Which of the following explains why a convection current is formed in a gas when it is heated from below?
The heated gas expands and its density decreases, causing it to rise.
The individual molecules in the heated gas expand, causing them to float upwards.
The heated gas contracts and its density increases, causing it to sink.
The molecules in the gas gain mass as they absorb thermal energy, causing them to fall.
73 exam-style questions on CIE IGCSE Physics 2.3.2 Convection. Each one has a worked solution and a mark scheme showing where the marks go.