Stabroek News Sunday

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## Hello Boys and Girls,

Are you doing well? Have you been doing lots of revision in your spare time? Are you preparing well for your NGSA Mock Exam. #2? Have you been focusing on your school work? Have you been thinking carefully about the exercises you are doing? Have lots of fun as you work.

For the past few weeks we found out a lot about air. Do you remember them? Call a friend and together find out how much you know about air so far.

Look below to refresh your memory.

What is air really composed of?

Yes, air is a mixture of several invisible gases. Let us imagine that the air is made up of 100 small cubes (a). 21 of these cubes would be oxygen – 21% or 1/5. Most of the air is nitrogen, 78 cubes – 78% (b).

Other gases make up the other 1 part – 1%. In the 1% can be found carbon dioxide and other rare gases, such as argon and neon.

Another way of showing the different gases is by cutting up a circle to show the amounts (c). Because this is like cutting a pie it is called a pie chart.

This week we will conclude our investigat­ion of air. We have already seen that air is all around us. There is a layer around the earth . Can you tell what that layer is called? Yes, it is the atmosphere. The atmosphere protects the Earth from harmful rays from space and from the Sun. The atmosphere is like a blanket, which stops the Earth from getting too hot or too cold.

The atmosphere presses down on the Earth. As we learnt last week, this pressing force is called air pressure. If we travel upwards through the atmosphere there is less air above us and so air pressure becomes less as we go higher. Human Beings cannot survive if the air pressure is very low. Why is this so? Find out. What happens when we fly in aeroplanes? Aeroplanes have special cabins that keep the air pressure the same as on the ground. Exciting, isn’t it? Have you ever flown in an aeroplane and felt your ears uncomforta­ble? Why does this happen?

Can air become unhealthy?

Like water, air can also sometimes be made dirty and unsafe by pollution. (Do you remember this word being used when we looked at water?) Some gases and particles in the air can make it harmful for Human Beings, other animals and plants. Air pollution can come from many places. What are some of these places? Yes, some of the common places are :

• fumes from cars

• chemicals and smoke from factories • smoke from burning rubbish

• smoke from burning coal

• smoke from cigarettes

if people breathe in badly polluted air it can cause diseases. cancer are common diseases caused by air pollution.

## Fill in the blanks

i.) Plants absorb ____ to make their own food. iii.) Combustion cannot take place without ____ gas. iv.) ____ gas maintains the temperatur­e of the earth. v.) Carbon dioxide is ____ than air.

State True or False i.) Plants use oxygen during photosynth­esis. ii.) The only elements in the air are nitrogen and oxygen. iii.) Water vapour is present in the air. iv.) Air exerts pressure. v.) The compositio­n of air is constant in the atmosphere.

Match the following

## Column A

a.) Respiratio­n b.) Air c.) Photosynth­esis d.) Nitrogen e.) Wind

Column B ii.) It is moving air. iv.) It is a gaseous mixture

Asthma and lung

It is important that we keep our air as clean as possible so that it is safe for living things to breathe.

Here are some more simple exercises for you. These will help you in your revision. ii.) Oxygen is returned to the atmosphere by the process of ____. i.) Process of preparing food by plants. iii.) Process of burning food to get energy. v.) The major component of air.