Question

Air is heated in a glass bottle. The heat energy added to the air is 2.0 × 104 joules. What is the change in internal energy of the gas? Identify the thermodynamic process.

Answer 1

The change in internal energy of the gas is $\Delta U = 2.0 \cdot 10^4 J$.

In fact, the 1st law of thermodynamics states that the change in internal energy of a system is equal to the amount of heat given to the system (Q) plus the work done on the system (W):
$\Delta U = Q+W$
In this example, no work is done on the bottle so W=0, while the heat given to the system is $Q=2.0 \cdot 10^4 J$, so the change in internal energy of the gas is
$\Delta U = Q = 2.0 \cdot 10^4 J$