Beginner Topic 229 of 1102 States of Matter & Solutions
Gay-Lussac's Law
At constant volume, gas pressure is directly proportional to its absolute temperature.
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In-depth explanation of Gay-Lussac's Law
Gay-Lussac's law states that at constant volume and fixed amount of gas, the pressure is directly proportional to the absolute temperature, so P/T is constant. Heating increases particle speed and the rate and force of collisions with the container walls, so the pressure rises. The relation P1/T1 = P2/T2 requires the temperature to be in kelvin, because only then does zero correspond to no molecular motion. The law explains why the pressure in a car tyre rises after driving, when friction warms the air inside. It is also the reason sealed aerosol cans are dangerous when left in a fire or a hot car.
Going deeper: Gay-Lussac's Law
Key ideas: Use P1/T1 = P2/T2 with fixed volume and moles, and temperature in kelvin. For a rigid container, a 10 percent rise in absolute temperature raises pressure by 10 percent. It is the basis for safety limits on sealed containers and for tyre pressure checks, which should be done with cold tyres.
Common mistakes and connections: Do not confuse this law with Gay-Lussac's law of combining volumes, which concerns gas reaction ratios. Using Celsius values is again the typical error. Also, tyre gauges read gauge pressure, so absolute pressure must be used in the ratio. Connects to kinetic theory, the combined gas law and pressure cooker design.
Visualization of Gay-Lussac's Law
At constant volume pressure rises in direct proportion to kelvin temperature, which is why sealed containers burst when heated. The interactive lesson shows this as a live animation or chart.
Worked example and use case
A sealed tank at 2.0 atm and 300 K, heated to 450 K at constant volume, reaches 3.0 atm.
Frequently asked questions about Gay-Lussac's Law
What is Gay-Lussac's Law?
At constant volume, gas pressure is directly proportional to its absolute temperature.
Is Gay-Lussac's Law a beginner, intermediate or advanced topic?
Gay-Lussac's Law is a beginner topic in States of Matter & Solutions. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Gay-Lussac's Law?
Study these earlier topics in States of Matter & Solutions first: Standard Temperature and Pressure, Boyle's Law, Charles's Law.
What comes after Gay-Lussac's Law?
The next topics in States of Matter & Solutions are Avogadro's Law and Combined Gas Law.
Can I practise Gay-Lussac's Law with quizzes?
Yes. The interactive lesson includes a self-check question on Gay-Lussac's Law, and the States of Matter & Solutions quiz draws on every topic in this area.
Where Gay-Lussac's Law fits in States of Matter & Solutions
Gay-Lussac's Law is topic 10 of 109 in States of Matter & Solutions.