As shown in Fig. 3.1, water is heated by two different kettles. The picture includes an electric kettle and a gas-heated kettle with a gas burner. The information for both kettles is given in Fig. 3.2.
(a(i))[2]
Calculate the electric kettle's efficiency.
(a(ii))[2]
Calculate the useful power of the gas heated kettle.
(b)[1]
Both kettles contain the same mass of water, and both start at the same initial temperature. State and explain which kettle reaches boiling point first.
(c)[1]
The boiling water gives steam at $100\,^{\circ}\text{C}$. State one difference between the molecules in the steam and the molecules in the boiling water.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Efficiency is found from useful energy / input energy” …