18 Sound: Production of Sound Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 18 Sound: Production of Sound Question Answer Maharashtra Board

1. Fill in the blanks:

Question a.
Sound is generated by the rhythmic ……………. of any object.
Answer:
vibrations

Question b.
The frequency of sound is measured in …………….. .
Answer:
Hertz (Hz)

Question c.
If …………….. of sound is decreased its loudness also decreases.
Answer:
intensity

Question d.
A medium is necessary for …………… of sound.
Answer:
generation

2. Match the pairs.

Question a.

Answer:

3. Give scientific reasons.

Question a.
In earlier times, people used to listen for the arrival of a distant train by putting their ear to the rails.
Answer:

1. It was a technique that worked better in those days when train speed were slower than they are today and when there were more rail joints.
2. When people would put their ear to the rail they could hear vibration caused by the wheels moving over the joints. ,
3. Metal being a solid is an efficient medium for the sound to travel and so the sound can propagate further in the rail than would in air as speed of sound is faster in solids than in air.

Question b.
The sounds generated by a tabla and sitar are different.
Answer:

1. In tabla where leather is fitted, sound gets generated when the leather surface is thumped by fingers or palm.
2. The waves thus created travel in two dimensions. Sitar is having strings attached to pumkin box called sound box.
3. Sounds generated by tabla and a sitar are different because they have different pitch and frequencies.

Question c.
If you were both on the moon your friend will not be able to hear you call.
Answer: Yes, your friend will not be able to hear your call because sound needs a medium for transmission since it is a mechanical wave it cannot travel through vaccum.

1. As there is no air on the moon and sound is actually vibration in air.
2. So astronauts communicate to each other by signals or microphones in space even when they are closer.

Question d.
We can hear the movement of a mosquito wings but we cannot hear the movement of our hands.
Answer:

1. Humans cannot hear frequency less than 20 Hz. In the movement of hands oscillations does take place but is less than frequency that humans can hear.
2. Mosquitos wings flap in air.
3. When they fly in air it produces buzzing sound in our ears.
4. The movement of mosquito wings produces sound greater than 20 Hz.
5. Sound is the reception of such waves and their perception by the brain.

4. Write answers to the following questions.

Question a.
How is sound produced?
Answer:

1. Sound is generated due to the vibration of an object, e.g. bell, string or diaphragm of a musical instrument.
2. Vibrations are imparted to the molecules in the air. These vibrations reach our ears through the air and sound is heard.
3. Vibrations of an object is necessary for generation of sound.
4. These vibrations in air are called travelling longitudinal waves which we can hear.

Question b.
What does the intensity of sound depend upon?
Answer:

1. The intensity of sound is proportional to the square of the amplitude of vibration, e.g. If the amplitude is doubled the intensity of sound becomes four times.
2. Therefore the loudness or softness of sound is dependent on the intensity of sound and sound level.

Question c.
Explain how the frequency of oscillation is related to the length of a pendulum and the amplitude of its oscillation.
Answer:

1. Given an oscillatory motion to the pendulum, the maximum distance between the original position A of the pendulum and extreme position B or C is called the amplitude of oscillation. AB, AC is the amplitude of oscillation.
2. The number of oscillations completed by an oscillator in one second is called the frequency of oscillation.

Relation between frequency and length of a pendulum: If the length of the pendulum increases the period of oscillations also increases.
We know time period of oscillations = \(\frac{1}{\text { Frequency }}\)
If time period increases, frequency decreases, therefore, if the length of the pendulum increases frequency will decrease.
Relation between frequency and amplitude: Frequency of oscillation is independent of its amplitude of oscillation.

Question d.
Explain the two ways by which the pitch of the sound generated by a stretched string can be changed?
Answer:
1. A string vibrates with a particular fundamental frequency. It is however possible to produce pitches with different frequencies from the same string.

2. The two properties of the string that affect its frequency are length and diameter.

3. When the length of a string is changed, it will vibrate with a different frequency. Shorter strings have higher frequency and therefore higher pitch.

4. When a musician presses her finger on a string, she shortens its length. The more fingers she adds to the string, the shorter she makes it, higher will be the pitch.
Diameter: Thick strings with large diameter vibrate slower and have lower frequency than the thin ones.

Project:

Question a.
The bat, a mammal, flies during the night manoeuvering with the help of the ultrasonic sounds it produces. Find out more about this.

Class 7 Science Chapter 18 Sound: Production of Sound Important Questions and Answers

Fill in the blanks:

Question 1.
Bats detect the obstacles in their path by receiving the reflected ………….. .
Answer:
ultrasonic waves

Question 2.
An object that moves back and forth is called ……………. .
Answer:
an oscillator

Question 3.
If the length of a pendulum is increased the time period of oscillation ………………. .
Answer:
increases

Question 4.
The …………… of a wave is the maximum distance moved by the object on either side of the mean position.
Answer:
amplitude

Question 5.
Sound waves do not travel through ……………… .
Answer:
vaccum

Question 6.
The frequency above which sound is not audible to the human ear is …………….. .
Answer:
50,000 Hz

Question 7.
Number of vibrations in a second is called …………….. .
Answer:
frequency

Question 8.
Higher the frequency greater will be the ………….. .
Answer:
Pitch

Question 9.
The loudness of sound depends on ………….. .
Answer:
amplitude

Question 10.
Loudness of sound is measured in units of ………………. .
Answer:
decibel dB

Question 11.
100 hertz is equal to hundred oscillations in ………………. .
Answer:
one second

Name the following:

Question 1.
The sound frequencies above 20,000 Hz.
Answer:
ultrasonic

Question 2.
The medium through which sound is most clearly propagated.
Answer:
solids

Question 3.
The range of frequency in which humans can hear sound.
Answer:
20 – 20,000 Hz

Question 4.
The sound level physically painful to humans.
Answer:
above 100 dB

Question 5.
The technique used by bats to find their way.
Answer:
echolocation

Question 6.
The unit of frequency of sound.
Answer:
Hertz

Question 7.
The unit of sound level or intensity.
Answer:
Decibel

Question 8.
The scientist in whose honour was the unit decibel named for intensity of sound.
Answer:
Alexander graham Bell

Question 9.
Bats and dolphins can hear these sound frequencies.
Answer:
Ultra sonic sound

Question 10.
The sound frequencies used in RADAR systems.
Answer:
Ultra sonic sound

Answer in one or two sentences:

Question 1.
How is sound produced?
Answer:
Sound is produced by vibration of an object.

Question 2.
What produces sound in human beings ?
Answer:
The vibration of the vocal chords in our larynx or voice box produces sound.

Question 3.
What is oscillatory motion?
Answer:
To and fro motion of an object (oscillator) on either side of a central position is called oscillatory motion.

Question 4.
What is periodic motion?
Answer:
The motion of an object repeated again and again at fixed intervals of time is called periodic motion.

Question 5.
What is frequency of oscillation?
Answer:
The number of oscillations completed by an oscillator in one second is called the frequency of oscillation.

Question 6.
How is intensity of sound and amplitude of vibration related?
Answer:
The intensity of sound is proportional to the square of the amplitude of vibration. For example, if the amplitude is doubled the intensity becomes four times as much.

Question 7.
What happens if the frequency of sound is greater than 1000 Hz or 100 dB?
Answer:
If frequency of sound is increased more than 100dB, the hearing can be temporarily affected which can result in temporary deafness.

Question 8.
What is infrasonic sound?
Answer:
A sound with a frequency less than 20Hz is called infrasonic sound.

Question 9.
What is application of ultrasonic sound?
Answer:
Ultrasonic sound is used in ships as a system known as ‘SONAR’ to detect the obstacle beneath the ocean as well as the depth of an ocean.

Question 10.
What is the difference between pitch and frequency?
Answer:
Pitch is directly proportional to the frequency of a sound whereas frequency is the repeating vibrations per unit time.

Question 11.
What happens when the rubber band is stretched with a greater force and released?
Answer:
When a rubber is stretched with a greater force and released, the amplitude increases which in turn result in a louder sound being generated.

Question 12.
What happens to frequency if the amplitude is changed?
Answer:
The frequency remains the same even if the amplitude is increased or decreased.

Define:

1. Echo: It is a repetition of sound due to the reflection of original sound by a large and hard obstacle.
2. Frequency: It is defined as the number of vibrations per unit time.
3. Hertz (Hz): One hertz is one vibration per second.
4. Ultrasonic vibration: Sounds of frequency higher than 20,000 Hz are called the ultrasonic.
5. Time period: The time taken by an object to complete one oscillation is called time period.
6. Amplitude: The distance between the mean or central position to the extreme position of an oscillator on either side is called amplitude.

Say True or False with explanation:

Question 1.
Sound cannot travel in vacuum.
Answer:
True. Sound needs a medium to travel through. Since vacuum does not provide any medium, sound cannot travel through it.

Question 2.
If the amplitude of vibration is large, sound is feeble.
Answer:
False. When the amplitude of vibration of a sound is large, the sound is very loud. The sound is feeble, when the amplitude is small. Loudness of a sound is proportional to the square of the amplitude of its vibration.

Question 3.
For human ears, the audible range is 2 Hz to 20,000 Hz.
Answer:
True. Human being can hear sounds only within the range of 20-20,000 Hz. We cannot hear the sound having frequency out of this range.

Question 4.
The lower the frequency of vibrations the higher is the pitch.
Answer:
False. Pitch of sound increases when the frequency of vibration increases. The pitch of a sound is directly proportional to its frequency.

Question 5.
Unwanted or unpleasant sound is termed as music.
Answer:
False. Unwanted, or unpleasant sounds are termed noise. Sounds which are melodious, and pleasing to ears are called music.

Question 6.
Noise pollution may cause partial hearing impairment.
Answer:
True. Unwanted, unpleasant sounds are called noise. If one is subjected to noise continuously for a long time, one may suffer from partial hearing impairment.

Question 7.
Time taken by an object to complete one oscillation is called time period.
Answer:
True. Time taken by an object to complete one oscillation is called time period.

Solve the following problems:

Question 1.
A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.
Answer:
Frequency is the number of oscillations per second of a vibrating body.

The time taken to complete one oscillation (to and fro) is known, as time period.

Question 2.
The sound from a mosquito, is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration?
Answer:
The time taken to complete one oscillation (to and fro) is know as time period.

Give scientific reasons:

Question 1.
Loud speakers should not be put in congested areas.
Answer:

1. The loudness or softness is indicated by the intensity of sound and sound level.
2. By putting loud speakers in congested areas, the intensity of sound being more than 100 dB will cause ill effects like temporary deafness and a prolonged exposure can lead to permanent damage.

Answer the following:

Question 1.
Why are the ceilings of concert halls curved?
Answer:
The ceilings of concert halls are curved because sound after reflection from the ceiling it reaches all the comers of the hall and is audible to each person in the hall.

Question 2.
Have you ever heard the sound of movement of hands and falling of leaves from a tree?
Answer:

1. The term infrasonic refer to sound waves below the frequencies of audible sound i.e. under 20 Hz.
2. Humans cannot hear infrasonic sound.
3. Movement of hands and falling of leaves comes below this audible range. Therefore we cannot hear these sounds.

Question 3.
How can dogs perceive in advance the signals of an impending earthquake?
Answer:
Dogs can hear sounds upto about 65,000 Hz. That’s why dogs can receive ultrasonic sound signals produced by the vibration of the earth and start barking in advance before the actual earthquake is felt.

Question 4.
State the uses of Ultrasonic sound.
Answer:
Uses of Ultrasonic sound are:

1. To clean delicate ornaments and the tiny parts of a watch.
2. To observe internal organs of the body.
3. To detect tumors in the brain.
4. To detect faults in a metal.
5. In RADAR systems
6. To Kill certain microbes and insects.
7. SONAR (Sound navigation and ranging) is used to locate the seabed or the position of a ship.

Use your brainpower!

Answer the following questions:

Question 1.
Will a sound be generated no matter how the ruler is kept on the table.

Answer:

1. No, If the ruler kept on the table is only a little part off the table, it will not vibrate with a greater force.
2. On the contrary if the ruler is kept with a larger portion off the table it will vibrate with a greater force generating louder sound.

Question 2.
Is there any correlation between the length of the free part of the ruler and the sound generated?
Answer:
Yes, vibrating ruler pushes the molecules in the air producing sound waves. More the length of free part of ruler less will be the vibrations and less will be the frequency and pitch of the sound. If the length of free part of ruler is shorter it vibrates more quickly producing sound of higher frequency and pitch.

Question 3.
If the ruler is plucked while it is held with 25 cm of it off the table, does it makes any sound? If there is no sound, look for the reason why it is so?
Answer:
No, the ruler vibrates very slowly, which has frequency which is not audible.

Question 4.
What would be the difference perceived between hearing only two pupils in the class talking to each other and all the children talking to one another at the same time?
Answer:

1. When two pupils talk to each other, the sounds of two frequencies produced can be heard clearly.
2. When all the children talk to one another sounds of many frequencies produced can not be heard clearly.
3. Sound level will be more creating loud noise.

Maharashtra State Board Class 7 Science Textbook Solutions

• Cell Structure and Micro-organisms Class 7 Science Textbook Solutions
• The Muscular System and Digestive System in Human Beings Class 7 Science Textbook Solutions
• Changes – Physical and Chemical Class 7 Science Textbook Solutions
• Elements, Compounds and Mixtures Class 7 Science Textbook Solutions
• Materials We Use Class 7 Science Textbook Solutions
• Natural Resources Class 7 Science Textbook Solutions
• Effects of Light Class 7 Science Textbook Solutions
• Sound: Production of Sound Class 7 Science Textbook Solutions
• Properties of a Magnetic Field Class 7 Science Textbook Solutions
• In the World of Stars Class 7 Science Textbook Solutions

Std 7 Science Chapter 13 Changes Physical and Chemical Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 13 Changes – Physical and Chemical Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 13 Changes Physical and Chemical Question Answer Maharashtra Board

1. Distinguish between the following.

Question a.
Physical change and Chemical change
Answer:

Question b.
Periodic changes and Non-periodic change
Answer:

Question c.
Natural change and Man-made change
Answer:

2. Under which different types can the following changes be classified?

Question a.
Conversion of milk into yoghurt.
Answer:
Manmade (useful).

Question b.
Bursting of cracker.
Answer:
Manmade (fast change).

Question c.
Occurrence of an earthquake.
Answer:
Non-periodic.

Question d.
Revolution of earth around the sun.
Answer:
Periodic. (Natural change)

Question e.
Stretching of a spring.
Answer:
Physical, reversible change.

3. Give reasons.

Question a.
While purchasing canned food, its expiry date should be checked.
Answer:

1. Canned food is processed food.
2. After certain period of time it may get spoilt due to some growth of micro-organism it may get intoxicated.
3. If we consume such food we may get food poisoning, so we should check the expiry date.

Question b.
An iron article should be given a coat of paint.
Answer:

1. When an iron article is kept for long time it gets corroded due to presence of oxygen in atmosphere.
2. Iron gets oxidized to iron oxide which forms a reddish brown layer on it and iron gets rusted.
3. It is called corrosion. Due to corrosion things become weak.
4. So an iron article should be given a coat of paint so that it is protected against corrosion.
5. Paint gives protection to iron.

Question c.
A Wooden article should be polished.
Answer:

1. When a wooden article comes in contact with moisture there is possibility of fungal growth and also termites will make wooden article brittle and break.
2. So a wooden article should be polished which forms a protective layer.
3. It does not allow the wooden article to get decayed by moisture or attacked by termite.

Question d.
Copper and brass utensils should be tinned.
Answer:

1. Due to corrosion of copper or brass a greenish layer is seen to form on it.
2. So to protect copper and brass utensils from corrosion they are coated with tin.
3. This process is called thinning.

Question e.
A dry handkerchief gets wet at once on dipping in water, but it takes long for a wet handkerchief to dry.
Answer:

1. The dry fibres of handkerchief absorbs water to its maximum capacity immediately that is why handkerchief gets wet at once.
2. When wet handkerchief dries, all the water absorbed has to become water vapour by evaporation.
3. This depends on surrounding air and heat.
4. That is why wet handkerchief takes a long time to dry.

4. What will you take into account while identifying the following:

Question a.
A physical change in a substance.
Answer:
I will take into account the following facts.

1. Whether the shape, size or state of the substance is changed.
2. Whether it is a temporary change.
3. Whether it is a reversible change.

Question b.
A chemical change in a substance.
Answer:
I will take into account the following facts.

1. Whether a new substance is formed.
2. Whether it is a permanent change.
3. Whether it is a non-reversible change.

5. Read the paragraph and note down the various types of changes it mentions.

Question a.
Read the paragraph and note down the various types of changes it mentions.
It was nearing six o’clock in the evening. The sun was setting. A breeze was blowing. Leaves on the tree were shaking. Sahil was sitting in the courtyard, rolling balls of wet soil and shaping them into various toys. Then he felt hungry and went into the house. Mother made a dough from wheat flour and fried purees. While eating hot purees, his attention was drawn outside the window. It had started raining. There was lighting too. Sahil was enjoying his dinner in the dim light.
Answer:

1. Clock showing six o’clock time – It is a periodic change.
2. Sun was setting – A periodic change.
3. Breeze was blowing – A natural change.
4. Leaves shaking – A natural change.
5. Making toys from wet soil – Physical change.
6. Making dough from wheat flour – Physical change
7. Frying purees – Chemical change.
8. Raining – Natural change.
9. Lightning – Natural change.

Project:

Question a.
Visit a place where work like powder coating. spray painting is done. Make a note of the information you obtain.

Class 7 Science Chapter 13 Changes – Physical and Chemical Important Questions and Answers

Fill in the blanks and rewrite the sentences:

Question 1.
Burning of candle is a ………………. change.
Answer:
chemical

Question 2.
Cooking of vegetable is ………………. change.
Answer:
useful

Question 3.
A man painted his main gate made up of iron to prevent it from ………………. .
Answer:
rusting

Question 4.
Galvanization is a process used to prevent the rusting of ………………. .
Answer:
iron

Question 5.
Making sugar solution is a ………………. change.
Answer:
physical

Question 6.
A physical change is generally ………………. .
Answer:
temporary

Question 7.
Grinding of wheat grain changes its size, it is a ………………. .
Answer:
physical change

Question 8.
Iron benches kept in lawns and gardens get rusted. It is a change because a new ………………. is formed.
Answer:
chemical, product.

State whether the following statements are True or False. Correct and rewrite the false statement:

Question 1.
Iron and rust are the same substance.
Answer:
False, Rust is oxide of iron.

Question 2.
Iron pipes coated with zinc do not get rusted easily.
Answer:
True

Question 3.
Formation of manure from leaves is a physical change.
Answer:
False, it is a chemical change.

Question 4.
Cutting a log of wood into pieces is a chemical change.
Answer:
False, it is a physical change.

Question 5.
Digestion of food is a chemical change.
Answer:
True

Question 6.
Melting of wax is a chemical change.
Answer:
False, it is a physical change.

Question 7.
Dissolving sugar in water is physical change.
Answer:
True

Question 8.
Changes in which new substances are formed are called physical changes.
Answer:
False, they are called chemical change.

Question 9.
Breaking down of larger food particles into smaller particles is a chemical change.
Answer:
False, it is a chemical change.

Question 10.
Setting of curd is a physical change.
Answer:
False, it is a chemical change.

Question 11.
Heating of iron is a physical change.
Answer:
True

Question 12.
Cooking a vegetable is chemical change.
Answer:
True

Question 13.
Freezing water into ice is a chemical change.
Answer:
False, it is a physical change

Define the following.

Question 1.
Physical change:
Answer:
In a physical change the material may change shapes or forms but no new compounds are formed and change can generally be reversed by reversing the conditions.

Question 2.
Chemical change
Answer:
A chemical change produces a new substance having new and different properties and which cannot be reversed by reversing the conditions.

Question 3.
Periodic change
Answer:
Some changes occur again and again after . a definite interval of time, such changes are called periodic changes.

Question 4.
Non-periodic change
Answer:
Changes that do not repeat themselves after a fixed interval of time are called non-periodic changes.

Question 5.
Reversible change
Answer:
The changes that can occur in a forward and reverse direction again and again are called reversible changes.

Question 6.
Irreversible change.
Answer:
The changes which we cannot reverse back to same thing are called Irreversible changes e.g. Burning of wood, paper.

Question 7.
Condensation
Answer:
The process by which matter changes from its vapour or gaseous state into its liquid state by cooling is called condensation.

Question 8.
Corrosion of metals
Answer:
When an iron article rusts, a reddish brown layer (of iron oxide) forms on it. A greenish layer is seen to form on a copper article. This is called corrosion of metals.

Question 9.
Galvanization
Answer:
Iron articles are given a thin coat of zinc to prevent corrosion this is called galvanization.

Question 10.
Tinning
Answer:
Copper and brass articles are coated with tin. This is called tinning.

Question 11.
Natural change
Answer:
Changes that occur naturally like ripening of a fruit, spoiling of milk are called natural changes.

Question 12.
Man-made change
Answer:
Man-made changes are result of human- activity. E.g. Burning of fossil fuel.

Question 13.
Useful change
Answer:
Many changes such as baking bread, cooking food are useful to us, they are called useful changes.

Question 14.
Harmful change
Answer:
The changes that are not useful or changes that harms living things or the environment are called harmful changes.

Name or Give two example of:

Question 1.
Two physical changes.
Answer:

1. Melting of wax
2. Melting of ice

Question 2.
Two chemical changes.
Answer:

1. Burning of wax candle
2. Burning of wood or paper.

Question 3.
Two periodic changes.
Answer:

1. Occurrence of day and night
2. change of seasons

Question 4.
Two non-periodic changes.
Answer:

1. A meteor moving across the sky.
2. A bird sitting on a tree flies away.

Question 5.
Two reversible changes.
Answer:

1. Melting of wax.
2. Freezing water into ice.

Question 6.
Two irreversible changes.
Answer:

1. Ripening of a mango.
2. Burning of wood

Question 7.
Two natural changes.
Answer:

1. Lighting in the sky.
2. Earthquake.

Question 8.
Two manmade changes.
Answer:

1. Baking bread
2. Cooking food.

Question 9.
Two useful changes.
Answer:

1. Ripening of mango
2. Curdling of milk.

Question 10.
Two harmful changes.
Answer:

1. Spoiling of milk.
2. Air pollution.

Match the following:

Question 1.

Answer:

Question 2.

Answer:

Distinguish between the following.

Question 1.
Reversible change and Irreversible change
Answer:

Under which different types can be following changes be classified:

Question 1.
Formation of curd from milk.
Answer:
Manmade change (useful), chemical

Question 2.
Burning of wood or paper.
Answer:
Manmade, chemical change.

Question 3.
Glowing of bulb.
Answer:
Manmade (fast).

Question 4.
Rusting of iron.
Answer:
Chemical change (harmful)

Question 5.
Burning of Camphor.
Answer:
Chemical change

Question 6.
Souring of milk.
Answer:
chemical change (harmful)

Question 7.
Digestion of food.
Answer:
Chemical change (useful), irreversible

Question 8.
Change of season.
Answer:
Periodic change, natural change

Question 9.
Day and night formation.
Answer:
Periodic change

Question 10.
Heartbeat.
Answer:
Periodic change

Question 11.
Water pollution.
Answer:
Manmade, harmful change

Question 12.
Air pollution.
Answer:
Manmade, harmful change

Question 13.
Burning of fossil fuel
Answer:
Manmade (irreversible change)

Question 14.
Ripening of fruit.
Answer:
Natural, chemical

Question 15.
Change-in climate.
Answer:
Natural, periodic

Question 16.
Melting of ice into water
Answer:
Physical change

Question 17.
Germination of seed.
Answer:
Natural, slow, desirable.

Question 18.
Bursting of balloon.
Answer:
Irreversible change (fast).

Give reasons:

Question 1.
The burning of wax is a chemical change
Answer:

1. Because when the cotton wick embedded in the candle is burnt, ash and smoke is formed.
2. It is not possible to make wick again from the smoke and ash.

Can you tell?

Answer the following questions:

Question 1.
We see many man-made materials in our day-to-day life. For what purpose are they produced.
Answer:
We see many man-made matrical in our day to day life. For example,

1. Air conditioners for getting cool air in houses offices and cars.
2. Wooden furniture made from wood obtained by cutting trees.
3. Refrigerators to protect food from spoiling.

Question 2.
You made a link from the glass piece. How will you change the shape of the link to give it its original shape?
Answer:
Heat the glass piece again at the link. When it becomes soft break it.

Question 3.
How will you restore the original candle after melting one ?
Answer:
Collect the melted wax and give the required shape when it is soft.

Question 4.
What comes after daytime?
Answer:
Night time (periodic change)

Question 5.
What is the next stage after sunrise?
Answer:
Sunset (periodic change)

Question 6.
What comes after a high tide in the sea?
Answer:
Low tide (periodic)

Question 7.
A bird sitting on a tree flies away.
Answer:
non-periodic change.

Question 8.
A meteor streaking across the sky.
Answer:
non-periodic change.

Use your brainpower!

Answer the following questions:

Question 1.
What kind of change is the falling of a tree in a storm?
Answer:
Natural change.

Question 2.
What kind of a change is the conversion of milk into yoghurt?
Answer:
Manmade ‘ change, useful change and a chemical change

Question 3.
What is meant by irreversible change? Give some examples.
Answer:

1. An irreversible change is a permanent change that cannot be undone, cannot reverse it back to original substance.
2. In irreversible change new materials are always formed.
3. Irreversible changes are permanent changes.
4. Heating, burning, mixing, powdering are few processes which causes irreversible changes.

Examples:

• burning of paper or wood
• cooking of raw egg.

Question 4.
Which type of change is the change of seasons from summer to rains to winter?
Answer:
Natural and periodic change

Question 5.
Which hands of a clock show periodic changes from 6.00 am to 6.00 pm? How many times?
Answer:
Small (hour) hand (12 times).

Question 6.
Which of the following are physical changes and which are chemical changes?
(making a table from wood, burning wood, breaking of a glass object, ripening of a tomato, rusting of iron.
Answer:

Question 7.
What are periodic and non-periodic changes?
Answer:
1. We find that some changes occur again and again after a definite interval of time. Such changes are called Periodic changes, e.g. Sunrise and Sunset.
2. On the other hand, it cannot be ‘Slid for sure when certain changes will recur after one occurrence. Even if they recur, the time interval is not fixed. Such changes are called non-periodic changes, e.g. A meteor streaking across the sky.

Question 8.a.
Which changes shown in the pictures below are temporary.

Answer:
(b) Removing iron nails with help of magnet
(d) Conversion of ice cubes into water.

Question b.
Which of the changes are permanent?
Answer:
Bud blooming into flower.

Question c.
In which did the original matter undergo a change?
Answer:

1. In permanent change
2. Bud blooming into flower.

Question d.
In which the original matter remain unchanged?
Answer:
In temporary changes
(b) iron nails
(d) ice cubes.

Question e.
In which of the changes was a new substance with a new property formed?
Answer:

1. Bud blooming into flower.
2. Ice to water, Ice is in solid state, Water is in liquid state.

Question 9.
Give some examples of fast and slow changes that occur in your surroundings.
Answer:

Maharashtra State Board Class 7 Science Textbook Solutions

• Cell Structure and Micro-organisms Class 7 Science Textbook Solutions
• The Muscular System and Digestive System in Human Beings Class 7 Science Textbook Solutions
• Changes – Physical and Chemical Class 7 Science Textbook Solutions
• Elements, Compounds and Mixtures Class 7 Science Textbook Solutions
• Materials We Use Class 7 Science Textbook Solutions
• Natural Resources Class 7 Science Textbook Solutions
• Effects of Light Class 7 Science Textbook Solutions
• Sound: Production of Sound Class 7 Science Textbook Solutions
• Properties of a Magnetic Field Class 7 Science Textbook Solutions
• In the World of Stars Class 7 Science Textbook Solutions

Std 7 Science Chapter 17 Effects of Light Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 17 Effects of Light Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 17 Effects of Light Question Answer Maharashtra Board

1. Fill in the blanks.

Question a.
When the beams from the headlights of a car fall on an object in the night, the shadows – called ………. and ………… . can be seen.
Answer:
umbra, penumbra

Question b.
During a lunar eclipse the shadow of the …………. falls on the ………. .
Answer:
earth, moon

Question c.
During a solar eclipse the shadow of the ………. falls on the ………… .
Answer:
moon, earth

Question d.
Various shades of colour are seen in the sky at sunrise and sunset due to ……….. .
Answer:
scattering of light

2. Give reasons.

Question a.
Space beyond the earth’s atmosphere appears dark.
Answer:

1. Space beyond the earth’s atmosphere does have some gas and cosmic dust but there is not any atmosphere.
2. As there are no particles to scatter the sunlight, the space appears black.

Question b.
We are able to read while sitting in the shade.
Answer:

1. We are able to read because the sun light which falls on the book is scattered and reaches our eyes.
2. While sitting in the shade our eyes adjust to the environment and to amount of light available. That is how we are able to read.

Question c.
We should not observe the solar eclipse with naked eyes.
Answer:

1. During a solar eclipse ultra-violet rays which are harmful to us reach the earth and may lead to eclipse blindness or retinal bums and cataracts.
2. In order to protect our eyes a solar eclipse should never be watched with the naked eye.
3. A special type of goggles should be used for this.

3. Give some examples of scattering of light that we come across in day to day life.

Question a.
Give some examples of scattering of light that we come across in day to day life.
Answer:

1. The formation of rainbow, shift in position of stars, increased day time, mirage, inverted image, glittering of diamond, the working of lens and prism, bending of pen in water are examples of scattering of light.
2. The blue colour of the sky is due to the scattering of sunlight by the molecules of air.
3. During sunrise and sunset, sunlight has to travel greater distance, so shorter wavelength gets scattered off and removed and only orange and red with longer wavelengths reach us.
4. So during sunrise and sunset, sky appears fed and orange.

4. Why is the shadow of a bird flying high not seen on the earth?

Question a.
Why is the shadow of a bird flying high not seen on the earth?
Answer:

1. Birds flying high in the sky do cast their shadow but because they are shading an area that is very tiny the shadow is not visible.
2. The higher the bird flies, the smaller the shadow it casts.
3. Also when the bird flies high, the dark part of the shadow that is called Umbra does not reach the ground so we do not see its shadow.

5. Why is a penumbra not obtained from a point source?

Question a.
Why is a penumbra not obtained from a point source?
Answer:

1. The umbra, penumbra are the distinct parts of a shadow, created by any light source after striking on an opaque object.
2. For a point source, only the umbra is cast sharp dark shadow and not penumbra, because all the light of the point source will be blocked by any shadowing object.
3. Whereas penumbra forms only when some of the light from the source gets blocked by the shadowing object and not all of it does.

6. Answer the following questions in your own words.

Question a.
What is meant by scattering of light?
Answer:

1. Scattering of light is the deviation of light rays from its straight path.
2. As light propagates through the atmosphere, it travels in a straight path until it is obstructed by bits of dust or gas molecules in the atmosphere
3. The process in which light gets deflected by the particles in the medium through which the light passes is called scattering, e.g. The blue colour of the sky is due to the scattering of sunlight by the molecules of air.

Question b.
Does the shadow really vanish in the zero shadow condition?
Answer:
1. Yes, the day on which the sun reaches exactly overhead, at noon, shadow completely disappears.
‘This event can be seen in the region between the Tropic of Cancer (23.5°N) and Tropic of Capricorn (23.5°S).
2. The shadow diminishes and eventually disappears for a while only to reappear later.

Question c.
Will the laser beam be seen if it passes through a glass box which contains a lighted incense stick?
Answer:
Yes, it will be seen.

7. Discuss and write:

Question a.
Write a science based paragraph on ‘What if the sun did not rise’?
Answer:

1. The sun is a star and the centre of our solar system. Everything in our solar system revolves around the sun.
2. If the sun were to suddenly disappear, Earth and the other planets would retain their forward motion, effectively flying off into outer space in a straight line.
3. If the Sun didn’t rise means the Earth’s rotation had come to a screeching halt.
4. Sunrise and sunset are a result of the earth’s rotation so we will not get to see sunrise or sunset. Earth’s spinning generates the magnetic field at the core and it is saving us from harmful rays from the sun.
5. Without sun it would be very dark. No sun means no plants and no animals. Of course, without sun none of us would even exist.
6. Moon will disappear, because the moon dose not produce light. We only see the moon because sunlight is reflected by the moon.
7. Without the sun’s warmth, Earth would quickly become a much colder place. Life would be difficult, oceans will freeze.
8. Without sun rays, all photosynthesis on earth would stop. All plants would die.
9. All animals that rely on plants for food, including humans would die.

Question b.
What efforts will you make to remove the misconceptions about eclipses?
Answer:
Solar, lunar eclipse have been traditionally observed as an ominous sign and therefore superstitions are prevalent in association with these natural phenomena.
1. All these misconceptions should be removed by explaining scientifically the process of eclipse how it happens: (a) Explain with the help of diagram and models of sun, moon and earth, (b) Explain how special glasses which will protect us from UV rays, and excess heat can be used to observe eclipses safely.
2. Also inform that eclipses are natural phenomena and can be predicted in advance.

Question c.
Various eclipses and the conditions during that period.
Answer:
There are two eclipses:

1. Solar eclipse
2. Lunar eclipse

1. Solar eclipse:
There are two types of Solar eclipse, (a) Total solar eclipse (b) Partial solar eclipse

a. Total solar eclipse: In total solar eclipse, the moon is between the sun and the earth and the moon shadow covers the sun disc fully by perfect alignment. The part of the earth that lies in the umbra of the moon experiences total solar eclipse.

b. Partial solar eclipse: In partial solar eclipse, the moon is between the sun and the earth arid the moon shadow does not cover the sun disc fully, because of imperfect alignment. The part of the earth that lies in the penumbra of the moon experiences partial solar eclipse.

c. The solar eclipse occur on a new moon day.
d. Solar eclipse last for few minutes.

2. Lunar eclipse:
There are two types of Lunar eclipse, (a) Total lunar eclipse (b) Partial lunar eclipse

a. Total lunar eclipse: In total lunar eclipse, the earth comes in between the sun and the moon and the earth’s shadow covers the moon’s surface fully because of perfect alignment.

b. Partial lunar eclipse: In partial lunar eclipse, the earth’s shadow does not cover the moon’s surface fully because of inperfect alignment. A small part of the moon’s surface is covered by umbra part of earth’s shadow.

c. The lunar eclipse occurs on a full moon night.
d. Lunar eclipse last for few hours.

8. Explain the difference:

Question a.
Point sources and Extended sources.
Answer:

Question b.
Umbra and Penumbra.
Answer:

Project:

Question a.
Obtain information about the special goggles used to watch a solar eclipse.

Class 7 Science Chapter 17 Effects of Light Important Questions and Answers

Fill in the blanks.

Question 1.
During solar eclipse ………….. comes between the sun and earth.
Answer:
moon

Question 2.
A solar eclipse is seen only on a ………….. day.
Answer:
new moon day

Question 3.
During lunar eclipse ……………. comes between the sun and the moon.
Answer:
earth

Question 4.
A lunar eclipse is seen only on a ………….. night.
Answer:
full moon

Question 5.
The day on which the sun reaches exactly overhead is called the …………… .
Answer:
zero shadow day

Question 6.
As seen from the earth, when a planet or star passes behind the moon, that state is called a ………….. .
Answer:
occultation

Give scientific reasons:

Question 1.
Sky appears blue to us.
Answer:

1. Sunlight is scattered by the molecules of gases like nitrogen, oxygen in the atmosphere.
2. The blue colour in the sunlight which is at shorter wavelength is scattered the most than other colours and therefore the sky appears blue.

Question 2.
Solar eclipse is either partial or total.
Answer:

1. When the moon comes in between the sun and the earth and the solar disc is corripletely covered by the moon, it is called total solar eclipse.
2. When the solar disc is not covered fully by the moon, it is partial solar eclipse.

Explain the difference:

Question 1.
Solar eclipse and Lunar eclipse.
Answer:

Solar eclipse	Lunar eclipse
1. When the moon comes between the sun and the earth, a shadow of the moon is cast on the earth and sun cannot be seen from the part in shadow. This is called a solar eclipse.	1. When the earth comes between the sun and the moon a shadow of the earth is cast on the moon and a part of the moon in covered this is called the lunar eclipse.
2. A solar eclipse is seen only on a new moon day.	2. A lunar eclipse is seen only on a full moon night.
3. A solar eclipse should never be watched with the naked eye. because ultra violate rays which are harmful to us reach the earth	3. A lunar eclipse can be seen with the naked eye.
4. It can be seen for a few minutes only.	4. It can be seen over a period of a few hours.

Explain diagrams:

Question 1.
Explain Solar eclipse with diagram.
Answer:
Solar eclipse:

1. During its revolution, when the moon comes between the sun and the earth, a shadow of the moon is cast on the earth and the sun cannot be seen from the part in the shadow. This is called a solar eclipse
2. A solar eclipse is seen only on a new moon day.
3. The solar eclipse may be either partial or total,
4. Sometimes the solar disc is completely covered by the moon. This is the total solar eclipse.
5. When the solar disc is not covered fully by the moon, we have a partial solar eclipse.
6. During a solar eclipse, ultra-violet rays which are harmful to us reach the earth.
7. A solar eclipse should never be watched with the naked eye.
8. A special type of goggles should be used for this purpose.
9. Solar eclipse can be seen for a few minutes only.

Question 2.
Explain Lunar eclipse with diagram
Answer:
Lunar eclipse:

1. When the earth comes between the sun and the moon a shadow of the earth is cast on the moon and a part of the moon is covered. This is called the lunar eclipse.
2. A lunar eclipse is seen only on a full moon night. If the whole moon comes in the shadow of the earth, it is a total lunar eclipse.
3. When the shadow of the earth is cast only on a part of the moon, it is a partial lunar eclipse. You can watch a lunar eclipse with the naked eye.
4. A lunar eclipse can be seen over a period of a few hours.

Question 3.
Write a short note on Zero Shadow Day.
Answer:

1. The day on which the sun reaches exactly overhead is called zero shadow day.
2. On this day, at noon, shadow completely disappears.
3. This event can be seen in the region between the Tropic of Cancer (23.5°N) and at tropic of Capricon (23.5°S).
4. The shadow diminishes and eventually disappears for a while only to reappear later
5. This phenomenon occurs twice every year Mumbai got to witness it on May 14, 2018 last year.

Question 4.
Explain the phenomenon of scattering of light with the help of an experiment.
Answer:

1. When the sun rises our surroundings appear illuminated. The entire sky appears bright.
2. This happens because of the dust and other tiny particles in the air. This is the scattering of sunlight by the tiny particles of the various constituents of air.
3. Had there been no atmosphere, the sky would have appeared dark during the day and of course, the sun would be directly seen.
4. This has been verified by observations from the rockets and satellites which go out of the earth’s atmosphere.

Apparatus: A table lamp with a 60 or 100 W milky bulb (LED will not do), thick black paper, sticking tape, a packing needle, 100/200 ml. glass beaker, milk or milk powder, dropper, spoon, etc.

Procedure: Cover the mouth of the lampshade properly with black paper, using sticking tape. Prick a hole of 1 to 2mm diameter in the center of the paper with the help of the packing needle.

1. Take clear water in the beaker. Light the bulb and place the beaker in contact with the hole.
2. Observe from the front and at an angle of 90°.
3. Now add 2-3 drops of milk to the water and stir. Observe again.
4. A few more drops of milk may have to be added to make the water turbid.
5. A blue tinge is seen when observed along the 90° angle. This is the scattered blue light.
6. Because the blue light is scattered, a red-yellow light is seen from the front, and the hole appears reddish.

Question 5.
Short note on Shadow.
Answer:

1. Shadow is a dark patch formed behind an opaque object when it is placed in the path of light.
2. A shadow is formed only when a light source, an opaque object and a screen are present, e.g. during a lunar eclipse we see a part of the earth’s shadow on the surface of the moon.
3. This happens when the earth, the sun, and the moon are in a straight line with the earth between sun and the moon.
4. Here the sun acts as the light source, the earth as the opaque object and moon as the screen.
5. Shadows are formed due the rectilinear propagation of light.
6. The size and the shape of the shadow depend on the position and orientation of the opaque object between the source of light and the screen.
7. If the distance of the object from the source is decreased, then the size of the shadow increases.
8. If the object is moved away from the source, then the size of the shadow decreases.
9. In older days shadows caused by objects placed in the sun were used to measure time. Such a device is called sun dial.

Use your brain power!

Answer the following questions:

Question 1.
Eclipses and transits which will occur recently.
Answer:

• January 6, 2019 – Partial solar eclipse
• January 21, 2019 – Total Lunar eclipse
• July 2, 2019 – Total solar eclipse
• July 16, 2019 – Partial Lunar eclipse
• December 26, 2019 – Annular solar eclipse.

Find Out:

Answer the following questions:

Question 1.
If a few drops of milk are added in the experiment given the reddish colour seen from the front becomes an intense red. However, if many more drops are added the reddish colour is not seen. Why is this so?
Answer:

1. As more and more milk is added, more particles of protein and fat scatter the light and the blue colour is scattered more and more than orange and red light and the beam appears blue from the sides.
2. If few drops of milk are added, along with blue colour, orange and yellow also are scattered and only the intense red is seen from the front.
3. But when many more drops are added, even the red colour is scattered and we do not see any colour from the front.

Question 2.
What is Occultation?
Answer:
As seen from the earth, when a planet or a star passes behind the moon, that state is called an Occultation.

Complete the Chart.

Question 1.

Answer:

• A – Solar B – Lunar
• C – Total Solar
• D – Partial Solar
• E – Total Lunar
• F – Partial Lunar
• G – Moon is not in a straight line between earth and sun
• H – It is in the penumbra region of the moon
• I – The earth comes in between the sun and moon and they are not in a straight line.

Maharashtra State Board Class 7 Science Textbook Solutions

• Cell Structure and Micro-organisms Class 7 Science Textbook Solutions
• The Muscular System and Digestive System in Human Beings Class 7 Science Textbook Solutions
• Changes – Physical and Chemical Class 7 Science Textbook Solutions
• Elements, Compounds and Mixtures Class 7 Science Textbook Solutions
• Materials We Use Class 7 Science Textbook Solutions
• Natural Resources Class 7 Science Textbook Solutions
• Effects of Light Class 7 Science Textbook Solutions
• Sound: Production of Sound Class 7 Science Textbook Solutions
• Properties of a Magnetic Field Class 7 Science Textbook Solutions
• In the World of Stars Class 7 Science Textbook Solutions

Std 7 Science Chapter 8 Static Electricity Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 8 Static Electricity Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 8 Static Electricity Question Answer Maharashtra Board

1. Choose the correct option and fill in the blanks.
(always repulsion, always attraction, displacement of negative charge, displacement of positive charge, atom, molecule, steel, copper, plastic, inflated balloon, charged object, gold)

Question a.
There is ………….. between like charges.
Answer:
always repulsion

Question b.
…………. is responsible for generation of electric charge in an object.
Answer:
displacement of negative charge

Question c.
A lightning conductor is made of a ……………… strip.
Answer:
copper

Question d.
……………… does not get electrically charged easily by rubbing.
Answer:
Steel

Question e.
There is …………………. when opposite electric charges come near each other.
Answer:
always attraction

Question f.
A ……………… canbe detected with an electroscope.
Answer:
charged object

2. Explain why it is not safe to go out with an umbrella when there is heavy raine lightning or thunder.

Question a.
Explain why it is not safe to go out with an umbrella when there is heavy raine lightning or thunder.
Answer:
Large amount of charges get built up in the clouds in rainy and stormy weather.

1. Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
2. Wire of umbrella is made up of metal and cloth is made up of synthetic material.
3. If lightning strikes, then umbrella catches it and there are chances of fire and it would be dangerous.
4. So it is not safe to go out with an umbrella when there is heavy rain.

3. Answer in your own words.

Question a.
How will you protect yourself from lightning?
Answer:

1. To protect from the lightning, we have to put lightning conductor on high rise buildings,
2. we should not stand under a tree in rainy and stormy weather.
3. We should not go out with an umbrella in heavy rain, lightning or thunder.

Question b.
How are charges generated?
Answer:

1. Friction causes a charge to develop, because on rubbing, some negative particles are transferred from one substance to the other and the later develops a negative charge.
2. The substance from which particles are removed lose negative charge and hence, it develops a positive charge.

Question c.
In the lightning conductor, what provision is made for spreading the electricity into the ground?
Answer:

1. The lightning conductor, consists of a long i copper strip with one end forked. This end is ‘ at the highest part of the building.
2. The other end of the strip is connected to a plate of cast iron.
3. A pit is dug in the ground, coal and salt are filled into the pit and the iron plate is placed upright in the pit.
4. There is also a provision for pouring water into it.
5. This helps to spread the electric charge quickly into the ground.

Question d.
Why do farmers stick an iron staff into the ground while working in the field in rainy conditions?
Answer:

1. Large amount of charges get built up in the clouds in rainy and stormy weather.
2. Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
3. Due to iron staff, the charges will be conducted to the earth through iron metal and spread quickly into the ground.
4. This way farmers are saved from lighting strike.

Question e.
Why is lightning not seen every day during the rainy season?
Answer:

1. When air and clouds rub against each other in the sky the upper part of some clouds becomes positively charged and the lower side become negatively charged.
2. When this negative charge at the bottom of the cloud becomes much larger than the charge on the ground, it starts flowing towards the ground in stages, but this doesn’t happen every day. So lightning is not seen every day during the rainy season.

4. What are the characteristics of a static electric charge?

Question a.
What are the characteristics of a static electric charge?
Answer:
Following are the characteristics of a static electric charge.

1. The electric charge generated by friction is called frictional electricity. This charge is produced only at the place of friction, hence it is called static electricity.
2. It remains on the object for a short duration.
3. The charges of static electricity are absorbed in moist air.
4. An electrically charged object attracts another object which has no electric charge.
5. Like charges repel each other.
6. Unlike charges attract each other.
7. Repulsion is the sure test of the existence of a static charge.

5. What is the damage caused by lightning? How will you ereate awareness to prevent it?

Question a.
What is the damage caused by lightning? How will you ereate awareness to prevent it?
Answer:
Due to lightning great damage can occur.

1. It may cause fire.
2. Person on whom lightning strikes may die also.
3. It causes more temperature than sun.

Awareness to prevent it:

1. Guide the people to install lightning conductor on tall buildings.
2. Do not stand on open ground, below a tree, or on a high location during the thunder storms.
3. Do not use plugged in electrical appliances.
4. Do not stand near an electric pole, telephone pole or a tower.
5. Stay in pucca house made of brick and cement.
6. Stand on only wood, a plastic sheet or sack of jute.

Project:

Question a.
Make an electroscope yourself by using a thin aluminium foil and check which substances become electrically charged.

Class 7 Science Chapter 8 Static Electricity Important Questions and Answers

1. Choose the correct option and fill in the blanks.
(always repulsion, always attraction, displacement of negative charge, displacement of positive charge, atom, molecule, steel, copper, plastic, inflated balloon, charged object, gold)

Question 1.
named the electric charges as positive charge and negative charge.
Answer:
Benjamin Franklin

Question 2.
Each atom contains a stationary charge and moving charges.
Answer:
positive, negative

Question 3.
Each atom is electrically
Answer:
neutral

Question 4.
Amber is called in the Greek language.
Answer:
electron

Question 5.
The charges of electricity are absorbed in moist air.
Answer:
static

Question 6.
Electrically charged objects uncharged objects.
Answer:
attract

Question 7.
is used as a test for identifying an electrically charged object.
Answer:
Repulsion

Question 8.
The property of amber to attract things was named electricity by in 1646 AD.
Answer:
Thomas Brown

Question 9.
The electric charge generated by stays only as long as the charged object is near to it.
Answer:
induction

Question 10.
A simple device is used to detect the electric charge on an object.
Answer:
gold leaf electroscope

Question 11.
Lightning is a form of
Answer:
electric charge

Question 12.
The gas protects us from the harmful ultra violet rays coming from the sun.
Answer:
ozone

Question 13.
The is a device used for protection from a lightning strike.
Answer:
lightning conductor

Question 14.
Due to the energy of the lightning, the oxygen in the air is converted into
Answer:
ozone

2. Match the columns:

Question a.

Answer:

Say whether true or false, correct and rewrite the false statement:

Question 1.
Charges cannot be transferred from one body to another.
Answer:
False. Charges can be transferred from one body to another

Question 2.
The word ‘electricity.’ came from the word ‘Elektron’.
Answer:
True

Question 3.
When an inflated balloon is rubbed on silk, it develops a charge.
Answer:
True

Question 4.
An ebonite rod rubbed on woollen cloth develops a positive charge.
Answer:
False. An ebonite rod rubbed on woollen cloth develops a negative charge

Question 5.
A glass rod rubbed on woollen cloth develops a negative charge.
Answer:
False. A glass rod rubbed on woollen cloth develops a positive charge

Question 6.
If the leaves of the electroscope spread only a little, the charge on them is less.
Answer:
True

Question 7.
An atom may have either a positive or a negative charge.
Answer:
False. An atom does not have any charge

Question 8.
When two substances are rubbed on each other, like charges are developed on each.
Answer:
False. When two substances are rubbed on each other unlike charges are developed on each

Question 9.
High rise buildings have lightning conductors.
Answer:
True

Question 10.
It is dangerous to stand under a tree in rainy and stormy weather.
Answer:
True

Give scientific reasons:

Question 1.
Ordinarily, an atom does not have any charge.
Answer:

1. Every atom contains smaller particles with either positive or negative charge.
2. As the number of positively and negatively charged particles in an atom is equal, they neutralize each other.
3. As a result the atom has no charge.

Question 2.
Charge cannot be developed on a copper rod.
Answer:
Charge cannot be developed on a copper rod because only certain pairs of substances give rise to electric charge, on rubbing.

Question 3.
High rise buildings have lightning conductors.
Answer:

1. High rise buildings are prone to lightning strikes during the monsoon.
2. When lightning strikes, a tremendous electric charge is transferred to the earth, which may damage the tall buildings.
3. To prevent this, high rise buildings have a forked metal rod, called a lightning conductor fitted on the top of the building.
4. The lower end of this rod is buried inside the earth.
5. If lightening strikes, the electric charge passes through this conductor and goes in to the earth. In this way the building is saved from damage.

Question 4.
It is dangerous to stand under a tree in rainy and stormy weather.
Answer:

1. Large amount of charges get built up in the clouds in rainy and storming weather.
2. Sometimes these charges are transferred to the earth in the form of a bolt of lightning.
3. Generally lightning strikes tall buildings and trees. If lightning strikes a tree then either the tree may fall or it may catch fire.
4. In both cases this would be dangerous for anyone standing under the tree, hence it is dangerous to stand under a tree in rainy and stormy weather.

Question 5.
Repulsion is a test used for identifying an electrically charged object.
Answer:

1. When a charged object is brought near a neutral object, it gets attracted when two oppositely charged objects are brought close, they get attracted. Therefore, attraction is not a test.
2. But when two like charges are brought close only then repulsion takes place.
3. Therefore, repulsion is the sure test for identifying an electrically charged object.

Question 6.
Mustard seeds when shaken vigorously in a glass bottle stick to the sides of the bottle.
Answer:
When seeds are shaken they get electrically charged and therefore they stick to the neutral walls of the glass.

Answer the following:

Question 1.
Why is the charge developed due to friction called static electric charge?
Answer:
The charge developed due to friction is called 1 static electric charge because the charge remains still on the object.

Question 2.
Why does the charge developed by induction disappear quickly?
Answer:
The charge developed by induction disappears quickly because it is very weak.

Question 3.
Why do the leaves of a gold leaf electroscope fly apart when a charged body touches its disc?
Answer:
The leaves of a gold leaf electroscope fly apart when a charged body touches its disc because like charges develop on both the leaves and hence they repel each other.

Draw a neat labelled diagram of Gold leaf electroscope and describe it.

Answer:

1. This is a simple device to detect the electric charge on object.
2. It consists of a copper rod which has a metal disc at the upper end and two thin gold leaves at the other.
3. The rod is placed in a bottle so that the disc is above the bottle.
4. When an uncharged object is taken near the disc, the leaves remain closed.
5. When a charged object is taken near the disc, both the leaves are charged by the same electric charge, and repel each other.
6. When we touch the disc with our hand, the leaves collapse because the charge in the leaves goes into the earth through our body, and the leaves get discharged.

Use your brainpower:

Question 1.
Do all the objects get charged by rubbing?
Answer:
No. Only certain pairs of substances get charged on rubbing.

Question 2.
Why does a charged balloon stick to a wall?
Answer:
A charged balloon stick to a wall because there is always attraction between a charged object and an uncharged object.

Question 3.
Can we use leaves of some other metal instead of gold, in the electroscope? Which properties must that metal have?
Answer:
We can use other metals than gold in gold leaf electroscope.

1. Only thing is that metal should be malleable and good conductor of electricity.
2. But the best is gold only because we can make extremely thin leaves of gold so even very small charge also can be detected.

Question 4.
What kind of damage is caused by a lightning strike?
Answer:
Due to lightning strike, great damage can occur. It may cause forest fire and burn down things. Person on whom lightning strikes may die. It causes more temperature than sun.

Question 5.
What measures will you take to prevent the damage caused by lightning?
Answer:
Following measures can be taken to prevent the damage caused by lightning:

1. Always put lightning conductor on tall buildings.
2. Do not stand on open ground, below a tree or near the electric or telephone pole during rain/ thunder storms.
3. Do not lean on wired fences.
4. Do not use plugged in electrical appliances.
5. Do not swim during thunder storms.
6. Stay in a pucca house with lightning conductor fitted on it.

Question 6.
Why is the upper end of the lighting conductor pointed?
Answer:

1. The pointed end makes it possible to increase the electric field near the point. The electric field set up at pointed end is high.
2. If the discharge of cloud occurs it would be easily passed through the lightening conductor to the ground and damage to the building is averted.

Question 7.
Why is coal and salt added to the pit in the ground?
Answer:
Coal and salt is filled in the pit and also there is a provision for pouring water into it. This helps to spread electric charge quickly into ground and prevent damage.

Observe the given diagram and answer the questions given.

Question a.
Name the phenomenon happening in the diagram and define it
Answer:
Phenomenon happening is static electricity.
When certain objects are rubbed against each other, they produce an electric charge on their surface at the place of friction. This is due to electrons which remain for a short time. This is called static electricity.

Question b.
What do you observe in “b” and “c” part of the diagram?
Answer:
In ‘b’, we observe attraction between the charged balloon and the uncharged aluminium ball. In ‘c’, we observe that the charge has been transferred to the aluminium ball and due to the same (like) charge, repulsion is observed.

Maharashtra State Board Class 7 Science Textbook Solutions

• The Living World: Adaptations and Classification Class 7 Science Textbook Solutions
• Plants: Structure and Function Class 7 Science Textbook Solutions
• Properties of Natural Resources Class 7 Science Textbook Solutions
• Nutrition in Living Organisms Class 7 Science Textbook Solutions
• Food Safety Class 7 Science Textbook Solutions
• Measurement of Physical Quantities Class 7 Science Textbook Solutions
• Motion, Force and Work Class 7 Science Textbook Solutions
• Static Electricity Class 7 Science Textbook Solutions
• Heat Class 7 Science Textbook Solutions
• Disaster Management Class 7 Science Textbook Solutions

Std 7 Science Chapter 1 The Living World: Adaptations and Classification Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 1 The Living World: Adaptations and Classification Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 1 The Living World: Adaptations and Classification Question Answer Maharashtra Board

1. Find my match!

Question a.

Answer:

2. Read the paragraph and answer the following questions:

I am a penguin. I live in polar region covered by snow. My abdomen is white. My skin is thick with a layer of fat underneath. My body is spindle-shaped. My wings are small. My toes are webbed. We live in flocks.

Question a.
Why is my skin white and thick and why is there a thick layer of fat underneath?
Answer:

1. White skin colour camouflage with the snow so penguins cannot be easily spotted and they get protected from enemies.
2. Thick skin and thick layer of fat underneath gives them protection from severe cold.

Question b.
Why do we live in flocks sticking close to each other?
Answer:
Penguins live in flocks sticking close to each other because sticking close to each other reduce the relative area so there is least loss of heat and they get protection from cold.

Question c.
Which geographical region do I inhabit? Why?
Answer:

1. Penguins inhabit Antarctica region. Antarctica is surrounded by ocean. Climate is colder, drier and windier.
2. It does not have human population. This climate is suitable for penguins, so they inhabit Antarctica.

Question d.
Which adaptations should you have to enable you to live permanently in the polar region? Why?
Answer:

1. I should be a warm blooded animal. This should allow me to permanently live in polar region.
2. My body has to be covered with thick fur or scale so that loss of heat will be very less and I can survive in severe cold.

3. Who is lying?

Question a.
Cockroach – I have five legs.
Answer:
Cockroach is lying. It has six legs.

Question b.
Hen – My toes are webbed.
Answer:
Hen is lying because hen’s toes are not webbed. Duck has webbed toes.

Question c.
Cactus – My fleshy, green part is a leaf.
Answer:
Cactus is lying. It’s fleshy, green part is a stem not a leaf.

4. Read each of the following statements. Write a paragraph about adaptation with reference to each statement.

Question a.
There is extreme heat in deserts.
Answer:

1. Plant’s stem is fleshy, leaves get modified into thorns to reduce loss of water. Steam perform photosynthesis in the absence of leaves.
2. Animals have cushioned soles, hump, long legs and nostrils are protected by folds of skin. Eyelashes are long and thick.

Question b.
Grasslands are lush green.
Answer:
Insects like grasshoppers have green colour so they can be camouflaged amidst grasses.

Question c.
We hide.
Answer:
In equatorial region grasses are very tall, so to protect themselves animals like tiger, elephants and deer remain hidden in these tall grasses.

Question d.
We have long ears.
Answer:
It helps the animals to receive sounds from long distance, and they can protect themselves from predators.

5. Answer the following:

Question a.
Why is the camel called the ‘ship of the desert’?
Answer:

1. Camel lives in a desert easily due to following adaptations. It has long legs and cushioned soles which keep the body of camel above the sand and cushioned soles do not allow to sink in sand while walking.
2. The nostrils are protected by folds of skin.
3. The eyelashes are long and thick.
4. It has hump which stores fats so it helps camel to survive in desert for many days without food and water.

Due to above adaptations camel is used to carry people and transport goods from one place to another place in the desert. Therefore, camel is called the ship of the desert.

Question b.
How can the plants like cactus and acacia live in deserts with scarce water?
Answer:
The plants like cactus and acacia live in deserts with scarce water due to the following adaptations.

1. Leaves are like small needles or have been modified into thorns, as a result they lose very little water by evaporation.
2. The stem stores water and food so it is fleshy.
3. The stems are green as they perform photosynthesis in the absence of leaves.
4. Their roots penetrate deep into the soil in search of water.
5. There is a thick layer of a waxy substance on the stems.

Question c.
What is the inter-relationship between adaptations of organisms and their surroundings?
Answer:
1. Adaptations of organisms depend on the changes in the surroundings.

2. To adjust with those changes in the surroundings adaptation takes place gradually and continuously in organisms.

3. Changes that take place in the various organs and life processes of organisms, enable them to live, feed, reproduce to perpetuate themselves and to protect themselves from their enemies in specific surroundings, depending upon the habitat and its geographical conditions, are called adaptations.

Question d.
How are organisms classified?
Answer:

1. Different scientists have used different criteria and independently classified plants and animals.
2. A hierarchy is formed in the classification that starts with kingdom Animalia or kingdom Plantae, further groups and sub-groups are formed depending upon basic similarities and differences.
3. This is called the ‘hierarchy of classification’.
4. Binomial nomenclature is used to identify each organism. Accordingly, a scientific name has been assigned to each organism.
5. It consists of two parts – first part is ‘genus’ and second ‘species’.
6. All identified organisms have been assigned a binomial name as per the guidelines of the International code of Nomenclature. For e.g.

Activity:

Question 1.
Find out how the gradual adaptation from primitive man to modern man must have taken place.

Class 7 Science Chapter 1 The Living World: Adaptations and Classification Important Questions and Answers

Fill in the blanks.

Question 1.
Leaves of some aquatic plants are …………. and …………. ike a ribbon.
Answer:
thin, slender

Question 2.
…………. in stems and …………. of aquatic plants are useful for floating in water.
Answer:
Air spaces, petioles

Question 3.
Leaves of desert plants are modified into …………. .
Answer:
thorns

Question 4.
The stems of desert plants are green as they perform …………. in the absence of leaves.
Answer:
photosynthesis

Question 5.
…………. roots of grasses prevent soil erosion.
Answer:
Fibrous

Question 6.
Grasses in the …………. region are very tall.
Answer:
equatorial

Question 7.
…………. are found in hilly areas as well as plains.
Answer:
Vast meadows

Question 8.
Plants need …………., …………. and …………. for growth.
Answer:
nitrogen, phosphorus, potassium

Question 9.
Dodder has …………. roots for absorbing nutrients from the host plant.
Answer:
haustorial (sucking)

Question 10.
Fungi do not have …………. so cannot perform photosynthesis.
Answer:
chlorophyll

Question 11.
Fish breathe with …………. instead of a nose.
Answer:
gills

Question 12.
Fish have …………. within the body to help them to float.
Answer:
air bladders

Question 13.
Frog and duck have …………. toes.
Answer:
webbed

Question 14.
Tigers have …………. paws.
Answer:
padded

Question 15.
Bats can fly with the help of …………. .
Answer:
patagium.

Question 16.
Desert plants are either leafless or their leaves are like …………. or modified into …………. .
Answer:
needles, thorns

Question 17.
Spring like …………. on the stems of some climbers are examples of their adaptation.
Answer:
Tendrils

Question 18.
…………. is not a sudden process, it is gradual and continuous.
Answer:
Adaptation

Question 19.
…………. proposed the theory of the survival of the fittest.
Answer:
Charles Darwin

Match the columns:

Question 1.

Answer:

Question 2.

Answer:

Name the following:

Question 1.
Animals which live in desert in deep burrows.
Answer:
Rats, snakes, spiders, lizards

Question 2.
Animals which have webbed feet.
Answer:
Frog, duck

Question 3.
Plants of snowy regions.
Answer:
Deodar, pine

Question 4.
Plants that eat insects.
Answer:
Drosera, venus flytrap, pitcher plant

Question 5.
World Frog Protection Day.
Answer:
29th April

Question 6.
2 parts of bionomial nomenclature.
Answer:
genus and species.

Who am I?

Question 1.
My leaves trap insects.
Answer:
Venus fly trap or pitcher plant.

Question 2.
I have waxy feathers and webbed feet.
Answer:
Duck

Question 3.
I breath through skin in water and through lungs on land.
Answer:
Frog

Question 4.
I have sucking roots through which I take nutrition from my host plant.
Answer:
Dodder (cuscuta)

Question 5.
I have silvery white body with thick long hair
Answer:
Snow animals like polar bear.

Question 6.
I have waxy broad leaves and air spaces in my stem.
Answer:
Lotus (or aquatic plants)

Question 7.
My Scientific name is Bos taurus.
Answer:
Cow

Question 8.
I discovered Binomial nomenclature.
Answer:
Carl Linnaeus

Question 9.
I have special thin folds in between my forelegs and hind legs called patagium.
Answer:
Bat

Question 10.
I am mango, my genus is?
Answer:
Mangifera

Say whether true or false, correct and rewrite the false statements:

Question 1.
Killing or harming frogs is prohibited by the Wild Life Protection Act.
Answer:
True

Question 2.
Scientific name of jowar is Bos taurus.
Answer:
False. Scientific name of jowar is Sorghum bicolor

Question 3.
Theory of natural selection was found by Charles Darwin.
Answer:
True

Question 4.
T.V. Channels like National Geographic, Wild and Discovery show about the feeding habits of animals.
Answer:
True

Question 5.
The spindle shaped body of birds maximizes the resistance of air while flying.
Answer:
False. The spindle shaped body of birds minimises the resistance of air while flying.

Question 6.
House lizard and monitor lizards have webbed toes.
Answer:
False. House lizard and monitor lizards have clawed toes.

Question 7.
Crocodiles use their muscles for creeping.
Answer:
True

Question 8.
The eyes of predatory carnivores are located on either side of the head.
Answer:
False. The eyes of predatory carnivores are located in the front of their head.

Question 9.
A frog is an amphibian.
Answer:
True

Question 10.
Diverse types of bushes and grasses are found in the grasslands.
Answer:
True.

Complete the given table:

Question 1.

Question 2.
Give one special adaptation or features of the following plant or animal to suit its habitat surrounding
Answer:

Who is lying?

Question 1.
Camel has thin skin and short eyelashes.
Answer:
Camel is lying – It has thick skin and long and thick eyelashes.

Answer in one or two sentences:

Question 1.
What is called ‘hierarchy of classification’?
Answer:

1. A hierarchy is formed in the classification that starts with kingdom Animalia or Kingdom Plantae, further groups and sub-groups are formed depending upon basic similarities and differences.
2. This is called the ‘hierarchy of classification’.

Question 2.
What theories were proprosed by Charles Darwin
Answer:
The theories of Charles Darwin are Theory of natural selection and theory of survival of the fittest.

Question 3.
Explain the terms Autotrophic and Parasitic
Answer:
1. Plants which are able to produce their own food with the help of the process of photosynthesis are called autotrophic plants eg. All green plants.

2. Plants which are not able to produce their own food but depend upon other plants for their nutrition are called parasitic plants They are leafless and non green in colour eg. Dodder (cuscuta). They have haustorial (sucking) roots for absorbing nutrients from the host plant.

Give scientific reasons:

Question 1.
Leaves of some aquatic plants are thin and slender like a ribbon.
Answer:
Leaves of some aquatic plants are thin and slender like a ribbon because this shape helps them to withstand fast currents of water.

Question 2.
Some aquatic plants have air spaces in stems.
Answer:
Some aquatic plants have air spaces in stems because air spaces help the plants to float on water.

Question 3.
Desert plants have thorns.
Answer:

1. Desert plants have thorns because in deserts, due to scarcity of water these plants are either leafless or their leaves are like small needles or modified into thorns.
2. They lose very little water by evaporation due to little surface area. This helps plants to survive in desert.

Question 4.
Desert plants have green stem.
Answer:
Desert plants have green stem because green stem performs photosynthesis in the absence of leaves.

Question 5.
Desert plants have strong roots.
Answer:
Desert plants have strong roots so they can penetrate deep into the soil in search of water.

Question 6.
Deodar tree is conical in shape.
Answer:
Deodar tree grows in snowy region and conical shape of the tree doesn’t allow snow to accumulate on the tree and thus protect the tree from snow.

Question 7.
Pine tree has thick bark.
Answer:
Pine tree grows in snowy region where it is extremely cold and its thick bark helps the tree to withstand the cold.

Question 8.
Plants in forest grow tall.
Answer:
In forest region variety of trees, shrubs and herbs are found. These plants compete amongst themselves for sunlight. Hence trees grow tall to get sunlight.

Question 9.
Cuscuta has haustorial roots.
Answer:

1. Cuscuta is a parasitic plant. It is leafless and cannot prepare food on its own.
2. So to get food haustorial (sucking) roots penetrate up to the conducting vessels of the host plant to absorb water and food, the Cuscuta has haustorial roots.

Question 10.
Fungi have root-like fibers.
Answer:

1. Fungi are parasitic.
2. They do not have chlorophyll and cannot perform photosynthesis.
3. So these root-like fibers help to absorb the food from the starchy foodstuffs like bhakri and bread.

Question 11.
Pitcher plant eats insects.
Answer:

1. Pitcher plant grows in a soil where nitrogen, phosphorous and potassium are very less. But the plant needs these for the growth.
2. So to fulfill the need for nitrogen, pitcher plant consumes insects.

Question 12.
Duck and frog have webbed feet.
Answer:
When duck and frog are in water at that time the webbed feet act as oars and help them to swim in water.

Question 13.
Frogs can swim easily in water.
Answer:
Frogs have webbed toes, slippery, smooth skin and triangular head. This helps the frog to swim easily through water.

Question 14.
Tiger has sharp and pointed canine teeth.
Answer:
Tiger is a carnivorous animal. So the sharp and pointed canine teeth help the tiger to tear the prey and eat.

Question 15.
Blackbuck has eyes on either side of the head.
Answer:
Blackbuck is a herbivore animal and eyes on either side of the head gives them wide angle vision which helps to protect themselves from predators.

Question 16.
Tigers have padded paws.
Answer:
Tigers are carnivorous animals. So these padded paws enable them to silently stalk their prey and capture it easily.

Question 17.
The eyes of predatory carnivores are located in the front of their head.
Answer:
The eyes of predatory carnivores are located in the front of their head because it helps them to spot their prey from a long distance.

Question 18.
Camel can live in desert.
Answer:

1. Camel can live in desert because it has thick skin to prevent loss of water from the body. Their legs are long with flat and cushioned soles.
2. The nostrils are protected by folds of skin. The eyelashes are long and thick so these adaptations enable Camels to live in desert easily.

Question 19.
White fox has white body colour.
Answer:

1. White fox lives in snowy region which throughout the year is covered with snow.
2. White colour of fox matches with the snow so it gets camouflaged in snow and it can save itself from predators.

Question 20.
Birds can fly in the air.
Answer:

1. Birds can fly in the air because the spindle shaped body minimises the resistance of air while flying.
2. Their hollow bones, body covering of feathers and forelegs being modified into wings, their body being light in weight, all these factors make the birds adapted to fly in the air.

Can you tell?

Answer the following questions:

Question 1.
Arc the plants and animals from Kashmir and Rajasthan of the same type? Can you elaborate on any differences between the two?
Answer:
Plants and animals from Kashmir and Rajasthan are of different types.
Differences in plants:

1. Plants of Kashmir, which is a snowy region, are conical in shape due to their sloping branches.
2. This shape prevents the snow accumulation on the tree and the thick bark helps the tree to withstand the cold.
3. But the plants of Rajasthan, which is a desert region, are either leafless or their leaves are small, needle shaped or have been modified into thorns. So the loss of water can be reduced
4. The stem stores water and food so they are fleshy. The stem performs photosynthesis in the absence of leaves.

Differences in animals:

1. Animals of Kashmir have thick hair and white or silver body colour camouflaged with snow. This helps them to get protection in snowy region.
2. The animals of Rajasthan have long legs with flat and cushioned soles.
3. The nostrils are protected by folds of skin. The eyelashes are long and thick. It gives protection from sand and heat.

Question 2.
In what way are sloping branches useful to plants in a snowy region?
Answer:
In a snowy region sloping branches of a plant gives conical shape to the tree and it doesn’t allow snow to accumulate on tree inspite of heavy snowfall and thus protect the tree from severe cold and snow.

Question 3.
What is the main difference between vehicles on the road and aeroplanes?
Answer:
The two main differences between vehicles on the road and aeroplanes are:

1. aeroplanes have wings whereas vehicles on the road do not have wings.
2. The body of aeroplanes are spindle shaped and the body of vehicles on the road depends on the number of wheels they have.

Use your brain power!

Answer the following questions:

Question 1.
Why does water trickle off lotus leaves?
Answer:

1. Water trickles off lotus leaves because it is coated with waxy covering on it.
2. It is one of the adaptations of aquatic plants to survive in water without getting wet and rot or sink to the bottom.

Question 2.
Why don’t the leaves of lotus plants rotinwatei?
Answer:
leaves of these plants do not rot in water because it is covered with waxy coating on it so that they do not get wet.

Question 3.
Why are roots of lotus plants short and fibrous?
Answer: –

1. These plants grow in water so the roots do not need to go deep down in search of water. Their roots are not anchored in the soil.
2. So their roots are short and fibrous.

Question 4.
The lotus stalk has holes or air spaces?
Answer:

1. The air spaces in stems and petioles of aquatic plants are useful for making them float in water and also to prevent them from rotting
2. Hence, the lotus stalk has holes or air spaces.

Answer in detail:

Question 1.
Explain the Darwin’s theory of evolution.
Answer:
Charles Darwin, a biologist suggested two principles in his theory of evolution.

1. Theory of survival of the fittest: He said that only those organisms are likely to survive which can best adapt themselves to a changing environment. This is called the theory of survival of the fittest.
2. Theory of ‘Natural selection’: If an organism is bom with a new beneficial characteristic and is able to survive, this change is preserved in the next generation. This is called the theory of ‘natural selection’.

Diagram based questions:

Draw a neat labelled diagram of fish and answer the following questions.
Answer:

Question a.
Why do fish have a body tapering towards both its ends?
Answer:
Fish have its body tapering towards its ends, to allow them to swim with least resistance in water.

Question b.
Why do Fish have transparent eyelids.
Answer:
The transparent eyelids of fish protect the eyes from the substance in the water

Question c.
How are they able to float?
Answer:
Fish have air bladders within their body which help them to float.

Observe the diagram and answer the questions.
Answer:

Question a.
What habitat does this camel live in?
Answer:
Camel lives in desert habitats or in areas where there is scarcity of water.

Question b.
State any 2 of its body adaptations to survive in desert?
Answer:

1. Thick skin to prevent loss of water from the body
2. The eyelashes are long and thin
3. Their legs are long and flat with cushioned soles

Question c.
How does a camel protect itself from sand storms or winds carrying sand?
Answer:
Camels have nostrils protected by folds of skin and long thick eyelashes to prevent entry of fir dust and sand into its nose and eyes.

Paragraph based questions:

Compare and contrast:

Question 1.
Compare the lotus plant to the Acacia plant and Hibiscus plant.
Answer:

Question 2.
What is the difference between the plants given in the pictures. Give 2 points of difference taking into consideration their adaptations with their surroundings.

Answer:

Maharashtra State Board Class 7 Science Textbook Solutions

• The Living World: Adaptations and Classification Class 7 Science Textbook Solutions
• Plants: Structure and Function Class 7 Science Textbook Solutions
• Properties of Natural Resources Class 7 Science Textbook Solutions
• Nutrition in Living Organisms Class 7 Science Textbook Solutions
• Food Safety Class 7 Science Textbook Solutions
• Measurement of Physical Quantities Class 7 Science Textbook Solutions
• Motion, Force and Work Class 7 Science Textbook Solutions
• Static Electricity Class 7 Science Textbook Solutions
• Heat Class 7 Science Textbook Solutions
• Disaster Management Class 7 Science Textbook Solutions

Std 7 Science Chapter 3 Properties of Natural Resources Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 3 Properties of Natural Resources Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 3 Properties of Natural Resources Question Answer Maharashtra Board

Fill in the blanks with the appropriate term.

Question 1.
The capacity of air to hold moisture depends upon the …………… of the air.
Answer:
temperature

Question 2.
Water does not have a …………… but has definite ………… and ………. .
Answer:
shape, volume, mass

Question 3.
While freezing, the ………….. of water is lowered.
Answer:
density

Question 4.
…………….. soil has pH 7.
Answer:
neutral

2. Why is the said that –

Question a.
Air is a homogeneous mixture of various gases.
Answer:

1. Air is made of oxygen, nitrogen, carbondioxide, water vapour and dust particles.
2. All these are in different proportions. Therefore air is a mixture.

Question b.
Water is a universal solvent.
Answer:

1. Water dissolves more substances than any other liquid. It dissolves solids, other liquids and even gases in it. Therefore, it is called as Universal solvent.
2. Water is used as a solvent in factories, laboratories, foodstuffs and in various types of biological processes occurring in the body such as digestion, excretion, etc.

Question c.
There is no alternative to water for cleaning purposes.
Answer:
Water is a universal solvent. It dissolves more substances than any other liquid so there is no alternative to water for cleaning purposes.

3. What will happen if……

Question a.
The amount of water vapour in the air increases.
Answer:
We feel the dampness or the humidity.

Question b.
Only one crop is grown repeatedly in the soil.
Answer:
The fertility of the soil decreases.

4. With whom should I pair up? 

Question a.

Answer:

5. State whether the following statements are true or false.

Question a.
Sandy soil has low capacity for holding water.
Answer:
True

Question b.
Sea water is a bad conductor of electricity.
Answer:
False. Sea water is a good conductor of electricity

Question c.
The substance in which a solute dissolves is called a solvent.
Answer:
True

Question d.
The pressure exerted by air is called atmospheric pressure.
Answer:
True

6. Explain the picture in your own words. 

Question a.
Explain the picture in your own words.

Answer:

• Diagram (a): Water is filled in the crack.
• Diagram (b): Water in the crack turns to ice due to decrease in temperature. When it turns to ice the volume increases and it expands. Due to expansion, the size of crack widens more than in diagram (a).

 7. Write answers to the following questions in your own words. 

Question a.
How is light scattered by the air?
Answer:
Air is a mixture of very fine particles of some gases, dust, smoke and moisture. When rays of light fall on these minute particles, the particles spread the light in all the directions. This natural phenomenon is called scattering of light.

Question b
Explain the various properties of water.
Answer:
Various properties of water are as follows:

1. It is a fluid substance because it can flow.
2. It does not have its own shape, it takes the shape of a container in which it is kept.
3. It has a definite volume.
4. It is a transparent liquid and it has no colour.
5. It is tasteless and odourless.
6. It is a universal solvent.

Question c.
Why is the density of seawater is more than that of rainwater?
Answer:
Seawater has many minerals dissolved in it as compared to rainwater. So due to more dissolved salts, density of seawater is more than that of rainwater.

Question d.
What is the importance of good soil structure?
Answer:
The fertility of soil depends upon soil structure. So importance of good soil structure is as follows: (a) Roots get sufficient supply of oxygen, (b) Water drainage is good therefore the roots of plants grow well.

Question e.
What are the various uses of soil?
Answer:
The uses of soil are as follows:
Plant conservation: To help plants grow. Water conservation: Soil holds water. As a result, by means of bunds and lakes, we can get water for use throughout the year.
Plasticity: (a) Soil can be given any required shape. This property of soil is called plasticity, (b) Because of its plasticity, we can use it to make articles of a variety of shapes, (c) These articles can be baked to make them hard, (d) Water storage earthen pots, earthen lamps, idols, bricks etc. are articles made from soil.

Question f.
What is the need and importance of soil testing from the point of view of farmers?
Answer:

1. The properties of the various ingredients of soil can be determined by soil testing.
2. During soil testing, the soil is examined for colour, texture and the proportion of organic matter in it.
3. Soil is tested to find out if there is a deficiency of any ingredients and to decide what measures should be taken to remove the deficiency. These information would enable the farmers to maintain the fertility of the soil.

Question g.
What is the importance of air in transmission of sound?
Answer:

1. Air is useful as a medium for the transmission of sound. Density of the air changes with temperature.
2. If the density of air increases, we can hear the sound more loud and clear.

Question h.
Why should a glass bottle completely filled with water never be kept in a freezer?
Answer:

1. Due to anomalous behaviour of water, when you cool water below 4°C, the volume of the water increases.
2. Therefore when the glass bottle completely filled with water is kept in a freezer, water expands on cooling and its volume increases so glass bottle breaks.
3. To avoid this, completely filled bottle is never kept in a freezer.

Project:

Question a.
Visit a soil testing laboratory. Learn the process of soil testing and share it with others.

Class 7 Science Chapter 3 Properties of Natural Resources Important Questions and Answers

Fill in the blanks with the appropriate term.

Question 1.
Air is a …………… of gases.
Answer:
mixture

Question 2.
Atmospheric pressure is the …………… in all the directions.
Answer:
same

Question 3.
…………… is used to measure atmospheric pressure.
Answer:
Barometer

Question 4.
As we go higher the sea level and the atmospheric pressure …………… .
Answer:
decreases

Question 5.
Pressure of air …………… when its velocity …………… .
Answer:
increases, decreases

Question 6.
…………… an effect of the difference in air pressure.
Answer:
Wind

Question 7.
The level of …………… in the air is determined by its capacity to hold water vapour.
Answer:
humidity

Question 8.
When the temperature of air is low, its capacity to hold the vapour is …………… .
Answer:
less

Question 9.
Air is useful as a …………… for the transmission of sound.
Answer:
medium

Question 10.
Water is a …………… substance.
Answer:
fluid

Question 11.
Ice is …………… than water.
Answer:
lighter

Question 12.
Density of ice is …………… than that of water.
Answer:
less

Question 13.
The space occupied by a substance is its …………… .
Answer:
volume

Question 14.
The storage of matter in a substance is its …………… .
Answer:
mass

Question 15.
The density of water is maximum at …………… °C.
Answer:
4°C

Question 16.
The substance in which the solute dissolves is called …………… .
Answer:
solvent

Question 17.
The particles of sandy soil are made of the mineral called …………… .
Answer:
silicon dioxide (quartz)

Question 18.
…………… soil has a highest water holding capacity.
Answer:
clay

Question 19.
…………… soil is red in colour.
Answer:
Terracotta

Question 20.
…………… soil is used in cosmetics.
Answer:
Multani

Question 21.
…………… is celebrated as World Soil Day.
Answer:
5th December

Question 22.
The excess of water vapour during the night or dawn is transformed into ………….. .
Answer:
dew

Question 23.
Under ordinary conditions atmospheric pressure at sea level is …………… Newtons per square mater.
Answer:
101400

Question 24.
Swedish Scientist …………… put forth the important principle that the pressure of air decreases when its velocity increases.
Answer:
Daniel Bernoulli

Question 25.
When rays of light fall on fine particles of air, the particles spread light in all the directions, this is called …………… of light.
Answer:
Scattering

Question 26.
…………… soil is easy to plough but less fertile.
Answer:
Sandy

Say whether true or false, correct and rewrite the false statements.

Question 1.
Terracotta soil is white in colour.
Answer:
False. Terracotta soil is red in colour

Question 2.
The fertility of soil depends upon soil structure.
Answer:
True

Question 3.
Multani soil is used to make statues and idols.
Answer:
False. Shadu soil is used to make statues and idols

Question 4.
Clay soil has the maximum proportion of small particles.
Answer:
True

Question 5.
Silt soil is not as ploughable as sandy soil.
Answer:
True

Question 6.
The colour of soil near land surface is darker than the colour of the lower layers.
Answer:
True

Question 7.
Kerosene is a universal solvent.
Answer:
False. Water is an universal solvent

Question 8.
The density of substance is the inter-relation between the volume and mass of a substance.
Answer:
True

Question 9.
Water is lighter than ice.
Answer:
False. Ice is lighter than water

Question 10.
Rotation of crops decreases the fertility of the soil.
Answer:
False. Rotation of crop increases the fertility of the soil.

Match the columns:

Question 1.

Answer:

Write short answers.

Question 1.
What is atmospheric pressure?
Answer:
The molecules of the gases in the air are in constant motion. When these molecules strike a body, they create pressure on that body. This pressure of air is called atmospheric pressure.

Question 2.
What is Bernoulli’s principle?
Answer:
Bernoulli’s principle is that the pressure of air ‘ decreases when its velocity increases while the pressure of air increases when its velocity decreases.

Give scientific reasons.

Question 1.
When the piston of a syringe is released, it is immediately pushed in.
Answer:

1. On pulling the piston of a syringe with the inlet hole of the syringe closed, more space becomes available to the air in the syringe, and it becomes rarified.
2. As a result, the pressure of the air in the syringe is lowered.
3. Comparatively the pressure of the outside air is very high. So when the pulled out piston is A released, it is immediately pushed in.

Question 2.
Water droplets are seen on the outer surface of a glass having ice cubes in it.
Answer:

1. Due to the ice cubes in the glass, the air surrounding the glass cools down.
2. As the water vapour in this air cools down, it condenses and gets transformed into water.
3. It is this water that collects on the outer surface of the glass.

Question 3.
Early morning dew drops are found on the grass.
Answer:

1. During the dawn (early morning) when the temperature of air is low, its capacity to hold the vapour is less.
2. At such times, the excess vapour is transformed into water droplets and we call them as dew drops.

Question 4.
During the afternoon we feel that the air is dry.
Answer:

1. In the afternoon, when the temperature of the air is high, the capacity of the air to hold the moisture also increases.
2. Then, compared to its full capacity to hold water the proportion of moisture in the air is less and we feel that the air is dry.

Question 5.
Earth’s surface remains warm and suitable for the living world on the earth.
Answer:

1. The earth receives energy from the sun. This energy is reflected by the earth in the form of heat.
2. The constituents of air surrounding the earth, such as water vapour, carbon dioxide, absorb a part of this heat and give it to the other constituents of air.
3. So the Earth’s surface remains warm and suitable for the living world on the earth.

Question 6.
We can hear the whistle of a distant train clearly early in the morning in winter.
Answer:

1. The density of air changes due to change in its temperature.
2. In winter, temperature is low so the density of the air is more. So we can hear the whistle of a distant train clearly early in the morning in winter.

Question 7.
Ice floats on water.
Answer:

1. When water freezes means it transforms into the soild state therefore its volume increases.
2. When volume increases its density decreases
3. Therefore, density of ice is less than the water, so ice floats on water.

Question 8.
In cold countries aquatic animals remain alive even after the rivers or lakes freeze in water.
Answer:
1. Due to anomalous behaviour of water, in cold countries when water gets cool and turn to ice, its volume increases, so its density decreases
2. Due to less density ice floats on water.
3.  (a) Ice is a bad conductor of heat and electricity, (b) It doesn’t allow outside heat to go from the ice to water so water temperature below the ice doesn’t change, (c) It remains as water so aquatic animals remain alive even after the rivers or lakes freeze in winter.

Question 9.
It is easier to swim in the sea than in a well or a lake.
Answer:

1. Sea water is saline. It contains salt whereas it is not so in well or a lake water.
2. Due to salts dissolved in sea water, density of sea water is more, so the swijnmer will not sink.
3. Hence, it is easier to swim in the sea than in a well or a lake.

Question 10.
Sandy soil is less fertile.
Answer:

1. Sandy soil is made up of large particles and these particles of sandy soil are made of the mineral called silicon dioxide.
2. These particles do not dissolve in water therefore soil has very little capacity to supply nutrients, so sandy soil is less fertile.

Question 11.
China clay is used for making crockery.
Answer:
China clay is used for making crockery because on heating, this clay acquires a glaze and hardness. It can be moulded into any shape and being a bad conductor of heat, it is easy to handle.

Answer the following:

Question 1.
Write the properties of air.
Answer:

1. Air is a mixture of gases.
2. Air has mass and volume.
3. It spreads in all directions.
4. It exerts pressure.
5. It is colourless.

Question 2.
Name the tests for finding out the characteristic of soil. Describe any one method of it.
Answer:
There are two tests for finding out the characteristics of soil: (1) pH (2) electrical conductivity tests.
1. pH tests: The Danish scientist Sorensen put forth the concept of pH, based on the concentration of hydrogen ions. To determine the pH of soil, a mixture of water and soil in the proportion of 1 : 2 is taken and tested using several indicators.
Accordingly, soil may be found to be one of the following types.

• Acidic soil – pH less than 6.5
• Neutral soil – pH 6.5 – 7.5
• Alkaline soil – pH higher than 7.5

2. By Electrical conductivity tests we come to know how many nutrients are present in the soil.

Question 3.
Write the causes of diminished soil fertility.
Answer:
Following are the causes of diminished soil fertility.

1. Soil pH less than 6 or higher than 8.
2. Low proportion of organic matter.
3. No proper drainage of water.
4. Repeated cultivation of the same crop.
5. Continuous use of saline water.
6. Excessive use of chemical fertilizers and pesticides.

Question 4.
Which crops reduce the fertility of soil and Which crops increase the fertility of soil?
Answer:
Wheat reduces the fertility of soil and leguminous crops like peanut, moong, moth bean, pea, lentil, Bengal gram, soyabean increase the fertility of soil.

Question 5.
Name and explain some useful types of soil.
Answer:
Following are some useful types of soil.

1. China clay (Kaolin): (a) It is white in colour, (b) It is used to make crockery, bathroom tiles, tanks, laboratory apparatus, masks, jars etc.
2. Shadu soil: (a) It is whitish in colour, (b) It is used for making statues and idols.
3. Terracotta soil: (a) This soil is red in colour, (b) Decorative articles and pots used for growing plants are made from this soil.
4. Multani soil: This soil is used in cosmetics.

Question 6.
Explain the types of soil on the basis of its texture.
Answer:
There are 3 types of soil on the basis of its texture.
1. Sandy soil: (a) Large particles are high in sandy soil, (b) Water drains rapidly through sandy soil, (c) It is easy to plough this soil, (d) It is less fertile because the particles of sandy soil are made of the mineral called silicon dioxide (quartz), (e) These particles do not dissolve in water and therefore the soil has very little capacity to supply dissolved nutrients.

2. Silt soil: (a) The particles of silt soil are of medium size, (b) Silt soil is not as ploughable as sandy soil but is much more ploughable than clay soil, (c) This soil contains a large proportion of organic materials, (d) Its capacity to supply nutrients is much greater, (e) Silt soil is also called sedimentary soil.

3. Clay soil: (a) The proportion of small particles is maximum, (b) The particles of clay soil feel smooth to touch, (c) Clay soil has a high water holding capacity.

Explain the given picture in your own words.

Question 1.

Answer:
1. The potato will sink in water as potato’s density is more than water.
2. This is the effect of density. The potato will float in salt solution as the density of salt solution is more than potato. The density of the water becomes greater due to the dissolved salt. That is why it is easier to swim in sea than in a well or a lake.

Can you tell?

Answer the following questions.

Question 1.
What change takes place in a balloon on filling air in it?
Answer:
On filling air in balloon, the shape of the balloon changes. Its size increases due to expansion.

Question 2.
Why is it easier to swim in the sea than in a well or a lake?
Answer:

1. Sea water is salty due to minerals in it. Whereas it is absent in well or a lake water.
2. Due to presence of salts, density of seawater is more than well or lake water, so it is easier to swim in the sea than in a well or lake.

Use your brain power!

Answer the following questions.

Question 1.
What is the effect of increased temperature on the pressure of air?
Answer:
Condition for closed environment:

1. When the temperature increases, the pressure of air also increases.
2. For example, as the air warms up, the molecules in the air become more active.
3. They use up more individual space even though there is same number of molecules. T1 s causes an increase in the air pressure.

Question 2.
Dip an uncorked inverted empty bottle in a slanting position into the water in a wide container. What do you observe?

Answer:

1. When an uncorked inverted empty bottle is kept slanting in the water container bubbling sound will be heard.
2. Air bubbles come out from the empty bottle and water enters the bottle.
3. Empty bottle is actually not empty but it is occupied by air.
4. When this air comes out, its place is taken by water. This shows that air occupies space.

Question 3.
In cold countries how do aquatic animals remain alive even after the rivers or lakes freeze in winter.
Answer:

1. Due to anomalous behaviour of water, in cold countries, water changes to ice.
2. Due to this change, its volume increases and density decreases. So ice floats on water.
3. Ice is a bad conductor of heat so it doesn’t allow heat to go inside so the water below ice remains as it is. So aquatic animals remain alive even after the rivers or lakes freeze in winter.

Question 4.
Why is it difficult to plough clay soil?
Answer:
It is difficult to plough clay soil because in clay soil the proportion of small particles is maximum. The particles of clay soil feel smooth to touch and has high water holding capacity, making it very difficult to penetrate through it.

Question 5.
Why is it easy to plough sandy soil?
Answer:

1. Sandy soil has large sized particles. It has weak structure due to less organic matter and large spaces between them.
2. The water also drains quickly through it making it dry and allows the plough to penetrate through it.

Question 6.
What is the water holding capacity of silt soil?
Answer:
Silt occurs as a deposit in riverbeds. The size of silt particles is between those of sand and clay. This soil also has humus in it which makes it the best soil to hold the right amount of water.

Question 7.
Which soil is suitable for cultivation? Why?
Answer:
The silt soil is suitable for cultivation.

1. The particles of silt soil is of medium size.
2. Silt soil is much more ploughable than clayey soil.
3. It contains large proportions of organic material.
4. This helps the soil in retention of water for a proper amount of time and makes it suitable for crops to grow.

Maharashtra State Board Class 7 Science Textbook Solutions

• The Living World: Adaptations and Classification Class 7 Science Textbook Solutions
• Plants: Structure and Function Class 7 Science Textbook Solutions
• Properties of Natural Resources Class 7 Science Textbook Solutions
• Nutrition in Living Organisms Class 7 Science Textbook Solutions
• Food Safety Class 7 Science Textbook Solutions
• Measurement of Physical Quantities Class 7 Science Textbook Solutions
• Motion, Force and Work Class 7 Science Textbook Solutions
• Static Electricity Class 7 Science Textbook Solutions
• Heat Class 7 Science Textbook Solutions
• Disaster Management Class 7 Science Textbook Solutions

Std 7 Science Chapter 10 Disaster Management Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 10 Disaster Management Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 10 Disaster Management Question Answer Maharashtra Board

1. Find the odd man out:

Question a.
Famine, earthquake, cloudburst, railway accident.
Answer:
Railway accident.

Question b.
Drought, heavy rains/storm, tsunami.
Answer:
Drought.

Question c.
Lava, hot mud, ash, locusts.
Answer:
Locusts.

Question d.
Washing away of crops, attack of pests on crops, volcano, singeing of crops.
Answer:
Volcano.

2. What are the remedial measures for the following calamities?

Question a.
Famine:
Answer:
Following are the remedial measures for famine:

1. Supply food and water to the people those who are dying due to hunger.
2. Give medicines to the people those who are suffering from malnutrition.
3. Government should start helping centres for the people those who are suffering from famine.
4. Give them temporary shelter in some other places where water and food are available.
5. Shift the animals to safer places.
6. Do proper planning so that region doesn’t get famine again and again.
7. Reuse water
8. grow more trees.

Question b.
Lightning strike:
Answer:
Following are the remedial measures for lightning strike:

1. Give immediate treatment to the lightning affected persons so their life can be saved.
2. Keep the people away from the open ground and swimming pool.
3. Provide them proper guidelines to cure for the lightning strike.

Question c.
Storm:
Answer:

1. Supply food, water and medicines to the people
2. Shift them to safe places.
3. Maintain peace, and advice the people not to panic.
4. Give time to time report on T.V. and radio.

Question d.
Cloudburst:
Answer:
Following are the remedial measures for cloudburst:

1. Shift people to safe places with the help of airplane, helicopter and army.
2. Supply them food, clothes, water and medicines.
3. Give time to time weather report.
4. Open more helpline centres.
5. Government should immediately send the help in terms of money and army to the people.

3. True or false? Give reasons for your answer.

Question a.
Information about a forthcoming storm is to be kept secret.
Answer:
False. Information about a forthcoming storm is not to be kept secret because, with this information we can take immediate steps for disaster management. Large scale damage of property and loss of life can be avoided.

Question b.
You should not swim when there is lightning in the sky.
Answer:
True. Lightning carries some electric charges which causes electric current in it. Water catches this current so if any person is swimming pool during lightning in the sky, then there are more chances that lightning may strike in water and the person may die due to it.

Question c.
It is possible to prevent the eruption of a volcano.
Answer:
False. It is not possible to prevent the eruption of a volcano because it is a natural event. However, by means of science and technology, it is possible to predict an eruption in advance and to take immediate steps for disaster management.

Question d.
Heavy rains result in famine.
Answer:
True. Heavy rains result in flood so crops get washed away or damaged in the flood and results in famine.

Question e.
A loud crashing sound follows a lightning.
Answer:
True, Friction and brushing happens between two clouds making them charged and lightning is produced between two clouds or one cloud and earth. The temperature increases and air pressure also increases to high amount and produces a loud sound of thunder.

4. Write answers to the following questions in our own words.

Question a.
What is a tsunami? What gives rise to a tsunami?
Answer:

1. Waves generated by an earthquake or volcano occurring on the ocean floor is called ‘tsunami’. ‘Tsunami’ is a Japanese word which means ‘harbour wave’.
2. As on land, earthquakes and volcanic eruptions occur, at the bottom of the sea, too.
3. If an earthquake occurs at the bottom of ocean, the energy released pushes the water upwards. As a result of this particular type of waves are formed.
4. These waves are not very high near the source, but they start spreading very fast to long distances.
5. The velocity of these waves is 800 to 900 km/hr. When they reach a coastal area, their velocity is reduced, but their height is found to have increased tremendously even to about 30 m. These are tsunami waves.

Question b.
What is cloudburst?
Answer:

1. Sometimes the water coming down from rain clouds does not reach the land in the form of rain. Instead, due to very high temperature near the land, it vaporizes and goes back into the same clouds.
2. As a result the amount of vapour in those clouds becomes very high.
3. Due to rapid condensation, it rains suddenly over a specific and small region at a rate of 100 mm per hour or more. This is known as a cloudburst.

Question c.
Explain the effects of a volcano.
Answer:
Following are the effects of a volcano:

1. The chemical substances such as lava, vapour, hot mud, sulphur etc. get collected on the surface of the earth and thereby mountains and hills are created
2. The atmosphere gets polluted due to the ash and gases ejected by the volcano.
3. Often, it rains as a result of a volcanic eruption.
4. The temperature rises due to hot gases.
5. Forests and settlement get buried under the hot mud.

Question d.
What are the measures to prevent loss of life due to lightning?
Answer:
Following are the measures to prevent loss of life due to lightning:

1. Do not stand on open ground, below a tree, on high location, near an electric pole, near a telephone pole or a tower etc.
2. Do not lean on wire fences around a farm, a compound, a garden or a house.
3. If you are on two-wheeler, a bicycle, a tractor or a boat, get off immediately and go to safe place.
4. Do not gather all together in one place.
5. Take care to keep a distance of 15 feet between any two persons.
6. Do not use plugged in electrical appliances. Do not use a mobile or telephone.
7. Stand on dry wood, a plastic sheet, sack or jute cloth or dry leaves.
8. Keeping your feet together support yourself on the soles of your feet placing your hands on your knees and crouch low.
9. Swimmers and fishermen should immediately come out of the water.
10. A pucca house is the safest place. Find out if there is a lightning conductor on any tall building near your house. If necessary get a lightning conductor fitted on your house.

5. What measures have been taken to deal with calamities such as floods and landslides under the disaster management programme in Maharashtra?

Question a.
What measures have been taken to deal with calamities such as floods and landslides under the disaster management programme in Maharashtra?
Answer:
In Maharashtra, all districts have their own disaster management plan to deal with calamities such as floods and landslides.

1. The plan deals extensively with the emergency, and evacuation measures to be taken up in cases of flood and landslide.
2. The district-level disaster management plan has detailed information about geographical details, population, flood-prone areas, villages and other macro details.
3. Nearly 14 such key departments are engaged in disaster mitigation measures and each one has been assigned a specific task to do at times of natural disasters.
4. The administration is now training master trainers at the district level who in turn will train key persons at village and taluka levels to deal with a natural disaster.
5. The administration through radio jingles, public advertisements and other measures is informing people about how to react at times of flood and landslide.
6. Currently, the Indian Meteorological Department (IMD) gives weather forecast on daily basis and for the next 5 days with advice to farmers on when to start crop sowing and harvesting etc.

6. With reference to disaster management what are the things in your house that you will check?

Question a.
With reference to disaster management what are the things in your house that you will check?
Answer:
With reference to disaster management, we should keep the following things at home and check regularly.

1. Keep proper first aid kit at a handy place.
2. Keep all the electric connections in proper condition.
3. Keep the gas line or tube connection proper.
4. Keep self-powered flashlights and self-powered radios.
5. Keep non-perishable food which will last for a week.
6. Keep a fire extinguisher handy and in proper condition.
7. Keep updated telephone diary which should have emergency phone numbers.

Project:

Question 1.
With the help of the Internet, collect information about the places where a calamity has occurred.

Question 2.
Collect information from the Internet about how cyclonic storms are named.

Class 7 Science Chapter 10 Disaster Management Important Questions and Answers

Fill in the blanks:

Question 1.
………… and ………… disasters are related to each other.
Answer:
Natural manmade.

Question 2.
………… implemented a canal scheme for drinking water in Aurangabad.
Answer:
Malik Ambar.

Question 3.
………… has turned out to be the most famine-affected contents of the world.
Answer:
Asia

Question 4.
The government of India established the ………… in 1976.
Answer:
National Flood Commission

Question 5.
The ………… that occurred in Mumbai on 26th August 2005 was extraordinary and unforgettable.
Answer:
cloudburst.

Question 6.
A cloudburst occurred at ………… on 6th August, 2010.
Answer:
Ladakh (Leh)

Question 7.
About ………… lightning flashes occur per second in the atmosphere.
Answer:
40.

Question 8.
The temperature generated by ………… is higher than that of the sun.
Answer:
lightning

Question 9.
When some substances comes out of the earth’s crust in an eruption and start flowing is called a ………… .
Answer:
volcano

Question 10.
Some islands are created due to the eruption, of ………… in the sea.
Answer:
volcano

Question 11.
………… is a Japanese word which means ‘harbour wave’.
Answer:
Tsunami.

Question 12.
About ………… nations from all over the world are members of the UNDP.
Answer:
177.

Question 13.
………… established a standing international organization UNDP in 1965.
Answer:
United Nations.

Question 14.
………… is celebrated as International Day for Disaster Reduction.
Answer:
13th October

Question 15.
The condition that arises due to long term and severe scarcity of food grains and water is called………. .
Answer:
famine

Can you tell?

Question 1.
Is it possible to prevent the loss of life caused by lightning?
Answer:
Yes, it is possible to prevent the loss of life caused by lightning, by taking precautions.

Question 2.
What should be done to prevent the bunds on a farm from getting washed away in the rainy season?
Answer:

1. Grow more trees near the bunds.
2. Grow grass strips.
3. Make stone lines near the bunds.
4. Use contour ploughing and tillage network method to prevent the bunds on a farm from getting washed away in the rainy season.

Question 3.
Why do we experience water scarcity?
Answer:
Lessor no rain leads to water scarcity.

Question 4.
What causes rain?
Answer:

1. Due to heat of the sun, water from the sea, lake and river gets evaporated and this water vapour is light in weight so it goes higher and higher and forms the cloud.
2. At a certain level the amount of vapour in those clouds becomes very heavy and it burst and rain occurs.

Question 5.
Have you seen a flash of lightning in the sky? When?
Answer:
Students will answer this question based on their experience.

Question 6.
What causes lightning?
Answer:

1. Where air and clouds rub against each other in the sky, the upper part of some clouds on the upper side becomes positively charged and the lower sides become negatively charged.
2. When this negative charge on the bottom of the cloud becomes much larger than the charge on the ground it starts flowing towards the ground in stages.
3. This happens very fast, in much less than a second and heat, light and sound energy are produced along with the electric current.

Use your brainpower!

Answer the following questions:

Question 1.
We should not wait at the foothill while it is raining heavily.
Answer:
During heavy rain there are chances of landslide and flood, so we should not wait at the foothill while it is raining heavily.

Maharashtra State Board Class 7 Science Textbook Solutions

• The Living World: Adaptations and Classification Class 7 Science Textbook Solutions
• Plants: Structure and Function Class 7 Science Textbook Solutions
• Properties of Natural Resources Class 7 Science Textbook Solutions
• Nutrition in Living Organisms Class 7 Science Textbook Solutions
• Food Safety Class 7 Science Textbook Solutions
• Measurement of Physical Quantities Class 7 Science Textbook Solutions
• Motion, Force and Work Class 7 Science Textbook Solutions
• Static Electricity Class 7 Science Textbook Solutions
• Heat Class 7 Science Textbook Solutions
• Disaster Management Class 7 Science Textbook Solutions

Std 7 Science Chapter 6 Measurement of Physical Quantities Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 6 Measurement of Physical Quantities Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 6 Measurement of Physical Quantities Question Answer Maharashtra Board

1. Write answers to the following questions in your own words:

Question a.
Why is the weight of the same object different on different planets?
Answer:
The weight of the same object is different on different planets because weight depends on the gravitational force of the planet and gravitational force on every planet is different so the weight also differs from planet to planet.

Question b.
What precautions will you take to make accurate measurements in day-to-day affairs?
Answer:
Following precautions will be taken to make accurate measurements in day to day affairs:

1. The balance should carry the stamp of standardisation by the department of weights and measures.
2. Balance should be stable and the pointer of the balance should be upright.
3. The underside of the pan should not be tampered with any other weight or layers of other metal.
4. The weight should be made of metal.

Question c.
What is the difference between mass and weight?
Answer:

2. Who is my companion? 

Class 7 Science Chapter 6 Measurement Of Physical Quantities Exercise Question 1.

Answer:

3. Explain giving examples. 

Question a.
Scalar quantity:
Answer:
A quantity that can be completely expressed by its magnitude alone is called a scalar quantity, e.g. length, breadth, area, mass, temperature, density, time, work. In all these examples a value with a unit is used to express quantities. Thus, we say that the length of a tunnel is 2 km.

Question b.
Vector quantity:
Answer:
The quantity that is expressed completely only.’ v when magnitude and direction are both given is called a vector quantity. Displacement, velocity are vector quantities e.g. a displacement of 20 km towards north, the aeroplane flying at a velocity of 500 km/hr towards Mumbai.

4. Explain, giving examples, the errors that occur while making measurements.

Question a.
Explain, giving examples, the errors that occur while making measurements.
Answer:
Major causes of errors in measurement are:

1. Not using the appropriate device.
2. Not using the device properly.

Example: While buying things at grocery shops and the vegetable market remember to look out for the following:

• The balance should carry the stamp of standardisation by the department of weights and measures.
• Balance should be stable. The pointer of the balance should be upright.
• No changes should be done on the underside of the pan of the balance.
• Weight should be made up of metals and it has to be standardized.

5. Give reasons:

Question a.
It is not proper to measure quantities by using body parts as units.
Answer:
It is not proper to measure quantities by using body parts as units because length of the body parts changes from person to person, so accurate measurement can not be found with the body parts as units.

Question b.
It is necessary to get the weights and measures standardized at regular intervals.
Answer:
It is necessary to get the weights and measures standardized at regular intervals because of that accurate weight and measurement can be taken. Errors will be avoided.

6. Explain the need for accurate measurement and the devices to be used for that.

Question a.
Explain the need for accurate measurement and the devices to be used for that.
Answer:

1. Measurement of substances that are precious or of great importance and used in very small quantities is done meticulously and accurately.
2. Due to advancements in technology, devices that measure very small magnitudes of quantities like distance, mass, time and temperature are available now.
3. e.g. distance and time in connection with very important sports competitions, mass of gold, body temperature etc.
4. Devices to be used for this are thermometer, digital balance (Analytical balance) etc.

Project:

Class 7 Science Chapter 6 Measurement Of Physical Quantities Question 1.
Collect information about various physical quantities used in day-to-day life and the devices used for their measurement.

Class 7 Science Chapter 6 Measurement of Physical Quantities Important Questions and Answers

Fill in the blanks:

Std 7 Science Chapter 6 Measurement Of Physical Quantities Question 1.
The amount of matter present in a substance is called ………………. .
Answer:
mass

Measurement Of Physical Quantities Class 7 Exercise Question 2.
…………. is the qualitative measure of the inertia of an object.
Answer:
mass

6. Measurement Of Physical Quantities Question 3.
The larger the mass, the ……………. is the inertia.
Answer:
greater

6.Measurement Of Physical Quantities Question 4.
Mass is a …………… quantity.
Answer:
scalar

Physical Quantities And Measurement Class 7 Question 5.
…………… does not change from place to place anywhere in the world.
Answer:
mass

Measurement Of Physical Quantities Class 7 Question 6.
The gravitational force that acts on a mass is called its ……………. .
Answer:
weight

6 Measurement Of Physical Quantities Question 7.
Wright is a …………… quantity.
Answer:
vector

Question 8.
System International (SI) is also called ………….. .
Answer:
metric system

Question 9.
In Egypt in ancient times, the distance from a man’s elbow to the tip of his middle finger was called a ………… .
Answer:
cubit

Question 10.
Gold was weighed in a unit called …………… .
Answer:
gun

Who is my companion?

Question 1.

Answer

Say whether true or false. Correct and rewrite the false statements:

Question 1.
The standards of the six fundamental units are kept in the National Physical Laboratory at New Delhi.
Answer:
True

Question 2.
Matter has a natural tendency to resist a change in its state, which is called inertia.
Answer:
True

Question 3.
Weight and mass are both equal quantities.
Answer:
False. Weight and mass are both different quantities

Question 4.
Work is a vector quantity.
Answer:
False. Work is a scalar quantity

Question 5.
Velocity is a scalar quantity.
Answer:
False. Velocity is a vector quantity

Question 6.
Unit of time in both the systems is second.
Answer:
True

Question 7.
Unit of mass in C.G.S. system is kilogram
Answer:
False. Unit of mass in C.G.S. system is gram

Question 8.
Symbol of unit of second is sec.
Answer:
False. Symbol of unit of second is ‘s’

Question 9.
1 cubic foot means 28.317 ml
Answer:
False. 1 cubic foot means 28.317 litres.

Question 10.
Vector quantity requires magnitude only.
Answer:
False. Vector quantity required magnitude and direction both.

Give scientific reasons:

Question 1.
Weight of our body on the moon is less than that on the earth.
Answer:

1. Gravitational power of moon is less than the earth.
2. Weight depends on the gravitational power of that place.
3. Since the gravitational power of the moon is less than that of the earth, the weight on moon is less than that on the earth.

Question 2.
Mass is a scalar quantity
Answer:
Mass is a scalar quantity because it can be completely expressed by its magnitude alone, so it is scalar quantity.

Question 3.
Weight is a vector quantity.
Answer:
Weight can be expressed completely only when magnitude and direction are both given so weight is a vector quantity.

Distinguish between the following:

Question 1.
Scalar quantity and Vector quantity
Answer:

Question 2.
M.K.S. system and C.G.S. system
Answer:

Define the following:

1. Mass: The amount of matter present in a substance is called mass.
2. Inertia: Matter has a natural tendency to resist a change in its state, which is called Inertia.
3. Weight: The gravitational force that acts on the mass is called its weight.
4. Physical Quantities: The quantities in day to day life which can be measured are called physical quantities.
5. Standardization: The process of checking things against a standard measure from time to time is called standardization.

Write answers to the following questions in your own words.

Question 1.
What is an atomic clock?
Answer:
An extremely accurate type of clock which is regulated by the vibrations of an atomic or molecular system such as caesium atom or ammonia is called atomic clock. It is used to maintain standard times of countries accurately.

Answer the following questions:

Question 1.
Why would the weight of an object be; maximum at the poles and minimum at the equator?
Answer:

1. The gravitational force that acts on the mass is called the weight.
2. The earth is not exactly spherical, it flattens at the poles.
3. As the distance increases the gravitational force decreases.
4. Therefore due to reduced distance at the poles compared to the equator, the weight is maximum at the poles than equator.

Question 2.
Why is the weight of an object at a high altitude less than its weight at the sea-level?
Answer:

1. The gravitational force that acts on the mass is called the weight.
2. The gravitational force is always inversely proportional to the distance.
3. So as the distance increases between the earth and the object, the gravitational force decreases.
4. The gravitational force by which the earth attracts an object towards its centre is called weight.
5. The weight at the sea-level is higher than at higher altitude, as the object is at a greater distance at higher altitudes compared to sea-level.

Maharashtra State Board Class 7 Science Textbook Solutions

• The Living World: Adaptations and Classification Class 7 Science Textbook Solutions
• Plants: Structure and Function Class 7 Science Textbook Solutions
• Properties of Natural Resources Class 7 Science Textbook Solutions
• Nutrition in Living Organisms Class 7 Science Textbook Solutions
• Food Safety Class 7 Science Textbook Solutions
• Measurement of Physical Quantities Class 7 Science Textbook Solutions
• Motion, Force and Work Class 7 Science Textbook Solutions
• Static Electricity Class 7 Science Textbook Solutions
• Heat Class 7 Science Textbook Solutions
• Disaster Management Class 7 Science Textbook Solutions

Std 7 Science Chapter 2 Plants: Structure and Function Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 2 Plants: Structure and Function Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 2 Plants: Structure and Function Question Answer Maharashtra Board

1. Give examples of 3 plants that have:

Question a.
Spiny fruits
Answer:
Jack fruit, Pineapple, Lychee (litchi), Datura

Question b.
Spiny stem
Answer:
Cactus, Wild rose, Catclaw acacia, Silk, Cotton

Question c.
Red flowers
Answer:
Rose, Dahlia, Hibiscus, Tulips,

Question d.
Yellow flowers
Answer:
Marigold, Daffodil, Sunflower, Daisy

Question e.
Leaves which close at night
Answer:
Mimosa plant, Tallwood, Prayer plant, Gulmohar

Question f.
Single seeded fruits
Answer:
Mango, Lychee, Jamun

Question g.
Many seeded fruits
Answer:
Custard apple, Papaya, Watermelon.

2. Observe any one flower and its various parts and describe it in your own words.

Question a.
Answer:

A flower has following parts:
1. Pedicel: (a) Flower may have a long or a short stalk called pedicel, (b) One end of the pedicel is attached to the stem, (c) The other end of the pedicel is expanded and swollen. It is called the receptacle, (d) Petals and other parts of the flower are supported on the receptacle.
2. Calyx: In the bud condition, the petals are covered by leaf like parts called sepals which are green in colour. They form the calyx.
3. Corolla: This is made up of colourful parts called petals.
4. Androecium: (a) This is the male reproductive part of the flower, (b) It consists of stamens, (c) Each stamen is made up of anther and filament.
5. Gynoecium: (a) This is the female reproductive part of the flower, (b) This is made up of carpels, (c) A carpel consists of stigma, style and ovary.

3. What are the similarities and differences between?

Question a.
Jowar and Moong
Differences:

Similarities:
Jowar and Moong both are angiosperms.

Question b.
Onion and Coriander
Differences:

Similarities:

1. Both are used in cooking.
2. Both are edible.
3. Both belongs to kingdom plantae.

Question c.
Leaves of banana and Leaves of mango
Answer:

Question d.
Coconut tree and Jowar stalk plant
Answer:
Differences:

Similarities:

1. Both are from same kingdom plantae.
2. Both are autotrophic.
3. Both are monocotyledonous plants.

4. Explain the following images in your own words.

Question a.

Answer:

1. Diagram A is of maize seed. It is a monocotyledonous seed and does not divide into two equal parts. The plant has fibrous root system.
2. Diagram B is of bean seed. It is a dicotyledonous seed and it divides into two equal parts. The plant has tap root system.

5. Describe the functions of various parts of a plant.

Question a.
Describe the functions of various parts of a plant.
Answer:
The functions of various parts of a plant are as below.
1. Root: (a) Fixation: It anchors the plant body to the soil, so helps in fixation, (b) Absorption: It absorbs water and nutrients from the soil, so helps in absorption, (c) Conduction: The root translocates water and mineral salts into the stem. (d) Storage: A certain amount of food is stored in the root which is utilized as it grows.
(e) Preventing soil erosion: It helps to bind the soil particles and prevent them from being blown away by wind or water.
2. Stem: (a) It supports and holds leaves, flower and fruits, (b) The stem conducts the water and minerals from roots to leaves and fruits, (c) It stores the food.
3. Leaves: (a) It synthesizes food for the plant, (b) Stomata, the tiny openings in the leaf help in gaseous exchange and are responsible for the process of transpiration.
4. Flower: It helps in pollination.
5. Fruit: (a) It protects the seed, (b) It helps in seed dispersal.
6. Seed: A new plant develops from it.

6. Certain properties are mentioned below. Find a leaf corresponding to each property and describe those plants.

Question a.
Certain properties are mentioned below. Find a leaf corresponding to each property and describe those plants.
leaves with smooth surface, leaves with rough surface, fleshy leaf, spines on leaf.
Answer:

1. Leaves with smooth surface: e.g. Banana leaf. It is large in size. It is closely rolled up one over the other. Together they look like a trunk but they form only an apparent trunk. It has parallel venation.
2. Leaves with rough surface: e.g. Hibiscus leaf. It has reticulate venation. Leaf margin is toothed.
3. Fleshy leaf: e.g. Jade plant, water hyacinth. It has fleshy, glossy and smooth leaves. They are coloured jade green and having a slightly red tinge towards the edge of leaves when exposed to higher level of light.
4. Spines on leaf: e.g. Opuntia, Ci/cas, kevda. Opuntia is a desert plant. Leaf is thick, fleshy and having spines on it.

7. Find the plant parts.

Question a.

Answer:

ROOT, ROOT CAP, ROOT HAIR, BUD, PETALS, STEM, RADICLE, FLOWER, LEAF, VEIN, CALYX, NODE, OVUM.

Class 7 Science Chapter 2 Plants Structure And Function Question Answer Activity:

Sketch various types of leaves in Paintbrush on the computer and save the sketches in a folder of your own name.

Class 7 Science Chapter 2 Plants: Structure and Function Important Questions and Answers

Plants Structure And Function Exercise Fill in the blanks:

Plants Structure And Function Class 7 Questions And Answers Question 1.
The part that grows from inside the seed towards the soil is called the …………….. .
Answer:
radicle

Plants Structure And Function Class 7 Question 2.
The part that grows above the soil from the seed is called the …………….. .
Answer:
plumule

Plants Structure And Function Question And Answer Question 3.
The part of the plant growing below the soil from radicle for support is called …………….. .
Answer:
root

Plants Structure And Function Class 7 Exercise Question 4.
The …………….. protects the root-tip from injuries.
Answer:
root cap

Plants Structure And Function Exercise Question 5.
Roots bearing hair like processes near the root tips are called …………….. .
Answer:
root hairs

Class 7 Science Chapter 2 Plants Structure And Function Question Answer Question 6.
Thread-like or fibre like roots arising from the stem are called ……………. .
fibrous roots

Question 7.
The stem grows above the soil from the …………….. of the sprouting seed.
Answer:
plumule

Question 8.
Leaves come out at the …………….. .
Answer:
nodes

Question 9.
The part of the stem between two nodes is called …………….. .
Answer:
inter node

Question 10.
The tip or the apical end of the stem is called a …………….. .
Answer:
bud

Question 11.
The broad, spread out part of the leaf is called the …………….. or …………….. .
Answer:
leaf blade, lamina

Question 12.
The tip of the leaf is called the …………….. .
Answer:
leaf apex

Question 13.
Leaves of some plants have a stalk called a …………….. .
Answer:
petiole

Question 14.
The portion of the leaf attached to the stem is called the …………….. .
Answer:
leaf base

Question 15.
Small leaf like structures near the leaf base is called …………….. .
Answer:
stipides

Question 16.
Flowers may have a long or a short stalk called …………….. .
Answer:
pedicel

Question 17.
One end of the pedicel is attached to the …………….. .
Answer:
stem

Question 18.
…………….. is a male reproductive organ of the flower.
Answer:
Androecium

Question 19.
…………….. is a female reproductive organ of the
Answer:
gynoecium

Question 20.
Androecium consists of …………….. .
Answer:
stamens

Question 21.
Gynoecium consists of …………….. .
Answer:
carpels

Question 22.
Seeds which get divided into two equal parts are called …………….. seeds.
Answer:
dicotyledonous

Question 23.
Seeds which do not divide into two equal parts are …………….. called seeds.
Answer:
monocotyledonous

Question 24.
Petals and other parts of the flower are supported on the …………….. .
Answer:
receptacle

Question 25.
Sepals are …………….. in colour.
Answer:
green.

Match the columns:

Question  1.

Answer:

Question 2.

Answer:

Question 3.

Answer:

Say whether True or False Correct and rewrite the false statements:

Question 1.
Stem grows from radicle.
Answer:
False. Stem grows from the Plumule

Question 2.
Leaf margins may be entire, dentate or lobed.
Answer:
True

Question 3.
The leaf blade of leaves in some plants is divided into many small parts called leaflets.
Answer:
True

Question 4.
Maize plant has reticulate venation.
Answer:
False. Maize plant has parallel venation

Question 5.
A carpel consists of stigma, style and ovary.
Answer:
True.

Question 6.
A stamen is made up of nodes and internodes.
Answer:
False. A stamen is made up of anther filament

Question 7.
The ovary develops into a fruit.
Answer:
True

Question 8.
Fertilized ovules form the seeds.
Answer:
True

Question 9.
A mango fruit contains many seeds.
Answer:
False. A mango fruit contains only one seed

Question 10.
A fruit like cashew have seed outside the fruit.
Answer:
True.

Question 11.
Leaves of some plants do not have a petiole.
Answer:
True

Question 12.
The peepal leaf has parallel venation.
Answer:
False. It has reticulate venation.

Find the odd one out:

Question 1.
Pea, Moong, maize, groundnut
Answer:
Maize – Its seed is monocotyledonous, while others have dicotyledonous seeds.

Question 2.
Cashew, apple, mango, chikoo
Answer:
Cashew – Its seed is outside the fruit, others have internal seeds.

Question 3.
Stigma, anther, style, ovary
Answer:
Anther – It is a part of androecium, while others are a part of gynoecium.

Question 4.
Petiole, vein, calyx, apex
Answer:
Calyx – It is a part of flower, whereas others are parts of leaf.

Question 5.
Aerial, stilt, runner, lobed
Answer:
Lobed – It is a type of leaf margin, while others are types of modified roots.

Answer the following in one or two sentences:

Question 1.
Which types of roots do the fenugreek, spinach and onion plants have?
Answer:

1. Fenugreek and spinach have tap roots with a few secondary roots whereas onion has fibrous root.
2. Fenugreek roots also have some nodules which contain nitrogen fixing bacteria.

Question 2.
What are called prop roots?
Answer:
Roots emerging from the trunk and branches of a banyan tree grow towards the soil. These roots are called prop roots.

Question 3.
What is called reticulate venation?
Answer:

1. A leaf is divided into two equal parts by a single mid-vein which lies along the midline of the leaf blade.
2. Secondary veins arise from the mid-vein. They are branched and form a network or reticulum. Such a type of venation is called reticulate venation.

Question 4.
What is called parallel venation?
Answer:
In a leaf all the veins are parallel, running from the leaf base to the leaf apex. Such a venation is called parallel venation.

Question 5.
What is pollination?
Answer:
After maturity, anthers burst and the pollen grains which are released fall on the stigma. This process is called pollination.

Question 6.
Why are the underground parts of plants like radish, carrot, beet and sweet potato thick, fleshy and swollen? Which parts of the plant are they?
Answer:
The underground parts of plants like radish, carrot, beet and sweet potato are thick, fleshy and swollen because they store food in the form of starch. These are the root part of the plant.

Distinguish between:

Question 1.
Tap roots and fibrous roots.
Answer:

Question 2.
Dicotyledonous seeds and monocotyledonous seeds.
Answer:

Draw neat and labelled diagram for the following:

Question 1.
Tap root
Answer:

Question 2.
Parts of a leaf.
Answer:

Question 3.
Parts of stem
Answer:

Do as directed:

Question 1.
Certain properties are mentioned below. Find a leaf corresponding to each property and describe those plants.
Answer:

1. Leaves with smooth surface: e.g. Banana leaf. It is large in size. It is closely rolled up one over the other. Together they look like a trunk but they form only an apparent trunk. It has parallel venation.
2. Leaves with rough surface: e.g. Hibiscus leaf. It has reticulate venation. Leaf margin is toothed.
3. Fleshy leaf: e.g. Jade plant, water hyacinth. It has fleshy, glossy and smooth leaves. They are coloured jade green and having a slightly red tinge towards the edge of leaves when exposed to higher level of light.
4. Spines on leaf: e.g. Opuntia, Cycas, kevda. Opuntia is a desert plant. Leaf is thick, fleshy and having spines on it.

Use your brainpower!

Answer the following questions:

Question 1.
What would have happened if plants like tamarind, banyan and mango had fibrous roots?
Answer:
If plants like banyan, mango, tamarind had fibrous roots they would get uprooted and fall even with a little strong wind as the roots would not be able to support and anchor the trees firmly.

Question 2.
What will happen if the root-tip is injured?
Answer:

1. Root cap helps the root to grow downward It protects the sensitive part of the root and eases the movement of the root through the soil.
2. Injury of the root tip causes the root to grow randomly and it also may lead to injury of the sensitive part of the root.

Question 3.
Which types of roots do the fenugreek, spinach and onion plants have?
Answer:

1. Fenugreek and spinach have tap roots with a few secondary roots whereas onion has fibrous root.
2. Fenugreek roots also have some nodules which contain nitrogen-fixing bacteria.

Question 4.
Of what use to a plant are the insects flitting about around its flowers?
Answer:

1. The insects try to suck the nectar from the flowers and in that process the pollen grains stick to their legs.
2. When they sit on another flower the pollen grain stick to the stigma and the pollination takes place. Thus, these insects help in the pollination.

Observe the figure and answer the questions given.

1.

Question a.
What is shown in the picture?
Answer:
The picture shows the arrangement of leaves on the stem.

Question b.
What arrangement is shown in (A), (B), and (C)?
Answer:
(A) Alternate (B) Opposite (C) Whorled

2.

Question a.
Lable parts 1 to 6.
Answer:

1. Gynoecium or carpel
2. Corolla
3. Androecium (Stamen)
4. Ovary
5. Corolla
6. Pedicel

Question b.
Name the female reproductive part.
Answer:
Gynoecium

Question c.
Name the colourful part of the flower.
Answer:
Corolla

Question d.
Which part develops into fruit?
Answer:
Ovary

Question e.
Which pa pollination?
Answer:
The transfer of pollen grains from the anther to the stigma of flower is called pollination.

Maharashtra State Board Class 7 Science Textbook Solutions

• The Living World: Adaptations and Classification Class 7 Science Textbook Solutions
• Plants: Structure and Function Class 7 Science Textbook Solutions
• Properties of Natural Resources Class 7 Science Textbook Solutions
• Nutrition in Living Organisms Class 7 Science Textbook Solutions
• Food Safety Class 7 Science Textbook Solutions
• Measurement of Physical Quantities Class 7 Science Textbook Solutions
• Motion, Force and Work Class 7 Science Textbook Solutions
• Static Electricity Class 7 Science Textbook Solutions
• Heat Class 7 Science Textbook Solutions
• Disaster Management Class 7 Science Textbook Solutions

Std 7 Science Chapter 9 Heat Question Answer Maharashtra Board

Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 9 Heat Notes, Textbook Exercise Important Questions and Answers.

Class 7 Science Chapter 9 Heat Question Answer Maharashtra Board

Fill in the blanks:

Question a.
Maximum heat is absorbed by a ………….. coloured object.
Answer:
black

Question b.
……………. of heat does not require a medium.
Answer:
Radiation

Question c.
Conduction of heat takes place through a ……………. substance.
Answer:
solid

Question d.
The shining surface in a thermos flask decreases the outgoing heat by ……………… .
Answer:
reflection

Question e.
Cooking utensils are made from metals due to their property of ……………… .
Answer:
conduction

Question f.
The earth receives heat from the sun by ………………. .
Answer:
radiation

2. What will absorb heat?
Steel spoon, wooden board, glass vessel, iron griddle (lava), glass, wooden spoon, plastic plate, soil, water, wax.

Question a.
What will absorb heat?
Steel spoon, wooden board, glass vessel, iron griddle (lava), glass, wooden spoon, plastic plate, soil, water, wax.
Answer:
Following will absorb heat fast: steel spoon, iron griddle, water, wax. Remaining objects also obsorb heat but very slowly.

3. Write Answers to the following questions. 

Question a.
How does a fever get lowered by putting a cold compress on the forehead of a patient?
Answer:
The water in the cold compress will evaporate by the heat of fever thus taking some local heat of the body and temperature of the body is lowered, therefore the fever gets lowered by putting a cold compress on the forehead of a patient.

Question b.
Why are the houses in Rajasthan painted white?
Answer:
Rajasthan being a desert, temperature is very high. So there is excess heat. White colour doesn’t absorb the heat but reflects back, so houses will not become hot due to excess heat and inside of the house will be cool. So the houses in Rajasthan are painted white.

Question c.
What are the modes of heat transfer?
Answer:
There are three modes of heat transfer:

1. conduction
2. convection
3. radiation.

Question d.
Explain which mode of heat transfer causes sea breezes and land breezes?
Answer:

1. Unequal heating of air above the sea and land sets up convection currents which cause sea breezes during the day time.
2. The land near the sea is heated by sunlight to a higher temperature than the sea.
3. As the air above the land is heated, it becomes lighter and moves upwards, its place is then taken by cooler air moving from the sea towards the land.
4. Sea breezes are thus set up. At night, the land cools faster than water in the sea. Therefore air above sea water is hotter than air above the land.
5. So cooler air from the land moves towards the sea forming land breeze.

Question e.
Why is the outer coat of the penguins of Antarctica black?
Answer:
The outer coat of the penguins of Antarctica is black because black colour absorbs heat so penguins get lots of heat due to this black colour and they can live easily in very, very cold Antarctica region.

Question f.
Why are heaters fitted near the floor and air conditioners near the ceiling of a room?
Answer:
1. Due to air conditioners, air becomes cool so its density increases and it becomes heavy. So it goes down and warm air with less density comes up and take the place of cold air. This cycle goes on and on and the whole room becomes cool.
2. If it is fitted near the floor then cool air of high density can’t go up and upper air with low density cannot come down and cooling of the room does not take place properly so air conditioners are fitted near the ceiling of a room.
3. Heaters are fitted near the floor. Due to heating, air becomes hot which is lighter than cold air. So it goes up and upper air with high density comes down.
4. This cycle goes on and on and the full room becomes warm. So heaters are fitted near the floor.

4. Give scientific reasons.

Question a.
An ordinary glass bottle cracks when boiling water is poured into it, but a borosil glass bottle does not.
Answer:

1. An ordinary glass bottle cracks when we pour boiling water into it because there is a lot of temperature difference between the inner and outer parts of the glass.
2. The inner part gets hot and expands while the outer part remains cold since glass is a bad conductor of heat.
3. This unequal expansion causes the crack of glass bottle.
4. But the borosil glass bottle has a very high melting point so the temperature difference is very less, hence it doesn’t crack.

Question b.
The telephone wires which sag in summer become straight in winter.
Answer:

1. Telephone wires are made up of copper metal. Metals expand on heating.
2. In summer the copper wire expands, thus the length of the wire increases between the two poles and instead of remaining straight it sags.
3. In winter due to cold, it contracts and comes back to the original position, so it becomes straight in winter.

Question c.
Dewdrops form on the grass in winter.
Answer:

1. During the winter, the temperature of air is low, its capacity to hold the vapour is less.
2. At such times the excess water vapour is transformed into water droplets due to cold. And so the dew drops form on the grass in winter.

Question d.
In winter, why does an iron pillar feel colder than a wooden pole.
Answer:

1. Iron is a metal and metals are very good conductors of heat so it transfers heat at a much faster rate than wood.
2. That means, when we touch them, metals conducts away energy in the form of heat emitted by our hand and temperature of our hand lowers down and we get a cold’ sensation.
3. This is what makes the metal appear colder than the wood.
4. The wood is taking away heat at a much slower rate.

Project:

Question 1.
Make a note of the various examples of heat transfer seen in day-to-day life.

Class 7 Science Chapter 9 Heat Important Questions and Answers

Fill in the blanks:

Question 1.
………………… is an indicator of the heat in a substance.
Answer:
Temperature

Question 2.
………………. flows from higher temperature to lower temperature.
Answer:
Heat

Question 3.
Transfer of heat from one place to another takes place by ……………. or ……………. .
Answer:
conduction, convection, radiation

Question 4.
During conduction, particles of the substance …………….. in their place.
Answer:
vibrate

Question 5.
In a convection current, warm air travels …………….. .
Answer:
upwards

Question 6.
A …………….. is necessary for the conduction of heat.
Answer:
medium

Question 7.
The ………………. of conduction of heat through a medium depends on the medium.
Answer:
speed

Question 8.
Convection takes place only in …………… medium.
Answer:
fluid

Question 9.
Transfer of heat in the absence of a medium is called ……………… .
Answer:
radiation

Question 10.
Substances through which heat travels easily and quickly are called …………… .
Answer:
good conductors

Question 11.
Substances through which heat travels very slowly are called ………… of heat.
Answer:
bad conductors

Question 12.
Copper is a better ………… of heat than …………. .
Answer:
conductor, iron

Question 13.
………………. made first thermos flask in 1892.
Answer:
Sir James Dewar

Question 14.
Neither conduction nor convection of the heat occurs in thermos flask due to the ……………… .
Answer:
vacuum.

Match the following:

Question 1.

Answer:

Question 2.

Answer:

Say whether true or false, correct and rewrite the false statements:

Question 1.
Glass is a bad conductor of heat.
Answer:
True

Question 2.
In a thermos flask, hot things remain hot and cold things become warm.
Answer:
False. In a thermos flask, hot things remain hot and cold things remain cold.

Question 3.
Radiation of heat depends upon the colours of the outer surface of the body.
Answer:
True

Question 4.
During radiation, the particles of the medium vibrate.
Answer:
True

Question 5.
Copper is better conductor of heat than iron.
Answer:
True

Question 6.
During conduction, particles of the conductor leave their original place.
Answer:
False. During conduction, particles of the conductor do not leave their original place, but only vibrate in their own place.

Question 7.
Hot water is heavier than cold water.
Answer:
False – Hot water is lighter than cold water.

Question 8.
A convection current always travels down wards.
Answer:
False – A convection current always travels upwards.

Question 9.
Every warm substance continuously emits heat in all directions around itself.
Answer:
True

Question 10.
Air is a bad conductor of heat.
Answer:
True

Define the following:

1. Conduction
2. convection
3. radiation
4. Transfer of heat.

Answer:

1. Conduction: The transfer of heat from one end of a solid substance to the other, without the particles leaving their original place is called conduction.
2. Convection: Transfer of heat in fluids due to formation of currents is called convection.
3. Radiation: Transfer of heat in all directions in the absence of a medium is called radiation.
4. Transfer of heat: The flow of heat from one place to another is called transfer of heat.

Give scientific reasons:

Question 1.
Cricketers wear white clothes when playing in the sun.
Answer:
White clothes do not absorb heat but reflect back therefore cricketers wear white clothes while playing in the sun.

Question 2.
Sawdust is a bad conductor of heat.
Answer:
Sawdust is a bad conductor of heat because heat travels very slowly through it.

Question 3.
We can feel the heat of table lamp under it.
Answer:
We can feel the heat of table lamp under it because every warm substance continuously emits heat in all directions around itself by radiation.

Question 4.
Medium is necessary for conduction.
Answer:
Conduction is the transfer of heat from one end of a substance to another. Transfer of heat has to be done by particles of a substance and particles of a substance are particles of a medium. Hence, a medium is necessary for conduction.

Question 5.
Explain the structure and functioning of thermometer containers-
Answer:

1. Thermoware containers keep food hot. These containers consist two boxes fitted one inside the other.
2. The outer box is made up of plastic while the inner one is made up of a shiny metal, there is air between the two boxes.
3. Air is a bad conductor of heat. Thus, heat is not lost by either conduction or convection. Also, the shiny inner surface prevents heat loss due to radiation.
4. The container has a plastic lid. This also prevents any transfer of heat.

Question 6.
what is mailed infrared camera? Write its uses.
Answer:

1. Radiation of heat takes place from many objects in nature such as trees, mountains, stones and roads.
2. A camera has been developed which uses these radiations to make our surroundings visible even at night. This is called infrared camera.
3. It is used to keep watch on the movements of the enemy during the night.
4. It is also used to track the movements of animals in the wild.

Question 7.
Why is mercury used in a thermometer?
Answer:
Mercury is used in a thermometer because of the following properties.

1. There is a big difference between the freezing point and boiling point of mercury. Its freezing point is – 39° C and its boiling point is 357° C.
2. It is shiny and can be easily seen.
3. It does not stick to glass.
4. It expands regularly and uniformly in all conditions.

Question 8.
Write the difference between Conduction, Convection and Radiation.
Answer:

Question 9.
Draw and explain about the Thermos flask or Dewar flask.
Answer:

Principle:
1. As there is no medium in the vacuum between the two bottles, no transfer of heat can take place by conduction or convection.
2. Radiant heat is reflected back inside from the shiny surfaces.
3. Glass and plastic are bad conductors of heat hence they do not transfer heat either into or out of the bottle. Thus transfer of heat does not take place by any of the three modes, namely conduction, convection or radiation Hence, hot things in the flask remain hot and cold things cold.

Structure:

1. A thermos flask consists of two thin glass bottles fitted one inside the other.
2. The inner surfaces of the bottles have a silver coating to shine like a mirror.
3. A vacuum is created in the space between the two bottles by removing all the air from it.
4. A plastic or cork lid is provided to fit on the mouth of the bottle.

Draw neat labelled diagrams of:

Question 1.
The relation between density and convection
Answer:

Question 2.
Conduction of heat
Answer:

Question 3.
Convection of heat
Answer:

Question 4.
Expansion and contraction of a liquid
Answer:

Question 5.
Thermos flask
Answer:

Can you tell?

Answer the following questions:

Question 1.
Why does the halwai wrap up cloth around the end of his slotted spoon while stirring the boiling milk in his large kadhai?
Answer:
The halwai wrap up cloth around the end of his slotted spoon while stirring the boiling milk in his large kadhai because (i) His slotted spoon is made up of metal and metal is a good conductor of heat so due to constant heating spoon gets very hot which makes hand to get burnt, (ii) But cloth is a bad conductor of heat so it does not allow heat to reach till hand and halwai does not feel hot when he stirs the boiling milk.

Question 2.
Why do we hold a steel glass in a handkerchief while drinking hot milk from it?
Answer:

1. Steel is metal and it is a good conductor of heat. So due to hot milk it becomes hot and it is difficult to hold. Person’s hand get burnt due to it.
2. So it is better to hold in a handkerchief because handkerchief is made up of cloth which is a bad conductor of heat. So your hand does not feel hot.

Use your brain power!

Question 1.
Why do we wear woollen clothes in winter?
Answer:
We wear woollen clothes in winter because

1. Air is a poor conductor of heat and woollen clothes do not allow the transfer of body heat.
2. Therefore we do not feel cold in woollen clothes and get protected from cold in winter.

Question 2.
Why do we use white clothes in summer and dark or black clothes in winter?
Answer:

1. White clothes do not absorb heat, so in summer, weather is very hot and white clothes protect us from heat whereas in winter it is very cold so we need more heat.
2. Dark or black clothes absorb more heat so we get protection from cold.

Question 3.
Why is there a gap at the joints of rails and of cement concrete bridges?
Answer:

1. The joints of rails and cement concrete bridges are made of iron. Metal is a good conductor of heat so in summer due to heat it expands and its length will be increased.
2. To allow for this expansion, gaps are kept.
3. If these gaps are not kept, then after expansion the rails and cement concrete would have buckled upwards due to lack of space.
4. Due to that bridges would crack and railway tracks get crooked.

Question 4.
Why is mercury or alcohol used in a thermometer?
Answer:
Mercury is used in a thermometer because of the following properties.
Alcohol is used in a thermometer for the following properties.

1. It can measure a low temperature because its freezing point is low. (-115°C) but it can not measure higher temperature as its boiling point is low.
2. It can measure the temperature precisely because it has large expansion coefficient.
3. It’s expansion is regular.
4. Less hazardous.

Question 5.
Why hot substance does not remain as hot after two or three hours?
Answer:
A little heat is lost from around the lid and by a small amount of conduction through the vessel. So hot substance does not remain as hot after two or three hours.

Diagram based questions.

Observe the diagram and answer the given questions below it.

1.

Question a.
What is the diagram about?
Answer:
The diagram is showing us the relation between density and convection.

Question b.
Why is the ice wrapped in wire gauze?
Answer:
Ice floats on water, to make it sink, it is wrapped in wire gauze.

Question c.
What does this experiment prove?
Answer:
When a liquid is heated, its density decreases and it rises upwards. This leads to the convection currents which makes the heated liquid rise upwards and cooler liquid takes it place.

2.

Question a.
What is the diagram about?
Answer:
Expansion and contraction of a solid substance.

Question b.
Does the same thing happen in liquids and gases?
Answer:
Yes. Generally substances solids, liquids and gases expand on heating and contract on cooling.

Question c.
Give one example of this property in everyday life.
Answer:
Gaps are present in between two railway line track joints so that they do not bend due to expansion.

3.

Question a.
Label parts 1 – 4
Answer:

1. Vacuum
2. metal/plastic jar
3. Spring
4. silvered surface of the glass.

Question b.
What is the principle of this object?
Answer:
As there is no medium in the vacuum between the two bottles, no transfer of heat takes place due to conduction and convection and radiated heat is reflected back by the shiny surface.

Question c.
State the uses of the given object.
Answer:
The temperature of substances inside it are maintained for some time. Hot things remain hot and cold things cold for 2 – 3 hours.

Question d.
What is an infrared camera?
Answer:
It is a camera which uses radiations to make our surroundings visible at night. Using this camera, it is possible to keep a watch on the movements of the enemy during the night.

Question e.
What is thermoware?
Answer:
Thermoware are object which do not allow heat to escape from them. So things stay warm in them. eg. hot pot, thermos flask.

Maharashtra State Board Class 7 Science Textbook Solutions

• The Living World: Adaptations and Classification Class 7 Science Textbook Solutions
• Plants: Structure and Function Class 7 Science Textbook Solutions
• Properties of Natural Resources Class 7 Science Textbook Solutions
• Nutrition in Living Organisms Class 7 Science Textbook Solutions
• Food Safety Class 7 Science Textbook Solutions
• Measurement of Physical Quantities Class 7 Science Textbook Solutions
• Motion, Force and Work Class 7 Science Textbook Solutions
• Static Electricity Class 7 Science Textbook Solutions
• Heat Class 7 Science Textbook Solutions
• Disaster Management Class 7 Science Textbook Solutions