Here are extra questions from the chapter Wind, Storm and Cyclones of class 7 NCERT science.

1. What is wind?

Wind is moving air.

2. Why does a tin can with hot water gets distorted when water is poured on it?

When water is poured on the tin can containing hot water, some of the steam inside the can condenses into water. This reduces the amount of air inside. As pressure of the air inside the can is now lower than the pressure exerted by the air outside the can, the can gets compressed.

3. Why is it hard to force a paper ball into a bottle by blowing into the bottle?

When we blow into the mouth of a bottle, the air near the mouth has higher speed. This decreases the pressure there. The air pressure inside the bottle is higher than near the mouth. Consequently, the air inside the bottle pushes the ball out.

4. Increased wind speed is accompanied by reduced …………………………….

air pressure

5. Air moves from the region where air pressure is ……………………… to the region where air pressure is …………………………

high to low

6. Air expands on heating. Prove with an experiment.

Take a boiling tube. Cover its opening tightly with a balloon. Take some boiling water in a beaker and put the boiling tube in the beaker. If we observe the tube and balloon for 2-3 minutes, we can see that the balloon becomes inflated. When the boiling tube was put in the hot water, it caused the air inside the tube to become warm. As heat expands air, the balloon becomes inflated. This experiment proves that air expands on heating.

7. Explain why smoke always rises up?

Smoke is warm air and warm air always moves up.

8. Why is warm air lighter than cold air?

When air is warm it expands and occupies more space. When the same thing occupies more space, it becomes lighter. By contrast, cold air occupies less space and hence it is heavier.

9. What causes winds?

Unequal heating between the equator and the poles causes the cold air from the north and south poles to move towards the equator where the air is warm. As warm air near the equator moves up, cold air from the colder regions rush in to take up that space. This flow of air causes winds.

10. What are monsoon winds?

In summer, near the equator the land warms up faster than ocean water. In fact, most of the time land is warmer than the oceans. As a result, air over the land become hot and rises up. This causes winds to flow from the oceans towards the land. These are the monsoon winds.

11. What are thunderstorms?

Thunderstorms are common in hot, humid, tropical regions. The hot weather in tropical regions causes strong upward rising winds. As these winds go upwards, they carry water droplets with them. At an altitude these water droplets freeze and fall down. The swift movement of the falling water droplets along with rising air create thunder and lightning. This is what we call a thunderstorm.

12. What is the eye of a cyclone?

The eye of a cyclone is its centre which is a calm area.

13. What is a cyclone?

Before clouds are formed, water takes up heat from the atmosphere to change into vapour. When this water vapour changes to its liquid state as raindrops, this heat is released to the atmosphere. As a result, the air around warms up and tends to move up. This causes a drop in air pressure and more air rushes to the centre of the storm. This cycle is repeated and ends in the formation of very low-pressure system with highspeed winds revolving around it. This is what we call a cyclone.

14. A cyclone is called a …………………………. in the American continent.

hurricane

15. In Philippines and Japan, a cyclone is called a ………………………….

typhoon

16. What is a tornado?

A tornado is a dark funnel shaped cloud that reaches from the sky to the ground.

17. Which part of India is the most vulnerable to cyclones?

East coast

18. Which instrument is used to measure wind speed?

Anemometer

19. All storms are essentially …………………………..

low pressure systems

Class 7 Science Solutions

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