An aluminium saucepan is filled with cold water and placed on a hot plate. The hot plate is switched on and, as the temperature of the water in the saucepan increases, the internal energy of the water increases.
State what is meant by an increase in internal energy.
Eventually, the water reaches boiling point. Thermal energy from the hotplate is still being transferred to the water. Explain, in terms of molecules, the effect of this thermal energy on the water during boiling.
