Question

1.
Give two differences between reversible and irreversible changes.
2.
Formation of curd is an irreversible as well as a chemical change. Justity
this statement.
3:
Water cycle is a natural change. Classify it as a (1) physical
(ii) a reversible or irreversible change. Also, justify your answer
4 :How can we say that burning of candle is a chemical change but the glowing
of bulb is a physical change?​

Answer 1

Answer:

• reversible change     ----     A change which can happen backward, that is, can be reversed is called a reversible change                             irreversible change   -----    A change which cannot happen backward, that is, it cannot be reversed is called an irreversible change.

• During the formation of the curd from the milk the chemical composition is changed, so it is considered to be chemical change. Once Curd formed from Milk it cannot revert back to milk, so it is an irreversible change.
• physical change
• during burning of candle new substances like carbon dioxide gas and water vapour are produced, hence it is a chemical change  but Glowing of an electric bulb is a physical change because  no new substance with different properties is formed.Mar