CBSE Class 7 Answered

Physical Changes

• In a physical change, no new substances are formed.
• Changes in size, shape, state, and colour of a substance are the physical changes.
• The properties such as size, shape, state and colour of a substance are called its physical properties.
• So, we can say that a change in which a substance undergoes a change in its physical properties is called a physical change.
• In a physical change, the changes are temporary and can be easily reversed to form the original substance.

 Examples: Melting of ice and freezing of water

Chemical Changes

• In a chemical change, new substances are formed.
• The new substances formed have properties entirely different from the original substances.
• In a chemical change, a substance undergoes a change in its chemical properties.
• Chemical changes are also called chemical reactions.
• In a chemical change, the changes are permanent which can usually not be reversed to form the original substances.

Examples: Burning of Magnesium Ribbon