Air and Its Constituents
Air and its Constituents-I
The atmosphere is a layer of air surrounding the earth. It extends up to three hundred and 320 km. Air is found in atmosphere as well as in dissolved in water. We cannot see air but we can feel the presence of air around us. Earlier air was considered as an element but now it has been proved that air is a mixture of gases. Antoine Lavoisier proved that nitrogen and oxygen are the main constituents of air with the help of an experiment. Components of air can be separated by simple physical methods. In Free State, nitrogen constitutes about seventy eight percent of the air. Nitrogen is colorless, odourless tasteless and non-poisonous gas. It is slightly lighter than air. Due to its inert nature nitrogen is used in food packaging to keep it fresh for a long time. Nitrogen is an important component of protein, which is essential for the growth and development of living beings. Certain bacteria present in the roots of leguminous plants like pulses and peas, convert atmospheric nitrogen or free nitrogen into soluble nitrates and other nitrogenous compounds that plants can readily absorb through their roots. Carbon dioxide constitutes about 0.03% to 0.04% of the air. The amount of carbon dioxide has gone up slightly because of human activities. Carbon dioxide is a colourless, odourless and tasteless gas. Carbon dioxide is non-combustible and non-supporter of combustion. Along with the gases certain amount of water vapours is always present in air which is also known as moisture. The presence of water vapour in the air is maintained by water cycle. Inert gases are also called rare gases or noble gases because they are highly stable and unreactive. They are helium, neon, argon, krypton, xenon and radon.
Air and its Constituents-II
Oxygen is vital for life. All human beings, plants and animals depend on oxygen to stay alive. When we breathe, we take in oxygen and breathe out carbon dioxide. Oxygen is also essential for combustion. Aquatic animals and plants use the dissolved oxygen present in water for their survival. Oxygen is the second major component of air and takes up 21% of the space. It supports life on the earth. Oxygen can be obtained by the thermal decomposition of some compounds containing oxygen like mercuric oxide, potassium nitrate, potassium chlorate, hydrogen peroxide etc. Oxygen can also be prepared by the electrolysis of water. Oxygen is a colourless, odorless and tasteless gas. It is slightly heavier than air. Metals and non-metals on burning in oxygen form their oxides and this reaction is called oxidation reaction. Oxidation is generally accompanied by evolution of heat and light. The wasting away of a metal layer after layer due to the formation of some compounds on its surface is called corrosion. Corrosion of iron is called rusting. Oxygen cylinders are provided to patients suffering from respiratory problems. Dust particles are tiny solid soil particles present in air.