Gas Laws, Quick Last-Minute Exam Revision Notes

Gas laws explain how gases behave when pressure, volume, temperature, and number of moles change.

These laws are important because they connect theory with real gas behavior in chemistry and physics.

1️⃣ Boyle’s Law

At constant temperature, pressure is inversely proportional to volume.

P₁V₁ = P₂V₂

✔ If pressure increases, volume decreases.
✔ Used when temperature remains constant.

2️⃣ Charles’s Law

At constant pressure, volume is directly proportional to temperature in Kelvin.

V₁ / T₁ = V₂ / T₂

✔ Higher temperature causes expansion of gas.
✔ Temperature must always be converted into Kelvin.

Check this Out

Pressure

Temperature

Volume

PV = nRT

3️⃣ Gay-Lussac’s Law

At constant volume, pressure changes directly with temperature.

P₁ / T₁ = P₂ / T₂

✔ Heating gas inside a closed container increases pressure.

4️⃣ Avogadro’s Law

At constant temperature and pressure, volume depends on number of moles.

V₁ / n₁ = V₂ / n₂

✔ More gas molecules occupy more space.

5️⃣ Combined Gas Law

Used when pressure, volume, and temperature all change together.

(P₁V₁)/T₁ = (P₂V₂)/T₂

✔ Useful when amount of gas remains constant.

6️⃣ Ideal Gas Law

This law combines all gas variables in one equation.

PV = nRT

Where:
P = pressure
V = volume
n = moles
R = gas constant
T = temperature in Kelvin

🎯 Quick Exam Points

✔ Boyle’s law shows inverse relationship.
✔ Charles, Gay-Lussac and Avogadro show direct relationship.
✔ Always use Kelvin temperature.
✔ Gas laws work best for ideal gases under low pressure and high temperature.

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