Ideal gas molecules

Question 1

Why do gas molecules exert pressure on the walls of a container?

Answer 1

• Gas molecules move in random motion.
• They collide with the walls of the container, exerting a force.
• Since pressure = force / area, these collisions create gas pressure.
• More frequent and forceful collisions increase pressure.

Question 2

What is absolute zero?

Answer 2

• The lowest possible temperature where particles have no kinetic energy.
• Absolute zero is -273°C (0 K).
• At this temperature, gas molecules stop moving.

Question 3

What is the Kelvin scale, and how do you convert between Kelvin and Celsius?

Answer 3

• The Kelvin scale starts at absolute zero (0 K = -273°C).
• To convert: K = °C + 273 and °C = K - 273.
• Used in gas laws because temperature in Kelvin is proportional to kinetic energy.

Question 4

Why does increasing temperature increase the speed of gas molecules?

Answer 4

• Higher temperature means more kinetic energy.
• Gas molecules move faster and collide more frequently.
• This increases pressure (if volume is constant) or expands volume (if pressure is constant).

Question 5

How is Kelvin temperature related to the average kinetic energy of molecules?

Answer 5

• Directly proportional – doubling Kelvin temperature doubles average kinetic energy.
• Higher temperature means molecules move faster.
• Used in gas laws to predict behaviour at different temperatures.

Question 6

What is the relationship between pressure and volume at constant temperature?

Answer 6

• Boyle’s Law: At constant temperature: P₁V₁ = P₂V₂.
• If volume decreases, molecules have less space and collide more frequently, increasing pressure.
• If volume increases, pressure decreases because molecules spread out.

Question 7

What is the relationship between pressure and temperature at constant volume?

Answer 7

• At constant volume: P₁/T₁ = P₂/T₂.
• Higher temperature increases kinetic energy, leading to more forceful collisions.
• This increases pressure inside the container.

Question 8

How can you investigate Boyle’s Law (pressure and volume relationship)?

Answer 8

Method:
1. Use a sealed gas syringe connected to a pressure sensor.
2. Change the volume and measure the pressure.
3. Plot a graph of P against 1/V – should be a straight line.
4. Confirms that pressure × volume = constant.
5. Shows that as volume decreases, pressure increases.

Question 9

How can you investigate the pressure-temperature relationship?

Answer 9

Method:
1. Use a sealed container with gas and a pressure sensor.
2. Gradually heat the container and record pressure at different temperatures.
3. Convert temperatures to Kelvin.
4. Plot a graph of pressure vs temperature (Kelvin).
5. Should be a straight-line graph, confirming P ∝ T.