Classify the changes involved in the following processes as physical or chemical changes: 

(a) Photosynthesis 

(b) Dissolving sugar in water 

(c) Burning of coal 

(d) Melting of wax 

(e) Beating aluminium to make aluminium foil 

(f ) Digestion of food

Changes in your surroundings are of two types: Physical change and Chemical change.

A change in which a substance undergoes a change in its physical properties like shape, size, color or state is called a physical change. It can be either reversible or irreversible. It doesn't include the production of new substances.

Water freezing to form ice is an example of a reversible physical change. An egg being cracked or wood being ground into sawdust is an example of an irreversible physical change.

A change in which one or more new substances are formed is called a chemical change or a chemical reaction. It is an  irreversible change.

Digestion of food, decomposition of waste etc., are an examples of irreversible chemical change.