It is known that wax contracts on solidification. If molten wax is taken in a large vessel and it is allowed to cool slowly, then

Substances are classified into two categories(i) water like substances which expand on solidification.(ii) CO2 like (Wax, Ghee etc.) which contract on solidification.Their behaviour regarding solidification is opposite.Melting point of ice decreases with increase of pressure but that of wax etc increases with increase in pressure Similarly ice starts forming from top downwards whereas wax starts its formation from bottom