22. Explain how iron rim fixed on the bullock cart wheel? What type of change caused by?
23. Explain the types of changes with example.
Answers
Explanation:
22 . To fix iron rim on the bullock cart it is first heated .Due to heating the rim expanded .Then it is placed over the wheel . After placing it over wheel it is then cooled by pouring water over it .It
is cooled, so that it contracts and fixed tightly over wheel. It is caused by chemical change .
23. There are four type of changes:-
1. Reversible change: The change which can be reversed again by reversing the conditions is called reversible change .
For ex - boiling of water
2. Ireversible change: It is just opp. of reversible change . For ex - tearing of paper
3. Physical change: The change in which no new substance with no change in chemical properties and composition is formed is called physical change .It is a temporary change . For ex - melting of ice
4. Chemical change: The change in which new substance with entirely different chemical properties and composition is formed is
called chemical change . It is a permanent change .For ex - burning of paper