# Charles's Law (Law of Volumes)

- Page ID
- 3804

Charles' Law |
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For a fixed mass of gas at constant pressure, the volume is directly proportional to temperature (in Kelvin). This is mathematically \[ V = constant x T \] |

That means, for example, that if you double the temperature from, say to 300 K to 600 K, at constant pressure, the volume of a fixed mass of the gas will double as well. You can express this mathematically as

**Is this consistent with pV = nRT ?**

- You have a fixed mass of gas, so n (the number of moles) is constant.
- R is the gas constant.
- Charles' Law demands that pressure is constant as well.

If you rearrange the pV = nRT equation by dividing both sides by p, you will get

**V = nR/p x T**

But everything in the nR/p part of this is constant. That means that V = constant x T, which is Charles' Law.

## Contributors and Attributions

Jim Clark (Chemguide.co.uk)