If glass expanded more than mercury, the column of mercury in a therometer would rise when:?

Question

a)the temperature increased
b)the temperature decreased
c) neither
I was told the answer is B, but I do not understand why. Can anyone explain?

Answer 1

If glass expanded more than mercury when heated, then the glass would also contract more than mercury when the thermometer cooled. The hollow center of the glass tube would also become smaller (because the glass tube is contracting) faster than the mercury would contract. This would squeeze the mercury, causing the level of the mercury to rise.
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