Charles's Law

Charles's Law says that if the pressure on a gas stays the same, making the gas hotter increases its volume, and making it colder decreases its volume. This happens because gas particles move faster when temperature rises, so they hit the container walls more often and with more force; if the pressure is held constant, the gas must take up more space to balance that out. The temperature must be measured in kelvin, because the relationship is proportional to absolute temperature, not Celsius.

Use this when a gas changes temperature but the pressure stays constant, such as in balloons, syringes with movable plungers, or gas trapped under a piston. It is also useful in chemistry and physics problems involving heating or cooling gases at constant pressure.

• Using Celsius instead of kelvin in the temperature values
• Applying the formula when pressure is not constant
• Mixing up initial and final values without keeping units consistent