Class 7 Science Chapter 8 Important Questions

Class 7 Science Chapter 8 Important Questions Answers and Main Keywords of Winds, Storms and Cyclones updated for academic session 2020-2021. Class 7 Science Chapter 8 extra questions are helpful for not only unit test but the periodic exams also.

We have covered all the topics from NCERT Textbooks and some other books also. These important extra questions of chapter 8 class vii science provides a perfect preparation of exams.

Class 7 Science Chapter 8 Important Questions 2020-2021

Class: 7Science
Chapter: 8Winds, Storms and Cyclones
Contents:Important Extra Questions with Answers

Class 7 Science Chapter 8 Important Questions Set – 1

Write down the destructive effects happened in Odisha in the year of 1999.

Orissa was hit by a cyclone with wind speed of 200 km/h on 18 October 1999. The cyclone smashed 45,000 houses making 7,00,000 people homeless. On 29 October the same year, a second cyclone with wind speed of 260 km/h hit Orissa again. It was accompanied by water waves about 9 m high. Thousands of people lost their lives. Property worth crores of rupees was destroyed. The cyclone affected agriculture, transport, communication, and electricity supply.

What are cyclones? How are they formed? Why are they so destructive?

Cyclones are the system of winds rotating inwards to an area of low pressure with an anti-clockwise or clockwise circulation. Cyclones develop from the large-scale clusters of thunderstorm cells that are often witnessed over tropical oceans. They get their energy from the evaporation of surface water with a temperature of more than 27 degree Celsius.
Tropical Cyclones are dangerous because they produce destructive winds, heavy rainfall with flooding and damaging storm surges that can cause inundation of low-lying coastal areas.

How can cyclones be predicted?

Meteorologists around the world use modern technology such as satellites, weather radars and computers etc. to track tropical cyclones as they develop.

    • How would you prove that high speed winds reduce air pressure? Explain with an activity.
      Crumple a small piece of paper into a ball of size smaller than the mouth of an empty bottle. Hold the empty bottle on its side and place the paper ball just inside its mouth. Now try to blow on the ball to force it into the bottle. It is difficult to force the paper ball into the bottle.
      When we blow into the mouth of the 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. The air inside the bottle pushes the ball out. This activity shows that high speed winds reduce air pressure.
    • What would happen if high-speed winds blew over the tin or thatched roofs of any houses?
      As we know that when air is blown over a strip of paper, then the strip of paper is lifted up. If high speed winds blow over the roofs of houses, they will reduce the air pressure above the roof. And if the roof of houses are weak, then higher air pressure from below will lift up the roofs which can then be blown away by the fast winds. Thus, weak room of houses (like the tin roofs or thatched roots) can be lifted and blown away by high-speed winds during a wind storm.

Class 7 Science Chapter 8 Important Questions Set – 2

Explain the temperature is also involved in the increasing or decreasing speed of wind.

Take a boiling tube. Stretch a balloon tightly over the neck of the tube. Pour some hot water in a beaker. Insert the boiling tube with the balloon in the hot water. Observed for any change in shape of balloon. We see that balloon lifts upwards. Take the tube out, let it cool down to the room temperature. Take some ice-cold water in another beaker and place the boiling tube in it. The balloon inflates when the boiling tube is placed in hot water. But the same balloon deflates when the tube is kept in cold water. This activity shows that warm air rises up and warm air is lighter than the cold air. In this way, we can say that difference in temperature is also involved in making speed of wind.

Explain how uneven heating between equator and the poles generates wind current.

The region closer to equator get maximum heat from the sun. This makes the air warm which rises up and the air from the regions in the 0-30 degrees latitude belt on either side of the equator moves in. These winds blow from the north and the south towards the equator. At the poles, the air is colder than that at latitude about 60 degree. The warm air at these latitudes rises up and the cold wind from the poles rushes in. In this way, wind circulation is set up from poles to the warmer latitudes.

Describe how uneven heating of land and water carry lots of water as monsoon winds.

In summer, near the equator the land warms up faster and most of the time the temperature of the land is higher than that of water in the oceans. The air over the land gets heated and rises. This causes the winds to flow from the oceans towards the land. These are monsoon winds.
In winter, the direction of the wind flow gets reversed; it flows from the land to the ocean. The winds from the oceans carry water and bring rain. It is a part of the water cycle. The monsoon winds carry water and it rains. Clouds bring rain and give us happiness. Farmers in our country depend mainly on rains for their harvests.

    1. What do you know about thunderstorm?
      Thunderstorms develop in hot, humid tropical areas like India very frequently. The rising temperatures produce strong upward rising winds. These winds carry water droplets upwards, where they freeze, and fall down again. The swift movement of the falling water droplets along with the rising air create lightning and sound. It is this event that we call a thunderstorm.
    2. Discuss how a thunderstorm becomes a cyclone.
      We know that water requires heat when it changes from liquid to vapour state. Before cloud formation, water takes up heat from the atmosphere to change into vapour. When water vapour changes back to liquid form as raindrops, this heat is released to the atmosphere. The heat released to the atmosphere warms the air around. The air tends to rise and causes a drop in pressure. More air rushes to the centre of the storm. This cycle is repeated. The chain of events ends with the formation of a very low-pressure system with very high-speed winds revolving around it. It is this weather condition that we call a cyclone.

Class 7 Science Chapter 8 Important Questions Set – 3

Write down the factors which contribute to the development of cyclones.

Factors like wind speed, wind direction, temperature and humidity contribute to the development of cyclones.

Write down the different names of cyclones around the world.

A cyclone is known by different names in different parts of the world. It is called a “hurricane” in the American continent. In Philippines and Japan, it is called a “typhoon”.

Explain how cyclones can cause tremendous loss of life and property.

Cyclones can be very destructive. Strong winds push water towards the shore even if the storm is hundreds of kilometres away. These are the first indications of an approaching cyclone. The water waves produced by the wind are so powerful that a person cannot overcome them.
The low pressure in the eye lifts water surface in the centre. The rising water may be as high as 3–12 metres. It appears like a water-wall moving towards the shore. As a result, the seawater enters the low-lying coastal areas, causing severe loss of life and property. It also reduces the fertility of the soil. Continuous heavy rainfall may further worsen the flood situation. High-speed winds accompanying a cyclone can damage houses, telephones and other communication systems, trees, etc., causing tremendous loss of life and property.

Write down the precautions to be taken during a thunderstorm.
A thunderstorm is always accompanied by a lightning. Lightning is a giant electric spark. When lightning strikes the earth, it can kill people. It also damages building. We should take the following precautions during a thunderstorm to protect ourselves from lightning:

    • i) Do not take shelter under an isolated tree. If you are in a forest take shelter under a small tree. Do not lie on the ground.
    • ii) Do not take shelter under an umbrella with a metallic end.
    • iii) Do not sit near a window. Open garages, storage sheds, metal sheds are not safe places to take shelter.
    • iv) A car or a bus is a safe place to take shelter.
    • v) If you are in water, get out and go inside a building.

Why do chimneys made of steel not require protection from lightning.
Steel is a good conductor of electricity. Due to this reason, steel chimneys do not require lightning conductor. They themselves pass the charge to the earth.

Class 7 Science Chapter 8 Important Questions Set – 4

What is an anemometer?

The device which is used to measure the wind speed is called anemometer. Since wind speed plays an important role in the formation of storms an anemometer becomes useful to predict the cyclones or storms in cyclone prone areas.

Describe a tornado.

Tornado is a dark funnel shaped cloud that reaches from the sky to the ground. The diameter of a tornado can be small as a metre and as large as a kilometre or even wider. The funnel of a tornado sucks dust, debris and everything that comes near its base (due to low pressure) and throws them out up to the top.

What is a lightning conductor? Why is it fixed on the top of high-rise building?

A lighting conductor is a long, flat, thick strip of copper with sharp point or spikes. The lower end of it is connected to copper plate deep into the earth.
It is fixed on the top of the building because the thundering electricity comes in its contact first and the building will not be damaged.

Discuss the structure of a cyclone.
A cyclone is formed in the atmosphere over warm sea water near the equator during the hottest summer months. As we know that wind speed, wind direction, temperature and humidity contribute to the development of cyclones. Generally, the centre of a cyclone is a calm area. It is called the eye of the storm. A large cyclone is a violently rotating mass of air in the atmosphere, 10 to 15 km high. The diameter of the eye varies from 10 to 30 km. It is a region free of clouds and has light winds. Around this calm and clear eye, there is a cloud region of about 150 km in size. In this region there are high-speed winds (150–250 km/h) and thick clouds with heavy rain. Away from this region the wind speed gradually decreases.

What precautions would you take, if you are staying in a cyclone hit area?
Some precautions, if we are staying in a cyclone hit area:

    • i) Do not drink water that could be contaminated. Always store drinking water for emergencies.
    • ii) Do not touch wet switches and fallen power lines.
    • iii) Do not go out just for the sake of fun.
    • iv) Do not pressurise the rescue force by making undue demands.
    • v) Co-operate and help your neighbours and friends.

Class 7 Science Chapter 8 Important Questions Set – 5

A flat in Mumbai with a balcony facing the sea has some clothes hung on a clothes line in the balcony. Towards which direction, the clothes will be blown in the afternoon? Explain it.

In the afternoon, the land gets heated faster than the water. The air over the land becomes hotter and rises up, creating a drop in pressure. This causes the wind to flow from the sea towards the land.
Thus, the clothes will be blown towards the house because of sea breeze flowing towards the land.

What do you mean by storm, lightning and thunder?

Storm: A period of violent weather with strong winds, and usually rain or snow is called a storm. A storm is the distributed state of the earth’s atmosphere which affects the surface of earth and all the objects on it.
Lightning: A natural flow of high voltage electricity within the cloud or between the cloud or cloud to the earth which appears as a bright flash of light in the sky, is called lightning. A cloud becomes electrically charged and produce lightning; its temperature must be close to the freezing point to water (which is 0 degree Celsius). Lighting is usually accompanied by thunder.
Thunder: The loud sound which is heard a little after a lightning flash is seen in the sky is called thunder. Thunder is produced by lightning as the high voltage electric spark of lightning heats the air in the atmosphere to a very high temperature. This extreme heating causes the air to expand at an “explosive rate” producing a loud sound called “thunder”. Thus, it is lightning which cause thunder. Lightning and thunder are the two characteristic features of a thunderstorm.

How does advanced technologies help people to be protected from cyclone?

These days we are better protected. In the early part of the last century, coastal residents may have had less than a day to prepare or evacuate their homes from an oncoming cyclone. The world today is very different. Thanks to satellites and radars, a Cyclone alert or Cyclone watch is issued 48 hours in advance of any expected storm and a Cyclone warning is issued 24 hrs in advance. The message is broadcast every hour or half hour when a cyclone is nearer the coast. Several national and international organisations cooperate to monitor the cyclone-related disasters.

Write a short note on the “Disaster Management” in case of cyclones.
The disaster management of a cyclone involves:

    • (A) Effective Safety Measures:
      i) A cyclone forecast and warning service.
      ii) Rapid communication of warning to the government agencies, the ports, fishermen, ships and to the general public.
      iii) Construction of cyclone shelters in the cyclone prone areas and administrative arrangements for moving people fast to safer places.
    • (B) Action on the part of the people:
      i) We should not ignore the warning issued by the metrological department through media like TV, radio or newspapers.
      ii) We should make necessary arrangements to shift the essential household goods, domestic animals and vehicles etc to safer places.
      iii) We should avoid driving on roads through standing water, as floods we have damaged the roads.
      iv) We should keep ready the phone numbers of all emergency services like police, fire brigade and medical centre.
    • (C) Some other precautions, if you are staying in the cyclone prone area:
      i) Do not drink water that could be contaminated. Always store drinking water for emergencies.
      ii) Do not touch wet electric switches and fallen power lines.
      iii) Do not pressurize the rescue force by making undue demands.

A flag mounted on a flag post near the sea coast flutters in the direction of sea. At what time of the day does this happen – at midnight or in the afternoon?
At night, the water cools down more slowly than the land. So, at midnight, cool wind from the land moves towards the sea. Therefore, at midnight the flag mounted on a flag post near the sea coast flutters in the direction of sea.