Burning of a candle is a chemical as well as physical change as it involves change in both chemical and physical properties.
Everything around us undergoes certain changes. Changes can be either physical or chemical. The term ‘matter’ refers to anything that has mass and occupies space. It is made up of tiny particles and has physical and chemical properties.
A substance is said to undergo a physical change when only the physical properties such as the shape, size, colour, state or appearance of the substance change. Its chemical composition remains intact. Some characteristics of a physical change are:
- Temporary in nature.
- Does not affect the internal structure of a substance, only the molecules are rearranged.
- No new substance is formed.
- Most of the physical changes are reversible. We can obtain the substance back even after the change.
Examples of physical change
Some examples of a physical change are folding of a paper sheet, melting of wax, freezing and boiling water, melting of ice, condensation, vaporization, magnetizing a compass needle, dissolving sugar in water, etc.
A substance is said to undergo a chemical change when the chemical properties of a substance alter. As a result, there is either formation or breaking of atomic bonds at the molecular level. Some characteristics of a chemical change are:
- Permanent in nature.
- Since the original composition of the substance changes, one or more new substances are formed.
- Forms of energy, such as heat, light or electricity, may be emitted or absorbed.
- A chemical change is generally irreversible. At least, it cannot be reversed by simple physical means
Examples of chemical changes
Some examples of a chemical change are burning of paper, burning of fuel, rusting of iron, the souring of milk, growth in a living being, cooking, digestion of food, burning of wood, etc.