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A physical change is one in which the shape, size, appearance or state, of a substance may alter, but its chemical composition remains same. No new substance is formed. It is usually a change, which is reversible. By reversing the process, the original substance can be obtained.
Example, by using a piece of gold, a goldsmith can make a large variety of ornaments. But all of them consist of the same substance, namely gold. A more common example is that of water, which can be converted into solid ice, liquid water, and gaseous water vapour. It can be reconverted to its previous state by various methods. Yet, in all the three forms, the chemical composition of water is not altered. No new substance with new chemical properties is formed. In all these, water consists of two atoms of hydrogen and one atom of oxygen.
Thus, a Physical change is a change, in which the chemical composition of the substance is not affected, i.e., no new substance is formed.
Dissolving of Sugar in Water
When sugar is dissolved in water, it seems to disappear completely, and not even a very powerful microscope can show us the molecules of sugar in water. However, the solution obtained is evenly sweet. By evaporating the water, the sugar can be recovered in a crystalline form.
Magnetising An Iron Rod
An iron rod can be converted into a magnet by passing an electric current through an insulated coil wound around. When the current flows, the iron bar gets magnetised. One end becomes North Pole and the other the South Pole. If the direction of the current is reversed, the North Pole changes to South Pole and the South Pole changes to North Pole.
Glowing of An Electric Bulb
When an electric current is passed through the filament of a bulb, the filament starts glowing and the glow stops as soon as the current is cut off.
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