Physics · May / June 2024 · Paper 11 · Question 20

A glass beaker contains water. When the centre of the base of the beaker is heated, a convection current is set up. [diagram: glass beaker containing water, with a convection current shown by dashed arrows; heat applied at the centre of the base] Which statement explains this?

1. AThe evaporation of water causes water molecules to rise to the surface.
2. BThe expansion of water molecules causes them to rise to the surface.
3. CThe water above the heat source rises because it becomes less dense.
4. DThe water at the side falls because it becomes less dense.

As printed in the paper