(a)[2]
State what the internal energy of a system means.
(b(i))[3]
State and explain qualitatively the change, if any, in the internal energy of the following system: a lump of ice at $0^{\circ}\text{C}$ changes into liquid water at $0^{\circ}\text{C}$.
(b(ii))[3]
State and explain qualitatively the change, if any, in the internal energy of the following system: a cylinder containing gas at constant volume is in sunlight so that its temperature rises from $25^{\circ}\text{C}$ to $35^{\circ}\text{C}$.