AQA GCSE Combined Science: Trilogy Physics Paper 2 (Foundation), June 2025: Question 2

11 marks · Low Demand difficulty · Short Answer

Investigate how the colour of water affects its rate of cooling by infrared emission, including identifying variables, calculating cooling rate, and completing a bar chart.

Practise this question

Question

Exam question about an investigation into how the colour of water affects its cooling time. Figure 3 shows a conical flask containing coloured water, with a digital thermometer displaying 80.0 °C and a digital timer displaying 00:00. The question contains parts 02.1 through 02.8: multiple choice questions on the independent variable, control variable, and apparatus to measure 200 cm³; a calculation of average rate of change of temperature using the provided formula (change in temperature / time taken); Table 1 listing colours (Red, Yellow, Green, Blue, Violet) and their rates of temperature change; a blank grid for Figure 4 to complete a bar chart; an estimation question for orange colour; and two fill-in-the-blank sentences choosing terms from given boxes (infrared, ultraviolet, x-rays; energy, rarefactions, temperature).
Question text

02 Food colouring can be used to change the colour of water.

A student investigated how the colour of water affects the time taken for the

water to cool.

This is the method used.

1. Put 200 cm3 of hot water into a conical flask.

2. Add four drops of food colouring to the water.

3. Place a digital thermometer in the water.

4. Start a timer when the temperature of the water is 80.0 °C.

5. Record the time taken for the water to cool to 65.0 °C.

6. Repeat steps 1 to 5 using different colours of food colouring.

Figure 3 shows the apparatus.

Figure 3

02.1 What was the independent variable in this investigation?

[1 mark]

Tick ( ) one box.

Colour of water

Final temperature of water

Volume of water 7

02.2 Which of the following was a control variable in this investigation?

[1 mark]

*06*Tick ( ) one box.

Initial temperature of water

Time taken for water to cool

Type of thermometer used

02.3 What equipment should have been used to make sure 200 cm3 of water was put in

the conical flask?

[1 mark]

Tick ( ) one box.

Beaker

Measuring cylinder

Metre rule

02.4 The student also tested water with no food colouring.

The temperature of the water changed from 80.0 °C to 65.0 °C in a time

of 5.0 minutes.

Calculate the average rate of change of temperature of the water.

Use the equation:

change in temperature

average rate of change of temperature =

time taken

[2 marks]

Average rate of change of temperature = °C/minute

Table 1 shows the results for the different coloured water.

*07* Table 1

Rate of change of temperature

Colour of water

in °C/minute

Red 6.1

Yellow 5.0

Green 4.3

Blue 4.0

Violet 3.7

02.5 Complete Figure 4.

You should:

• label the y-axis

• add a scale to the y-axis

• draw bars for the green water and the violet water.

[3 marks]

Figure 4

02.6 In the visible spectrum, orange light is between red light and yellow light.

*08*Estimate the rate of change of temperature if orange food colouring was used.

Use Table 1.

[1 mark]

Estimated rate of change of temperature = °C/minute

02.7 Complete the sentence.

Choose the answer from the box.

[1 mark]

infrared ultraviolet x-rays

The results show that the colour of the water affects the rate at which the

water emits .

02.8 Complete the sentence.

Choose the answer from the box.

[1 mark]

energy rarefactions temperature

The water in each conical flask cools down because the electromagnetic radiation

emitted by the water transfers .

Mark scheme

Show the mark scheme Mark scheme for Question 2 with 8 sub-questions, totalling 11 marks. 02.1 accepts 'colour of water' (1 mark, AO1). 02.2 accepts 'initial temperature of water' (1 mark, AO1). 02.3 accepts 'measuring cylinder' (1 mark, AO1). 02.4 awards 1 mark for substitution (80.0 - 65.0)/5.0 and 1 mark for answer 3 (AO2). 02.5 awards 1 mark for y-axis label with unit, 1 mark for scale of 1.0 per cm, and 1 mark for correctly plotted bars for Green and Violet within half a square (AO2). 02.6 accepts any value between 5.0 and 6.1 (1 mark, AO3). 02.7 accepts 'infrared' (1 mark, AO1). 02.8 accepts 'energy' (1 mark, AO1).

Question 2

AO /

Question Answers Extra information Mark

Spec. Ref.

02.1 colour of water 1 AO1

6.6.2.2

RPA 21

AO /

Spec. Ref.

02.2 initial temperature of water 1 AO1

6.6.2.2

RPA 21

AO /

Spec. Ref.

02.3 measuring cylinder 1 AO1

6.6.2.2

RPA 21

AO /

Spec. Ref.

02.4 80.0 – 65.0 65.0 – 80.0 1 AO2

allow 6.6.2.2

5.0 5.0

RPA 21

15.0

allow

5.0

= 3 (°C / minute) allow – 3 (°C / minute) 1

AO /

Spec. Ref.

02.5 y-axis labelled rate of change of unit must be present 1 AO2

temperature in °C / minute 6.6.2.2

RPA 21

y-axis scale of 1.0 °C / minute 1

per cm

bars plotted correctly allow a tolerance of ± ½ small 1

square

– – 8464/P/2F –

ignore width of bars

AO /

Spec. Ref.

02.6 answer between 5.0 and 6.1 do not accept 5.0 (°C / minute) 1 AO3

(°C / minute) 6.6.2.2

do not accept 6.1 (°C / minute) RPA 21

AO /

Spec. Ref.

02.7 infrared 1 AO1

6.6.2.2

6.6.2.4

RPA 21

AO /

Spec. Ref.

02.8 energy 1 AO1

6.6.2.2

RPA 21

Total Question 2 11

How to answer it

Cooling Rates and Infrared Radiation (Required Practical)

WHAT THIS QUESTION TESTS

This question assesses working scientifically skills and core physics knowledge based on RPA 21 (Investigating Infrared Radiation):

  • Identifying independent, control, and dependent variables in thermal cooling experiments.
  • Selecting suitable measuring apparatus for volume accuracy.
  • Calculating the average rate of change of temperature using formula substitution.
  • Data presentation: plotting bar charts, axis labelling with units, and choosing uniform scales.
  • Interpolating experimental trends from tables.
  • Understanding that all hot objects emit infrared radiation, transferring thermal energy to the surroundings.
Question 02.1 • 1 Mark

Identifying the Independent Variable

Identifying what is changed by the experimenter

✅ Correct Answer

Colour of water

1 Mark: Tick in the first box only.

💡 Key Knowledge

  • Independent variable: The factor that you deliberately change (here, different colours of food dye).
  • Dependent variable: The factor you measure (time taken to cool).
  • Control variables: Factors kept constant to ensure a fair test.
Question 02.2 • 1 Mark

Identifying the Control Variable

Recognising what must be kept the same for a fair test

✅ Correct Answer

Initial temperature of water

1 Mark: Tick in the first box only.

🧠 Exam Technique

Read step 4 of the method carefully: "Start a timer when the temperature of the water is 80.0 °C." Starting at the exact same starting temperature (80.0 °C) each time controls the initial rate of cooling!

❌ Common Errors

Selecting "Time taken for water to cool". That is the dependent (measured) variable, not a control variable.

Question 02.3 • 1 Mark

Selecting Measuring Apparatus for Liquids

Choosing the right volumetric equipment

✅ Correct Answer

Measuring cylinder

1 Mark: Tick in the second box only.

💡 Key Knowledge

A measuring cylinder has precise graduated scale markings and is designed to measure specific liquid volumes accurately. A beaker has approximate volume markings and is primarily used for holding or mixing liquids, not accurate measuring.

Question 02.4 • 2 Marks

Calculating the Rate of Temperature Change

Applying the given formula with given data

📐 Step-by-Step Calculation

Step 1: Calculate the change in temperature:
Change = 80.0 °C − 65.0 °C = 15.0 °C
Step 2: Substitute values into the equation:
Rate = 15.0 / 5.0
Step 3: Calculate the final answer:
Rate = 3 (or 3.0) °C/minute
Mark 1: Correct substitution: (80.0 − 65.0) / 5.0 or 15.0 / 5.0
Mark 2: Final answer of 3 (also allows −3 )

❌ Common Errors

  • Dividing by 60 to convert to seconds: the question specifically asks for units of °C/minute, so keep time in minutes (5.0).
  • Forgetting to find the difference between 80.0 °C and 65.0 °C and just dividing 80 or 65 by 5.
Question 02.5 • 3 Marks

Completing the Bar Chart

Labelling, scaling, and accurate plotting

✅ Mark Scheme Breakdown

  • Mark 1 (y-axis label): Rate of change of temperature in °C / minute (Must include the unit).
  • Mark 2 (y-axis scale): Even, linear scale where 1 large square (1 cm) = 1.0 °C/minute (numbers 0, 1, 2, 3, 4, 5, 6, 7 on major grid lines).
  • Mark 3 (Bars plotted):
    • Green: bar drawn to exactly 4.3 (± ½ small square)
    • Violet: bar drawn to exactly 3.7 (± ½ small square)

🧠 Exam Technique: Diagram Guidance

What your graph should look like:

  • Vertical axis marked from 0 up to 7 at regular intervals (each big square = 1 unit; each tiny square = 0.1 units).
  • Green bar: Exactly 3 small grid squares above 4.0.
  • Violet bar: Exactly 7 small grid squares above 3.0 (or 3 small squares below 4.0).
  • Keep bar widths consistent with Red, Yellow, and Blue, leaving gaps between each category.
Question 02.6 • 1 Mark

Estimating from Continuous Trends

Interpolating values using colour sequence

✅ Correct Answer

Any value greater than 5.0 and less than 6.1 °C/minute

Examples of acceptable values: 5.5, 5.6, 5.4

1 Mark: Any value strictly between 5.0 and 6.1.

❌ Common Errors

Do not write exactly 5.0 or 6.1. Orange lies between red (6.1) and yellow (5.0), so your estimate must be strictly inside that range.

Questions 02.7 & 02.8 • 2 Marks

Electromagnetic Radiation and Energy Transfer

Thermal physics recall

✅ Part 02.7 Answer

The results show that the colour of the water affects the rate at which the water emits infrared.

1 Mark: 'infrared' selected from the box.

✅ Part 02.8 Answer

The water in each conical flask cools down because the electromagnetic radiation emitted by the water transfers energy.

1 Mark: 'energy' selected from the box.

💡 Key Knowledge: Radiation & Cooling

  • All warm objects emit infrared radiation (an electromagnetic wave).
  • Emitting infrared radiation transfers thermal energy from the water to the cooler surroundings, decreasing the temperature of the water.
  • Darker/different coloured surfaces emit and absorb thermal radiation at different rates.

🧠 Quick Summary for Full Marks

  • Emitted wave type: Infrared (never ultraviolet or X-rays for cooling water!).
  • What is transferred: Energy (radiation transfers energy through electromagnetic waves).

Topics

Physics · P6: Waves

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 2 (Foundation), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.