What is vapourization ? What is normal boiling point ?

A copper block of mass $2.5\; kg$ is heated in a furnace to a temperature of $500\,^{\circ} C$ and then placed on a large ice block. What is the maximum amount of ice (in $kg$) that can melt? (Specific heat of copper $=0.39\; J g ^{-1} K ^{-1}$ ;heat of fusion of water $=335\; J g ^{-1})$

Liquid oxygen at $50\  K$ is heated to $300\  K$ at constant pressure of $1\  atm$. The rate of heating is constant which of the following graphs represents the variation of temperature with time

If liquefied oxygen at $1$ atmospheric pressure is heated from $50\, K$ to $300\, K$ by supplying heat at constant rate. The graph of temperature vs time will be

What is called change of state of matter ?