Question

b) We heat the neck of a glass bottle in order to remove the firmly fitted stopper.
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Answer 1

Answer:

If you run hot water on a bottle neck,the heat is applied directly to the bottle and only indirectly to the stopper inside the bottle. So, the bottle heat up first and thereby expands sooner then the stopper does. An expanded bottle will exert less pressure on the stopper and thus the stopper can easily be removed.