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