Physics 5054 · O Level · Melting, boiling and evaporation
Melting, boiling and evaporation — practice question
A beaker containing water is set on a hot-plate until it boils, as illustrated in Fig. 4.1. The hot-plate sits on a balance that records the mass of water in the beaker. The liquid remains boiling for a long period. Bubbles are seen in the boiling water.
(a)[1]
Identify what the bubbles contain.
(b)[3]
Calculate the specific latent heat of vaporisation of water.
(c)[2]
The beaker of water is removed from the hot-plate. Boiling ceases, but evaporation carries on and the water cools. Explain, using ideas about molecules, how evaporation causes cooling.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Water vapour / steam / water in gaseous form” …