AP State Syllabus AP Board 7th Class Science Important Questions Chapter 8 Air, Winds and Cyclones

## AP State Syllabus 7th Class Science Important Questions 8th Lesson Air, Winds and Cyclones

### 7th Class Science 8th Lesson Air, Winds and Cyclones Important Questions and Answers

Question 1.
How do you prove that air exerts pressure?

1. We know that a bicycle tube or tube of any other vehicle can burst when it is over filled with air.
2. Take a balloon and fill it with air. Keep blowing more and more air into it.
3. The balloon expands and after a point bursts.
4. The reason for the burst is the increase in air pressure inside them.
5. For example a balloon being filled with air, the air filled football that becomes hard, water rising through a hand pump, the tubes of cycle, scooter or car are all due to the pressure exerted by air.

Question 2.
How do you show that air exerts pressure by a simple experiment?

1. Take a syringe and draw out its plunger (piston) to the limit.
2. Close the nozzle of the syringe with a finger and press the piston.
3. The finger experiences the pressure exerted by air.

Question 3.
What happens on heating air? How is pressure related to this?

1. It is important to remember that on heating the air expands and occupies more space.
2. When something occupies more space, it becomes less dense.
3. The warm air is therefore less dense than cold air. Thus smoke and hot air go up.
4. Similar to observations of activities done so far, numerous factors contribute to heat air.
5. When the air rises up, air pressure at the place becomes low and we have many kinds of winds as air comes into occupying areas of lower pressure.
6. The differential heating of land and water by the sun leads to land and sea breeze.

Question 4.
How are land breeze and sea breeze developed?

1. The land heats up faster than the sea, so warm air rises over the land during the day as it is warmed by the Sun.
2. At certain times of a year, this can create a sea breeze which is a gentle breeze blowing into the land.
3. At night, the land cools faster than the sea, reversing the air flow.
4. This creates a land breeze that blows out to sea.

Question 5.
How are we getting monsoon winds? In which months do they come?

1. We have read about the sea breeze and the land breezes.
2. In summer, near the equator the land heats up faster and during the day the temperature of the land is higher than the water in the ocean.
3. The air over the land gets heated and rises.
4. This causes the winds to flow from the oceans towards the land.
5. These are monsoon winds.
6. This is usual during the months of June to September.

Question 6.
How are winds useful in our life?

1. The direction of the wind flow gets usually reversed in the months from December to early March.
2. The wind flows from the land to ocean as the sea cools more slowly.
3. The winds from the oceans carry water and bring rains.
4. Farmers in our country depend mainly on rains for their harvests.
5. We can also generate energy from high-speed wind.
6. Thus we can see the usefulness of winds in our life.

Question 7.
Describe how cyclones are formed.

1. Tropical cyclones are like giant engines that use warm moist air as fuel.
2. The warm moist air rises upward from near the surface.
3. The warm air rises causing an area of lower air pressure below.
4. Air from surrounding areas of high air pressure pushes into the low pressure area.
5. Then this “new” air becomes warm and rises too.
6. As the warm air continues to rise, the surrounding air swirls – into take its place and the water from the sea surface also comes up with the air.
7. As the warmed moist air rises and cools off, the water in the air forms clouds.
8. The whole system of clouds and winds spins and grows, fed by the ocean’s heat and water evaporating from the surface. See the figure.
9. These kinds of satellite images help us to predict the path of the cyclones to some extent.

Question 8.
Write the Do’s and Don ‘ts during cyclones.
Cyclones – Do’s and Don’ts:

1. We should not ignore the warnings issued by the meteorological department through T.V., Radio or newspapers: Pass on the information to others and ignore rumors.
3. We should make necessary arrangements to shift essential household goods, domestic animals and vehicles, etc. to safer places.
4. Switch off electrical mains in your house.
5. Keep ready the phone numbers of all emergency services like police, fire brigade, and medical centres.
6. Pack essentials for yourself and your family to last few days, including medicines, special food for those who would need it. This may include babies and elders.

Question 9.
Write the precautions to be taken before the cyclone.
Precautions to be taken before a cyclone:

1. We should be cautious about rumours.
2. If we feel that houses are not safe at the time of cyclone, we have move into a pucca building in the vicinity.
3. We should keep mobile phones in a waterproof bag, fully charged. If we have more than one mobile phone, we have to use one phone at a time, leaving the other phones switched off and using them one after the other to ensure communication to the longest possible period.
4. If we have to vacate the house close the toilet seat with sandbags.
5. We should close the drainage holes to prevent reverse flow of sewage.
6. The trained students should cooperate with the response teams.
7. We should make necessary arrangements to shift essential household goods, domestic animals and vehicles, etc. to safer places.

Question 10.
What are the post-cyclone measures?
Post cyclone measures :
If you are staying in a cyclone hit area-

1. Strictly avoid any loose and dangling wires.
2. Do not drink water that could be contaminated. Always store drinking water for emergencies.
3. Whenever there is an outbreak of dysentery, we should take tea, decoction and starch solution (Ganji).
4. We should not go near to bunds of tanks, streams, the river banks, fallen trees, buildings, poles and seashores to play or sight-seeing and taking selfies.
6. At the time of cyclones, some people lose their beloved family members and children or pets. In such situations, we should give assurance, guidance and counselling in order not to go to a depressed state.

Question 11.
Establish the fact that moving air creates low pressure.

1. Take a glass and a postcard.
2. Keep the glass on a table and the postcard on the glass.
3. Wave our hand or note book above the postcard to displace the air just above the postcard.
4. As the card moves, it moves the air there creating low pressure.
5. Due to this low pressure the card on the glass rises up.
6. It means moving air creates low pressure.

Question 12.
What are the reasons that different areas have different temperatures? How does this help in getting rain?

1. Uneven heating takes place on the surface of the earth.
2. We know that regions close to the equator gets more heat from the sun.
3. This is because of the direction of the sunlight being straighter close to the equator.
4. The air in these regions gets warmer.
5. The warm air rises, and the cooler air from the regions in the 0 – 30° latitude belt on either side of the equator moves in.
6. This movement of air sets forth winds that move over the earth.
7. We have also seen that the increased wind speed is accompanied by a reduced air pressure and this aids rains.

Question 13.
Do winds cause harm? Explain.

1. We are familiar with the word cyclone.
2. During the months of May – June or October – November reports about them can be seen in the Newspapers and TV.
3. This way winds cause harm.

Question 14.
Where do we And air? Explain it with an activity.

1. Take a bucket full of water and transparent glass.
2. Take a paper, crumple it into a ball and push it to the bottom of the glass.
3. Invert this glass and immerse it into the bucket of water. Keep the glass straight and press it so that the glass is completely under water.
4. Take it out and observe what happens.
5. The paper in the glass did not wet.
6. However if the glass is tilted air in the glass escapes as bubbles through water and water enters the glass.

Question 15.
Describe a simple activity to show the presence of air.

1. Fill a bucket with water.
2. Take a bottle with a narrow mouth and immerse it in the bucket till it fills with water.
3. During the time the bottle is filling with water bubbles of air come out of the glass.
4. This air is earlier filled in the glass. So the glass is not empty but full of air.
5. Any bottle, glass or any other container that appears empty is actually full of air.
6. Nothing can be added to it unless the air inside is removed.
7. It is only when some air is removed that something else can enter.
8. Air occupies the space around us.

Question 16.
Show by a simple experiment that air expands on heating.

1. Take an empty injection bottle and one empty ball point refill.
2. Remove the pin of the refill and insert one of its ends in the cork of the injection bottle as shown in Fig.
3. Put a water drop on the upper end of the refill.
4. Rub your hands together so that they become warm.
5. Carefully pick up the bottle and hold it in both your hands for sometime.
6. So that the bottle also becomes warm.
7. The water drop inflate in the refill.
8. This is because air in the bottle expands due to the heat supplied by the hands.

Question 17.
‘Hot air is lighter than cold air’. How do you prove it?

1. Take two paper bags or empty paper cups of the same size.
2. Take a broomstick. Hang the two bags in the inverted position on the two ends of the broomstick.
3. Tie a piece of thread in the middle of the stick. Hold the stick by the thread, like a weighing balance.
4. Put a burning candle below one of the bags as shown in the figure (b) and observe what happens.
5. Note that we have used paper bags or cups as they are of a light weight and it would be easier to see the results of this experiment if we take any such light objects to hang on the thread.
6. The balance of the bags is disturbed.
7. This proves that hot air is lighter than cold air.

Question 18.
‘Air moves from a region of higher pressure to a lower pressure’. Prove this statement by a simple experiment.

1. Take a balloon. Blow air into it. As we fill it up, it expands and it becomes harder to press the walls of the balloon. The inside air exerts pressure on the walls of the balloon.
2. Open the mouth of the balloon slightly. Air from the balloon comes out.
3. We can open the mouth less or more and control the flow of air.
4. The air in the balloon is at high pressure and it goes towards low pressure area.
5. We already know that when air moves, it is called wind. Air moves from the region where the air pressure is high to the region where the pressure is low.

Question 19.
How can you demonstrate that warm air rises up?

1. Take an incense stick (agarbati) and light it. Observe the smoke of the incense stick.
2. When something occupies more space, it becomes less dense. The warm air is therefore less dense than cold air.
3. The smoke rises up indicating that warm air rises up.

Question 20.
Write an activity to prove that moving air creates low pressure.

1. Wet the edges of glass and put a postcard on it, and hold it inverted with our left hand as shown in figure and move your right hand or note book to move the air form under the paper.
2. Due to the movement of the hand or note book, air there moves fast.
3. This moving air creates low pressure and the postcard is pushed out by the air inside the glass.

Question 21.
Prove by an activity that increased wind speed is accompanied by a reduced pressure.

1. Take a glass containing water and two straws. Keep one straw in the water and another in horizontal direction as shown in figure and blow through the horizontal straw.
2. When you blow over the straw the water comes out due to low pressure which forms inside the straw.
3. So the water from the glass reaches up in the straw due to high pressure.
4. We see that the increased wind speed is accompanied by a reduced air pressure.

Question 22.
What is a cyclone? What are the other names for it?

1. Cyclones are a form of violent storms on earth.
2. People call these storms by names such as typhoons, hurricanes, etc. depending on where they occur.

Question 23.
What factors contribute to cyclone? When and where do they likely to occur?

1. Factors like wind speed, wind direction, temperature and humidity contribute to the development of cyclones.
2. In India cyclones usually occur in the month of May – June and October – November.
3. More cyclones tend to occur on the eastern side i.e. towards Bay of Bengal.

Question 24.
What are the effects of cyclone? On what factors the destruction of a cyclone depends?

1. Cyclones can be very destructive.
2. The main effects of cyclones include heavy rain and strong wind.
3. The destruction of a cyclone depends mainly on its intensity, its size and its location.

Question 25.
What are the steps needed to use a dropper? Explain its functioning.

Fig. (a): The air present in the tube of the dropper is removed by pressing the rubber head.
Fig. (b): Putting the open end of the tube of the dropper in water and releasing the pressed rubber head.
Due to low pressure in the tube water enters into it.
Fig. (c): Rubber head is made free from pressing. Water entered in to the tube of the dropper as air there was already sent out.

Question 26.
What is wind?

1. The air around us is rarely still. It moves continuously from one direction to another.
2. The movement is in many directions.
3. This is what we call winds.
4. So we know that wind is moving air.

Question 27.
What are the advantages of advanced technology with regard to cyclones? How do you appreciate it?

1. Advanced Technology has helped and these days we are better protected.
2. In the early part of last century, coastal residents may have had less than a day to prepare or evacuate their homes from an oncoming cyclone.
3. The world today is very different.
4. 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 hours in advance.
5. The message is broadcast every hour or half an hour when a cyclone is near the coast.
6. Information about cyclones will be given by the Indian Meteorological Department (IMD).

Question 28.
What are the post cyclone measures we have to take?
Post cyclone measures: If you are staying in a cyclone hit area

• Strictly avoid any loose and dangling wires.
• Do not drink water that could be contaminated. Always store drinking water for emergencies.
• Do not go out for the sake of fun.

Question 29.
Observe the experiment and answer the following questions.

1. What happens to the water drop in the refill?
2. Why is the position of water drop changed?

1. The water drop inflates in the refill.
2. Because we know that air expands on heating. So. the water drop is moved upwards. Hence, there is a change in the position of the water drop.

Question 30.
Observe the experiment and answer the following question. When two identical, inverted paper bags are hung on a balance, they balance each other as shown in right figure.

i) After a burning candle is placed under one of the bags as shown in the left figure, why is the balance of the bags disturbed?