What are Physical and Chemical Changes?

 Physical change

Physical change is the change by which the physical properties of a substance change. These physical properties can be in the form of size, state, color, form and smell of a substance. But the matter remains the same. No new matter is formed from it.

Examples

1. Kept water in the fridge, took it out after some time and it became ice due to the cold of the fridge. This Ice is frozen water. The matter is the same but some of the physical properties of the substance like state, taste and shape have changed.

2. Water was boiled, it turned into water vapor, once water was liquid, now it is gas and has become invisible to the eyes.

3. The steam was cooled in a glass and it again became water.

4. Jaggery was added to water and mixed and it became a different colour. Which is not the color of water and not the color of jaggery, which has the properties of jaggery and water, this is also a physical change.

5. Sugarcane juice was boiled and it became jaggery due to physical change.

6. A chair is made after cutting a tree, but the chair is made of wood and the wood obtained from the tree is the same origin and the chair is the physical transformation of the tree.

Chemical changes

Chemical change is the change due to which when two or more substances are mixed together, there is a reaction between them due to which new substances are produced whose properties are completely different from the properties of the previous substance. 

Example 1.

See rust on iron shed where oxygen and water possible

Iron + Oxygen + Water => Rust (Fe 2 O 3 ) or Iron Oxide

This rust formation is a chemical change which

Formed by the contact of Fe + O 2 with water i.e. H2 O which destroys iron and this is a chemical change due to which the substances made from it are of no use to us and it also destroys the properties of iron, hence it is changed every year. Painting is necessary if you have iron doors or sheets.

Example 2

There is an ozone layer above our atmosphere which reacts with the ultraviolet rays coming from the sun to form oxygen and protects us from this natural chemical change.

Example 3

  There are chemical elements inside us too which interact with food and help in digestion, which helps in producing blood and other seven elements energy and increases our strength.