Important Questions for CBSE Class 7 Science Chapter 8 - Winds, storms and cyclones (Not in the Current Syllabus)

Very Short Answer Questions (1 Mark)

Indicate whether the following statements are true or false. If false, correct the statement.

1. Moving air is called a wave.

Ans: False. Moving air is called wind.

2. Only wind exerts pressure.

Ans: False. All matter exerts pressure including air.

3. Cyclones may form within tornadoes

Ans: False. Tornadoes may form within cyclones

4. Low wind speed is accompanied by higher pressure.

Ans: True.

5. Wind speed is measured using an ammeter.

Ans: False. Wind speed is measured by an anemometer.

6. Air moves from a region of lower air pressure to a region of higher air pressure.

Ans: False. Air moves from a region of higher air pressure to a region of lower air pressure.

7. Air expands on heating.

Ans: True.

8. Warm air is lighter than cold air.

Ans: True.

9. Sun heats all parts of the earth uniformly.

Ans: False. Sun heats different parts of the earth differently.

10. Winds that carry water are monsoon winds.

Ans: True.

Short Answer Questions (3 Marks)

11. Demonstrate that air exerts pressure.

Ans: A half-filled tin can of water is heated until the water boils. When the water begins to boil, it is covered tightly with a lid and placed under cold running water.

The can's shape becomes warped. The cold water condenses part of the steam that has built up inside the bottle. The amount of air within the bottle is reduced as a result. Because there is more air outside than inside, the air outside exerts more pressure than the air inside, causing the container to deform. This demonstrates that air exerts force.

12. Demonstrate that higher wind speeds are accompanied by lower pressure.

Ans: Fill two equal-sized balloons with water. Fill the balloons with air and tie them together with a string. Each balloon should be suspended from the opposite ends of a short stick. Inflate the balloons by blowing air between them. The balloons appear to be getting closer together. Blowing air between the balloons decreases the pressure as external pressure causes the balloons to close in on each other. This demonstrates that lower pressure is associated with faster wind speed.

13. Explain why warm air is lighter than cold air.

Ans: Air expands when it heats up. As a result, warm air takes up more space than cold air. Hence, warm air has a higher volume than cold air for the same amount of air. The warm air becomes lighter as the density of the airdrops.

14. Explain through a demonstration how hot air expands.

Ans: Take a boiling tube and wrap a balloon over its neck. In a beaker of boiling water, place the boiling tube. The balloon inflates slightly, as can be seen. When the same boiling tube is submerged in ice-cold water, the balloon deflates as expected. When a boiling tube is submerged in hot water, the air inside the tube warms up. As a result, the air expands and the balloon inflates. This demonstrates how heated air expands.

15. What is a cyclone watch?

Ans: A cyclone watch, also known as a cyclone alert, is a warning issued 48 hours ahead of the arrival of a cyclone. Satellite images and radar breakthroughs have made this possible. A cyclone warning is issued 24 hours before the arrival of a cyclone.

Long Answer Questions (5 marks)

16. Explain the formation of a cyclone.

Ans: A cyclone is a weather phenomenon that occurs when low pressure and high temperatures combine. It forms above the water and travels closer to the land. One section of the air becomes extremely hot and climbs rapidly. The low-pressure area is flooded with cold air from the surrounding regions. This results in hurricane-force winds. The warm air cools and condenses as it rises, forming water droplets and clouds. Heat is discharged into the environment during this process. This heat causes the air around it to heat up, even more, causing it to rise. The cycle is repeated until a low-pressure area occurs, which is encircled by high-speed winds rotating around it. A cyclone is a name given to this situation. The cyclone's eye is defined as a low-pressure area in the centre. Temperature, wind speed, air pressure, and humidity all play a role.

17. What are thunderstorms?

Ans: Thunderstorms are high-velocity rain-carrying winds that typically form in hot, humid environments. The rising winds are caused by the rising temperatures. Water droplets are carried upward by these breezes. The water droplets cool and freeze as they rise upwards, then fall back down. Lightning and thunder are caused by the rapid fall of water droplets combined with rising air. This is what is referred to as a thunderstorm. Thunderstorms can become cyclones when temperatures are extremely high and air pressures are extremely low.

18. Explain the structure of a cyclone.

Ans: The eye of the cyclone is a quiet area in the centre of the storm. A cyclone is a fiercely revolving mass of air that reaches a height of 10-15 kilometers. The eye's diameter can range from 10 to 30 kilometres. There are no winds or clouds in this area. A region of wetlands surrounds this place. For roughly 150 kilometres, there are clouds. High-speed winds (150-250 km/h) and heavy clouds characterise this location with a lot of rain. The wind speed progressively lessens as you go away from this area.