Question

A water molecule gains enough energy to enter the gas phase is chemical or physical?why?

Answer 1

It is a physical change becasue the chemical makeup of the water molecule did not change - the molecule just changed state.

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Answer 2

Physical because you are not changing the substance. For example water vapor(gas) can be condensed back into water. If you burn a piece of paper the ash cannot be changed back into paper therefore it is chemical. But because you are not changing the substance the answer is physical.