A faulty mercury barometer contains a small amount of trapped air in the space above the mercury column. The temperature of this trapped air is increased.
As a result, the height of the mercury column decreases.
Why does this happen?
The trapped air molecules collide less frequently with the mercury surface.
The trapped air molecules exert more pressure on the mercury surface.
The density of the mercury in the column increases.
The atmospheric pressure acting on the open reservoir decreases.
126 exam-style questions on CIE IGCSE Physics 2.1.3a The absolute scale of temperature. Each one has a worked solution and a mark scheme showing where the marks go.