Question

Why there are two types of coefficient of expansion of gas?

Answer 1

the liquids gases also has no specific area and length and hence there are no linear and areal expansions for a gas. It is simply because the volume expansion of the gases so large such that it is not going to make a difference whether it is apparent expansion or real expansion.
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Answer 2

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The liquids gases also has no specific area and length .
hence there are no linear and arealexpansions for a gas.
It is simply because the volume expansion of the gases so large

such that it is not going to make a difference

whether, it is apparent expansion or real expansion.