## Calculating entropy of vaporization

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Tim Foster 2A
Posts: 73
Joined: Fri Sep 29, 2017 7:07 am

### Calculating entropy of vaporization

When finding entropy of vaporization from a temperature that is not the boiling point, we include the change in entropy that arises when you cool the vapor back down to original temperature. Why is this last value calculated using the heat capacity for the gaseous state? Why does cooling down a vapor below its boiling point not condense it back into a liquid, thus necessitating the use of heat capacity for the liquid state?

Jason Liu 1C
Posts: 52
Joined: Fri Sep 29, 2017 7:04 am

### Re: Calculating entropy of vaporization

I don't think cooling a vapor down to under its boiling point takes away enough kinetic energy from the molecules to cause them to condense. For example, at room temperature, there is still water vapor in the air. However, a cold bottle in the room will cause the water vapor to condense on the bottle.