AQA GCSE Physics Physics Paper 1 (Foundation), June 2023: Question 7

10 marks · Standard Demand difficulty · Short Answer

Investigate the relationship between the pressure and volume of a fixed mass of gas at constant temperature, including plotting a graph, calculating the pressure-volume constant, and explaining gas particle behaviour.

Practise this question

Question

Question text

07 A teacher demonstrated the relationship between the pressure and the volume of a

fixed mass of gas at a constant temperature.

Figure 9 shows the equipment used.

Figure 9

07.1 Complete the sentence.

Choose the answer from the box.

[1 mark]

circular paths random directions the same direction

Particles in a gas move in 29 .

07.2 Complete the sentence.

Choose the answer from the box.

[1 mark]

a constant speed a constant velocity a range of speeds

Particles in a gas move with 30 .

07.3 Table 6 shows some of the results.

Table 6

Pressure in kPa Volume in cm3

300 10

200 15

150 20

120 25

100 30

Complete Figure 10. The first point has been plotted for you.

You should:

• plot the points from Table 6

• draw the line of best fit.

[3 marks]

Figure 10

07.4 The relationship between the pressure and the volume of a gas is given by

the equation:

pressure × volume = constant

Calculate the constant when the pressure of the gas was 300 kPa.

Use Table 6.

[2 marks]

Constant = kPa cm3

07.5 When the volume of the gas increases, the pressure in the gas decreases.

The temperature of the gas stays the same.

How does increasing the volume affect each of the following quantities?

[3 marks]

Tick ( ) one box in each row.

Stays the

Quantity Decreases Increases

same

Mean time between collisions

of the particles with the tube

Mean distance between the

particles

Mean speed of the particles

Mark scheme

Show the mark scheme

Question 7

AO /

Question Answers Extra information Mark

Spec. Ref.

07.1 random directions 1 AO1

4.3.3.1

AO /

Spec. Ref.

07.2 a range of speeds 1 AO1

4.3.3.1

AO /

Question Answers Mark

Spec. Ref.

07.3 3 AO2

4.3.3.2

2 marks for plotting 4 points correctly

1 mark for plotting 2 or 3 points correctly

1 mark for line of best fit – HYSICS – –

AO /

Spec. Ref.

20 07.4 AO2

300 × 10 = constant allow use of any correct pair of 1 4.3.3.2

values

constant = 3000 1

AO /

Spec. Ref.

07.5 AO1

4.3.3.2

Stays the

Quantity Decreases Increases

same

Mean time between

collisions of the ✓ 1

particles with the tube

Mean distance

✓ 1

between the particles

Mean speed of the

✓ 1

particles

additional tick in a row negates the mark for that row

Total Question 7 10

How to answer it

Gas Pressure, Volume & Particle Motion

WHAT THIS QUESTION TESTS

Core Revision Topics:

Particle Theory of Gases: Describing particle motion in terms of direction and velocity distribution.
Boyle's Law & Data Skills: Plotting non-linear scientific data accurately on a grid and drawing a smooth curve of best fit.
Mathematical Calculation: Applying the constant relationship pressure × volume = constant using given tabular data.
Microscopic Explanations: Explaining macroscopic gas behavior (pressure, volume, temperature) through particle spacing, collisions, and thermal kinetic energy.

PART 07.1 • 1 MARK

Direction of Gas Particle Motion

AQA Specification Reference: 4.3.3.1 (Particle model in a gas)

✅ Correct Answer

Particles in a gas move in random directions.

💡 Key Knowledge

Gas particles undergo continuous, rapid, and completely random motion. They collide elastically with each other and the container walls, constantly changing direction.

🧠 Exam Technique

Choose only from the options provided in the box. Do not overthink: gas particles never travel along orderly paths like "circular paths" or all in "the same direction".

❌ Common Errors

Confusing gas particles with macroscopic currents (e.g. convection currents moving upward). Individual molecules move entirely at random.

Mark scheme: [1 mark] for random directions .

PART 07.2 • 1 MARK

Distribution of Particle Speeds

AQA Specification Reference: 4.3.3.1 (Velocity distribution)

✅ Correct Answer

Particles in a gas move with a range of speeds.

💡 Key Knowledge

Even at a fixed temperature, individual gas molecules do not all have identical kinetic energy. Some move slowly, most move at medium speeds, and a few move extremely fast (Maxwell-Boltzmann distribution).

🧠 Exam Technique

Remember that temperature is proportional to the average kinetic energy of particles, not that every single particle has the same speed.

❌ Common Errors

Selecting "a constant speed" because the question mentioned the gas was at a constant temperature. Temperature sets the average, not individual speeds.

Mark scheme: [1 mark] for a range of speeds .

PART 07.3 • 3 MARKS

Plotting Pressure vs Volume (Boyle's Law Curve)

AQA Specification Reference: 4.3.3.2 (Pressure in gases)

✅ Plotting Coordinates & Curve

Points to plot (Volume on x-axis, Pressure on y-axis):

(10, 300) — already plotted as an example
(15, 200)
(20, 150)
(25, 120)
(30, 100)

Line of best fit: A single, smooth, continuous curve sloping downwards from left to right through the points.

🧠 Drawing the Line of Best Fit

Use neat small crosses (×): Dots can get lost; large blobs lose accuracy marks. Plots must be within ±½ small square.
Recognise the shape: Pressure is inversely proportional to volume ( p ∝ 1/V ), giving a smooth hyperbola curve.
Never use a ruler to connect points point-to-point (zig-zag). Do not force the curve to hit (0,0).

❌ Common Plotting Traps

Reading the scale: On the y-axis, 5 small squares = 50 kPa (1 small square = 10 kPa). On the x-axis, 5 small squares = 5 cm³ (1 small square = 1 cm³). Misreading (25, 120) was the most common plotting mistake.
Multiple/feathered strokes: Sketching back and forth with a blunt pencil creates a fuzzy line that loses the curve mark.

Mark scheme:

[2 marks] for plotting 4 points correctly (within ½ small square). [1 mark] if 2 or 3 points plotted correctly.
[1 mark] for a smooth line of best fit (curved, no kinked straight segments).

PART 07.4 • 2 MARKS

Calculating the Constant (pV = constant)

AQA Specification Reference: 4.3.3.2 (Calculations with Boyle's Law)

📐 Step-by-Step Calculation

Formula given: pressure × volume = constant

Identify values from Table 6:
When Pressure = 300 kPa, Volume = 10 cm³
Substitute into formula:
300 × 10 = constant (1 mark)
Calculate final value:
constant = 3000 (1 mark)

💡 Alternative Valid Value Pairs

Any row from Table 6 produces the same constant:

200 × 15 = 3000
150 × 20 = 3000
120 × 25 = 3000
100 × 30 = 3000

The unit kPa cm³ is already provided on the answer line, so no unit conversion into Pa or m³ was required.

❌ Common Errors

Dividing instead of multiplying: Writing 300 / 10 = 30 . Always read the formula carefully: it says pressure × volume.
Unnecessary conversions: Converting 300 kPa to 300,000 Pa and 10 cm³ to m³. While mathematically valid if units are changed, students often introduce arithmetic mistakes when doing this.

Mark scheme: [1 mark] for substitution 300 × 10 (or any row) • [1 mark] for final value 3000 .

PART 07.5 • 3 MARKS

Microscopic Effects of Increasing Volume

AQA Specification Reference: 4.3.3.2 (Qualitative understanding of pressure changes)

✅ Correct Table Responses

Quantity	Stays the same	Increases
Mean time between collisions of the particles with the tube		✓
Mean distance between the particles		✓
Mean speed of the particles	✓

💡 Physical Explanations (Why?)

Collision time INCREASES: The tube has a larger volume, so particles must travel longer distances between impacts with the container walls. Hence, the time between impacts goes up.
Distance between particles INCREASES: The same number of particles now occupy more space, meaning they are spread out further apart.
Mean speed STAYS THE SAME: The question states: "The temperature of the gas stays the same." Because temperature determines the average kinetic energy (and thus speed) of the particles, their speed cannot change!

❌ Examiner Warning: Multiple Ticks

The mark scheme strictly states: "additional tick in a row negates the mark for that row".

If you change your mind, cross out the incorrect tick completely so the examiner clearly knows which box you intend to select.

Mark scheme: [1 mark] per correct row. Any row containing more than one tick receives 0 marks.

Topics

Physics · P3: Particle Model of Matter

Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 1 (Foundation), June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.