Question

The internal energy of the gas in a gasoline engine cylinder increases by 200 J. Of 50 J of work is done by the gas, how much energy is added or removed as heat?

Answer 1

It is added 250J of energy as heat.

Step-by-step explanation:

First law of thermodynamics relates internal energy (
`\varDelta U`), work (W) and heat (Q) of a system in the next way:

`\varDelta U=Q+W`

Because we already know
`\varDelta U` and W values, the only thing we should do to find the energy removed (sign of Q negative) or added (sign of Q positive) as heat is solve (1) for Q:

`\varDelta U - W=Q`

Work is negative because is done by the gas to the surroundings, so W= -50J and
`\varDelta U` is positive becuse it increases, then:

`Q=200J-(-50J) =250J`

Because the sign of Q is positive heat is added to the engine.