(a)[2]
State what internal energy means.
(b)[4]
Fig. 2.1 shows how the pressure $p$ of an ideal gas changes with volume $V$ as it goes through a cycle ABCA of changes. The temperature of the gas at A is $290\,\text{K}$. The temperature at B is $870\,\text{K}$. Determine (i) the amount, in mol, of gas, (ii) the temperature of the gas at C.
(c)[2]
Explain why the change from C to A involves external work and a change in internal energy.
(i)[2]
Determine the amount of gas, in mol.
(ii)[2]
Determine the temperature of the gas at C.