AQA A Level Physics - Gas Laws (Thermal)

Paper 2 ---- Specification: https://www.aqa.org.uk/subjects/physics/a-level/physics-7408/specification/subject-content/further-mechanics-and-thermal-physics-a-level-only#Further_mechanics_and_thermal_physics_A-level_only

What does Boyle’s law investigate?

The relationship between pressure and volume of a fixed mass of gas at a constant temperature.

What is Boyle’s law?

At constant temperature, pressure is inversely proportional to volume.

What equation represents Boyle’s law?

pV = constant or p₁V₁ = p₂V₂.

What variables are involved?

• Independent: volume.

• Dependent: pressure.

• Control: temperature and amount of gas.

How would you investigate Boyle’s law?

Trap a fixed mass of gas, vary its volume and measure the pressure each time while keeping temperature constant.

What graph would verify Boyle’s law?

A graph of p against 1/V should be a straight line through the origin.

Why must temperature remain constant?

Boyle’s law only applies at constant temperature.

Why should you wait between readings?

To allow the gas to return to thermal equilibrium with its surroundings.

What does Charles’s law investigate?

The relationship between volume and absolute temperature at constant pressure.

What is Charles’s law?

At constant pressure, volume is directly proportional to absolute temperature.

What equation represents Charles’s law?

V/T = constant.

What variables are involved?

• Independent: temperature.

• Dependent: volume.

• Control: pressure and amount of gas.

How would you investigate Charles’s law?

Heat a fixed mass of gas and measure its volume at different temperatures while keeping pressure constant.

What graph would verify Charles’s law?

A graph of V against T (in kelvin) should be a straight line through the origin.

Why must temperature be measured in kelvin?

Gas laws use absolute temperature.

Why must pressure remain constant?

Charles’s law only applies when pressure is constant.

What are the main sources of uncertainty?

Reading pressure, volume and temperature scales.

How could you improve accuracy?

Take repeated readings, use precise instruments and allow the gas to reach thermal equilibrium.

What is pressure law?

At constant volume, pressure is directly proportional to absolute temperature.

What is the equation for pressure law?

• p/T=constant

• p1t1 = p2t2

What variables are kept constant?

Volume and mass of gas.

What happens to pressure when temperature increases?

Pressure increases because particles have greater average kinetic energy and collide with the walls more frequently/with greater momentum.

What graph demonstrates pressure law?

A graph of pressure against temperature in kelvin gives a straight line through the origin.

Why must temperature be measured in kelvin?

The relationship is proportional to absolute temperature, not °C.

How can pressure law be explained using kinetic theory?

Higher temperature → greater average molecular kinetic energy → more frequent/forceful collisions with the container walls → greater pressure.