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

∆U = 2.0 × 104 J

Process: isovolumetric

Step-by-step explanation:

Given: Q = 2 × 104 J,

Find: internal energy, ∆U

volume V remains constant, so W = 0

∆U = Q – W

∆U = Q

∆U = 2.0 × 104 J

Process: isovolumetric

Answer 2

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`