AQA GCSE Physics Physics Paper 1 (Higher), June 2023: Question 9

Mark scheme

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Question 9

AO /

Question Answers Extra information Mark

Spec. Ref.

09.1 random allow all / any 1 AO1

ignore many different 4.3.3.1

AO /

Spec. Ref.

09.2 more (air) particles (in the tyre) 1 AO1

4.3.3.1

greater number of collisions with allow collisions with tyre (walls) 1 4.3.3.2

tyre (walls) per second are more frequent

allow greater rate of collisions

with tyre (walls)

do not credit MP2 if linked to an

increased air temperature or

increased speed / Ek of particles

ignore greater force per m2

AO /

Spec. Ref.

09.3 (as temperature increases the) allow particles move with 1 AO1

air particles have greater (mean) greater speeds (on average) 4.3.3.1

kinetic energy

(so) more collisions with tyre allow collisions with tyre (walls) 1

(walls) per second are more frequent

allow greater rate of collisions

with tyre (walls)

(and) greater force in each allow greater rate of change of 1

collision momentum in each collision

greater (mean) force per square allow ‘on a given area’ for ‘per 1

metre causes greater pressure square metre’

(on wall of tyre)

Total Question 9 7

How to answer it

Gas Pressure & Particle Motion in a Tyre

📋 What This Question Tests

This question assesses your understanding of the Particle Model of Matter (AQA 4.3.3):

Recalling the nature of gas particle motion (speed and direction).
Explaining pressure changes when adding mass at constant volume and temperature.
Constructing a multi-step causal explanation of how temperature increases pressure using particle kinetic energy, collision frequency, and impact force.

Part 09.1 • 1 Mark

Particle Motion in a Gas

Completing the description of air particle motion

✅ Correct Answer

Air particles in the tyre move quickly in random directions.

Also acceptable: all directions or any directions.

❌ Common Errors

Writing "many different" or "opposite" directions (specifically ignored by the mark scheme).
Stating they move in "circular" or "straight" paths without specifying randomness.

Mark Breakdown: 1 mark for the precise scientific descriptor random (or all / any).

Part 09.2 • 2 Marks

Pumping Air at Constant Temperature

Explaining pressure rise when more air is added

✅ Model Answer

There are more air particles in the tyre.
Leading to a greater number of collisions with the tyre walls per second (more frequent collisions).

🧠 Exam Technique: "Rate" Matters

Never just say "there are more collisions". You must specify a time frame:

Write "per second", "per unit time", or "more frequent collisions".
Always state where the collisions happen: with the tyre walls (particle-to-particle collisions do not cause tyre pressure).

❌ Major Misconception Trap

Do NOT mention particles moving faster!

The prompt explicitly states: "The volume and temperature do not change." Since temperature is directly proportional to mean kinetic energy, the particles have the same average speed. Mentioning higher speed or energy loses Mark 2.

Mark Breakdown: [1] More particles inside the fixed volume. [1] Increased rate / frequency of collisions with the walls.

Part 09.3 • 4 Marks

Temperature & Gas Pressure

Explaining why tyre pressure increases when temperature rises

✅ Full 4-Step Chain of Reasoning

As temperature increases, particles have greater mean kinetic energy (move faster).
There are more collisions with the tyre walls per second (more frequent collisions).
There is a greater force exerted in each collision.
This causes a greater force per unit area (or per square metre), which means greater pressure.

💡 The Pressure Formula Link

Pressure is defined by the relationship:

pressure = force ÷ area

Because the tyre volume is fixed, its surface area (in m²) stays constant. Increasing the total force acting on that area directly increases pressure.

🧠 How to Secure All 4 Marks

Top-scoring students always cover both effects of faster particles:

Frequency: They hit the walls more often.
Hardness/Force: They hit the walls harder (greater rate of change of momentum).

Missing either point drops you from 4 marks down to 2 or 3.

❌ Common Examiner Criticisms

Saying "particles expand" — particles never expand; the space between them changes.
Forgetting to define pressure as force per unit area or force per square metre in the conclusion.

Mark Breakdown:
• Mark 1: Greater mean kinetic energy / higher average speed.
• Mark 2: More frequent collisions with tyre wall (more per second).
• Mark 3: Greater force per individual collision (greater rate of change of momentum).
• Mark 4: Greater force per square metre / per unit area results in higher pressure.

Topics

Physics · P3: Particle Model of Matter