How is oxygen useful to us?

Without oxygen there would have been no life on this earth. Without it no living being-trees, plants or animals-can survive. Hence it will not be a misnomer to call it a life-giver. Do you know what it is and why it is absolutely essential for us?

Oxygen is a gaseous element. This was first discovered by Lavoisier and Priestley. It is a colourless, tasteless and odourless gas. In the atmosphere the air contains 21% oxygen, 78% nitrogen and rest one percent other gases. In the earth's crust, it is found in the form of oxides of metals, the proportion being up to 50%. At - 185 degree centigrate under right pressure it can be liquefied. In the liquid state its colour becomes light blue. At - 219 degree centigrate, it can be converted into solid state.
In the laboratory, this is obtained by heating the mixture of potassium chlorate and manganese dioxide. From the atmosphere, it is obtained by the fractional distillation of air. The air is compressed to two hundred times the normal atmospheric pressure and passed through a narrow hole into a chamber. As the pressure is suddenly dropped, the air is liquefied and collected in the chamber. The nitrogen gas is separated from this by a special method and oxygen is left in the liquid state.
Oxygen is very useful to us in many ways. All the living beings use oxygen for breathing. Trees and plants take oxygen in the night for survival. By burning oxygen gas along with the acetylene gas, a high temperature flame is produced. This flame is used for welding and cutting metals. Oxygen is also used as a fuel in space vehicles.
When patients have breathing difficulties, oxygen is given to them to ease this trouble. It is also used for breathing purposes while climbing mountains or diving in the sea. This helps in the oxidation of food in our body which ultimately gives us energy. Our fuel burns due to oxygen and the aquatic animals survive with its help.
We cannot breathe in pure oxygen for long. Fresh air is essential for us because it contains more oxygen and breathing in fresh air makes us feel fresh and active. Thus, we should keep open the doors and windows of our rooms for fresh air. we should not cover our face while sleeping as this stops the fresh air from reaching in.
We feel suffocated in big crowds because the quantity of oxygen becomes less there. During winter, one should not sleep in a closed room by burning coal. The burning of coal converts the oxygen into carbon dioxide and carbon monoxide. Carbon monoxide is a poisonous gas and very injurious to health.