Gay-Lussac's Law
At constant volume, P is proportional to Kelvin temperature.
About this topic
Gay-Lussac's law states that at constant volume, the pressure of a fixed amount of gas is directly proportional to its absolute temperature: P1/T1 = P2/T2. Heating a sealed container raises the pressure because particles move faster and hit the walls harder and more often.
Because the volume cannot change in a rigid container, extra energy only shows up as higher pressure. A plot of pressure against kelvin temperature is a straight line through the origin. Always use kelvin; the pressure units must match on both sides. The law is named after Joseph Louis Gay-Lussac, who studied gases in the early 1800s.
Worked example: a tyre at 220 kPa and 280 K warms up to 310 K during a long drive. P2 = 220 x 310 / 280 = 244 kPa. Aerosol cans carry warnings not to be heated because the pressure can rise enough to burst them, and pressure cookers use the idea to reach higher temperatures to cook food faster. Tyre pressures in winter often drop, causing warning lights.
Students sometimes confuse this law with Charles's law; the difference is what is held constant (volume here, pressure there). A useful memory trick is to link each law with the property that does not change. Also, avoid Celsius, and remember that this law needs a sealed container.
Key ideas
- P₁/T₁ = P₂/T₂
- Pressure cookers
- Heated cans can burst
Quick check
Use cases: where Gay-Lussac's Law helps
- Homework: review the key idea behind Gay-Lussac's Law before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Gay-Lussac's Law without notes.
- Visual learning: play with the interactive lab to see how Gay-Lussac's Law changes when you adjust its inputs.
- Teaching a friend: explain Gay-Lussac's Law in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Gay-Lussac's Law?
At constant volume, P is proportional to Kelvin temperature.
What will I learn in Gay-Lussac's Law?
P₁/T₁ = P₂/T₂. Pressure cookers. Heated cans can burst.
Is Gay-Lussac's Law part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Gay-Lussac's Law lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Gay-Lussac's Law?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.