Air Around Us Notes

INTRODUCTION

COMPOSITION OF AIR

•           Until the eighteenth century, people thought that air was just one substance.

•           But experiments have proved that air is a mixture of several gases.

•           Air contains mainly nitrogen, oxygen, and remaining includes carbon dioxide, noble gases, water vapour, dust particles, and traces of other gases.

Nitrogen and Oxygen:

•           Air contains about 78% nitrogen and 21% oxygen.

•           Oxygen in air supports burning whereas nitrogen does not.

78% nitrogen, 21% oxygen, 1% other gases

AIR SUPPORTS LIFE

•           We all need air to survive.

•           Air contains oxygen and carbon dioxide useful to plants and animals.

•           Plants use carbon dioxide of the air to make their own food by a process called photosynthesis.

Points to Remember:

•           Breathing is a physical act of taking in oxygen and giving out carbon dioxide.

•           Respiration is a chemical process by which glucose in the body breaks down to give energy.

In Plants:

•           Plants have tiny pores called stomata, found on the underside of a leaf.