Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron filings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of a candle.

During a chemical reaction, the chemical bonds between the molecules are broken and rearranged, and new bonds are formed resulting in the formation of new compounds.

Properties of chemical change are as follows:

1. Chemical changes are irreversible. The original form of the matter cannot be attained.

2. It is a permanent change and one or more new substance is formed.

3. During a chemical change, energy is produced in the form of heat, light or sound.

4. Chemical change causes changes in the physical and chemical properties of the substance.]