COMPOSITION OF AIR

COMPOSITION OF AIR:

Air cannot be seen, touched, or tasted, but it can be felt. It is much more than nothing. It is a mixture of various gases. Four-fifths of the air is nitrogen gas and one-fifth of it is oxygen gas. Another important component of air is carbon dioxide. We need oxygen to live, and plants need carbon dioxide to live.

         By volume, air contains 78.09% nitrogen, 20.95%  oxygen, 0.04% carbon dioxide, 0.93% argon, and small amounts of other gases.

ATOM:

The term 'atom' comes from the Greek word 'Atomos', meaning 'invisible'. Earlier, it was considered that atoms were the smallest unit of a substance and could not be split further. Today, we know that atoms can be further divided into minute particles. An atom is made up of the atomic nucleus, which consists of positively charged protons and an equal number of neutrons, and atomic shells. These are occupied by negatively charged electrons, which at high speed around the atomic nucleus-like planets around the sun.

ELEMENT:

An element is a 'pure substance' consisting of atoms of the same kind. Elements cannot be broken down into simpler substances, but they can be combined with other elements to make a new substance. Each element has a unique symbol, for example, 'O' means oxygen, 'Na means sodium, and Cl means chlorine. The number of protons in the atomic nucleus determines the element. This number is called the atomic number of the element.

MOLECULE:

A molecule consists of two or more than two atoms, which are held together by chemical bonds. A water molecule is made up of two atoms of hydrogen (H) and one atom of oxygen (O). Thus, the chemical formula of water is H2O. Elements also frequently occur in molecular forms. For example, two atoms of chlorine, oxygen, and nitrogen combine  to form Cl2, O2, and N2 respectively. They are complicated molecules as well, such as those of plastic.

GAS:

Gas is one of the three states of matter. In gas, the forces that bind its elements together are not as strong as those in solids or liquids. These forces are not to be confused with the forces of attraction within the molecules. There are transitions between the states of matter. For instance, wax is solid at room temperature, melts when a candle is lit and evaporates at a very high temperature. The fourth and fifth states of matter found on earth are Plasma and Bose-Einstein Condensate respectively. In Plasma, the matter is 'ionized' and conducts electricity.