• All living organisms on the Earth need air to survive.
• A thick blanket of air, called the atmosphere, surrounds our Earth.
• The Earth’s atmosphere has a portion that contains high levels of ozone gas.
• This layer, called the ozone layer, protects us from the harmful ultraviolet rays of the sun, thus preventing many eye problems and skin cancer in human beings.
• Air cannot be seen but it can be felt when it moves.
• Air, when moves, help light-weight things move. For example, the leaves of the trees rustling or clothes on the clothesline swaying.
• Moving air is called wind.Read More...
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...
BALANCE OF OXYGEN AND CARBON DIOXIDE IN THE AIR
• The balance of oxygen and carbon dioxide in the atmosphere is maintained through respiration in plants and animals and by photosynthesis in plants.
• Plants produce oxygen during photosynthesis and utilize oxygen during respiration.
• They produce much more oxygen during photosynthesis than they consume.
• This is how the oxygen consumed by plants and to a large extent by animals is replenished in the air through photosynthesis.Read More...
• Pollution is the addition of substances in the environment in quantities that are harmful to living beings.
• Air is getting polluted day by day because of various human activities.
• Burning of fuels such as coal and petroleum, excessive burning of fuels such as wood and coal, smoke and harmful gases released from industries, smoke released by vehicles, and machines releasing gases are the major causes of air pollution.
• These gases spread in the air and spoil the quality of air, thereby making it impure.
• Air pollution has major effects on plants, animals as well as human beings.
• Harmful gases present in polluted air make breathing difficult.Read More...