Physics 9702 · AS & A Level · The first law of thermodynamics
The first law of thermodynamics — practice question
A gas of fixed mass starts with a volume of $5.00 \times 10^{-4}\,\text{m}^3$ at a pressure of $2.40 \times 10^{5}\,\text{Pa}$ and a temperature of $288\,\text{K}$. It is then heated while the pressure stays constant, so that in the final state the volume becomes $14.5 \times 10^{-4}\,\text{m}^3$ and the temperature is $835\,\text{K}$, as shown in Fig. 3.1.
(a)[3]
Show that these two states are evidence that the gas behaves as an ideal gas.
(b(i))[2]
The thermal energy transferred to the gas for this change is $569\,\text{J}$. Determine the external work done.
(b(ii))[2]
Find the change in internal energy of the gas. Indicate whether internal energy increases or decreases.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Initial $\frac{pV}{T} = 0.417$” …