Question

Question #74685

Answer 1

See below.

Explanation:

An isothermal process is one in which the temperature of the system remains constant.

The first law of thermodynamics gives us the equation:

`DeltaE=W+Q`

Where `DeltaE` is the change in internal energy of the system, given by `E=mcDeltaT`, `W` is the work done by the system, and `Q` is the energy input into the system by heating.

We see that `DeltaE` depends on the temperature `DeltaT`, and indeed if the temperature does not change, then `DeltaT=0` and consequently `DeltaE=0`.

Therefore, for an isothermal process, `Q_"in"=-W_"out"`.

An example of an isothermal process is evaporation (so long as it occurs at constant pressure, which is usually the case).