Welcome to our presentation

1. Welcome to our presentation

2. Air

3. Air • Air is all around us. We cannot see it. • We Cannot smell it. Air is everywhere – on the ground, on the tree-tops and high up in the sky where aeroplanes fly. • The air covers the earth like a blanket. This cover of air is called the atmosphere.

4. What is air Air is a mixture of gasses. The gasses nitrogen and oxygen are present in large amounts in the air. The other present in the atmosphere in small quantities are carbon dioxide, argon, and helium, ozone, and water- power.

5. Carbon dioxide • Carbon dioxide is another gas that is needed by plants to make their food. They change carbon dioxide into sugar with the help of water and sunlight. This process of making food in plants is called photosynthesis. This sugar is stored in different parts of the plant which we eat

6. Air pressure is very useful for us. • We make use of air –pressure in drinking cola with the help of a straw . As we suck the air, vacuum is Created inside the straw. This develops a low pressure inside the straw.

7. Air pressure is very useful for us. (Contd..) • We make use of air- pressure to fill up ink in a fountain pen. The ink filler drives out the air filled inside the pen. This results in a low pressure inside the pen. The air outside exerts pressure on the surface of the ink and forces it to enter the pen.

8. Air pressure is very useful for us. (Contd..) • This shows that air is needed for burning. • Oxygen is the gas in air which helps in burning.

9. Air pressure is very useful for us. (Contd..) • Doctors make use of air pressure to fill a syringe with medicine.

10. To remember • The cover of air around the earth is called the atmosphere. • Air is mixture of gases. • The most plentiful gases in air are nitrogen and oxygen.

11. Air is needed for burning Place a lighted candle on the table. Cover the candle with a glass tumbler. After some time, the candle stops burning. Why ?