Explain Physical and Chemical change.

Physical change is the change of that matter where only appearance or molecular arrangement of matter changes without changing its composition.

Examples: Boiling and freezing of water, melting of wax, mixing sand and grains, crumpling a paper bag, chopping a wood etc.

Properties of physical change are as follows:

• Most of the physical changes are reversible. Original form of the matter can be attained.

• It is a temporary change and no new substance is formed.

• During a physical change, no energy is absorbed or released

• Physical change causes a change in physical properties such as shape, size, etc.

The change in which chemical properties of the matter change is known as chemical change.

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

For example, photosynthesis reaction is a chemical change as carbon dioxide and water in the presence of sunlight and chlorophyll to give sugar molecule and oxygen as a product. Here, sugar once formed cannot be converted back to carbon dioxide and water easily. As the new compound is formed from the reaction between water and carbon dioxide, it is a chemical change.

Other Examples: Digestion of food, burning of petrol and diesel, rusting, preparation of tea and coffee, etc.