# Volume of gas at STP question? Don't understand.

## An ideal gas with a volume of 1 liter at STP is placed into a piston chamber that can freely change volume. The volume is measured as the temp is lowered. The gas will achieve its minimal volume at?

Apr 7, 2017

Cool question!

#### Explanation:

The trick here is to realize that you will keep lowering the temperature of the gas until it will no longer be a gas.

In other words, the molecules that make up the gas will only be in the gaseous state until a specific temperature is reached $\to$ the boiling point of the gas.

Once you hit the boiling point, the gas will become a liquid. At that point, its volume is, for all intended purposes, constant, meaning that you cannot hope to compress it further by decreasing the temperature.

Therefore, the answer would be the boiling point of the gas. Mind you, the fact that you're working under STP conditions, i.e. a pressure of $\text{100 kPa}$ and a temperature of ${0}^{\circ} \text{C}$, implies that the gas has a boiling point that is $< {0}^{\circ} \text{C}$.