9. What are slow and fast changes? Give examples.

Ans: The changes which take place in a long period of time are called slow changes whereas that changes which take place in a short period of time are called fast changes. Examples: (a) Rusting of iron, formation of day and night, ripening of fruits, growing of trees are slow changes. (b) Burning of paper, stretching of rubber band, blowing of balloons, bursting of crackers are fast changes.