General science notes class 8
Air is an invisible mixture of gases made up of a mass of millions of tiny gas molecules that moves randomlyandathigh speed. Without airthe earth would belifeless. Composition of the Atmosphere The atmosphere consists of a mixture of gases which are present in varying proportions. Its major constituents are nitrogen 78% and oxygen 21%. The rest of the gases 1% include carbon dioxide, helium, ozone, argon and hydrogen. Impurities like dust, smoke, salts, carbon monoxide and other chemicals are also present in the atmosphere. In its lower layer the atmosphere contains water vapour too. Nitrogen is the largest component and is essential for survivaland growthof plants. Oxygen is the second most plentiful gas. All living beings breathe in oxygen while the green plants breathe out oxygen. Green plants use carbon dioxide present in the atmosphere to make their food. Thus, the plants help in maintaining a balance between ...