Charles's Law: Temperature and Volume of Gases
Charles's Law states that at constant pressure, the volume of a gas is directly proportional to its absolute temperature. When you heat a gas, it expands; when you cool it, it contracts. This is why hot air balloons rise, why car tyre pressure changes with temperature, and why aerosol cans carry warnings about heat.
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Formula
Charles's Law Calculator
Calculate temperature or volume changes using Charles's Law: V₁/T₁ = V₂/T₂.
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Worked Example
Given:
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FAQs
Why must temperature be in Kelvin for Charles's Law?
Because the relationship requires absolute temperature. At absolute zero (0 K = -273.15°C), gas volume would theoretically reach zero. Using Celsius gives incorrect results because 0°C is not absolute zero — it is an arbitrary point on the Celsius scale.
How does Charles's Law explain hot air balloons?
Heating the air inside a balloon increases its volume (at constant atmospheric pressure), making it less dense than the surrounding cooler air. The buoyancy force exceeds the weight of the balloon and occupants, causing it to rise. Cooling the air causes the balloon to descend.
What is the combined gas law?
The combined gas law merges Boyle's Law (pressure-volume) and Charles's Law (volume-temperature) into: P₁V₁/T₁ = P₂V₂/T₂. This allows simultaneous changes in all three variables while the amount of gas remains constant.