Charles’s law states that if a given quantity of gas is held at aconstant pressure, its volume is directly proportional to the absolutetemperature. Think of it this way. As the temperature of the gasincreases, the gas molecules will begin to move around more quickly andhit the walls of their container with more force—thus the volume willincrease. Keep in mind that you must use only the
Kelvintemperature scale when working with temperature in all gas lawformulas! Here’s the expression of Charles’s law that you shouldmemorize:
UCQ7?"PGz Q&W Try using Charles’s law to solve the following problem.
Example
A sample of gas at 15ºC and 1 atm has a volume of 2.50 L. What volume will this gas occupy at 30ºC and 1 atm?
Explanation
The pressure remains the same, while the volume and temperature change—this is the hallmark of a Charles’s law question.
So, 
, then 2.50 L/288K = V2/303K, and V2 = 2.63 L
This makes sense—the temperature isincreasing slightly, so the volume should increase slightly. Be carefulof questions like this—it’s tempting to just use the Celsiustemperature, but you must first convert to Kelvin temperature (byadding 273) to get the correct relationships!
