AQA GCSE Physics Physics Paper 1 (Higher), June 2025: Question 2

Determining the Specific Heat Capacity of Water

📋 What This Question Tests

This question assesses core skills from AQA Required Practical 1 (Specific Heat Capacity): identifying laboratory hazards, writing a logical step-by-step scientific method, evaluating experimental errors and improvements, and calculating percentage difference using standard experimental data.

Part 02.1 · 1 Mark

Lab Safety & Hazards

Identify a hazard in the investigation

✅ Acceptable Answers

Hot water or hot beaker
Heater (it gets very hot)
Also allowed: Spilt water (slipping hazard) or broken glass / beaker

❌ Common Errors & Examiner Trap

Do not confuse a hazard with a risk:

A hazard is the object or situation with potential to cause harm (e.g. hot heater, hot water).
A risk is the actual harm or injury (e.g. burns to skin). The mark scheme states: "ignore descriptions of risk". Writing just "getting burnt" scores 0.

Mark Breakdown: 1 mark for naming any valid hazard (heater, hot water, broken glass, spilt water).

Part 02.2 · 6 Marks

Extended Response: Experimental Method

Describe how to determine the specific heat capacity of water using the provided apparatus

💡 Governing Equation

The entire method must provide values for every variable in:

ΔE = m × c × Δθ

Rearranged to find specific heat capacity ( c ):

c = ΔE / (m × Δθ)

ΔE = energy transferred (measured by joulemeter)
m = mass of water (measured using the balance)
Δθ = temperature change (measured with thermometer)

🧠 Level 3 Marking Criteria (5–6 Marks)

To hit the top band, your answer must be a coherent, logically ordered method that would produce a valid outcome:

Mandatory: You must explain clearly how the mass of the water is measured (not just the beaker!).
Every piece of equipment from Figure 4 must have a clear purpose.

✅ Model 6-Mark Method

Find mass of water: Place the empty beaker on the balance and record its mass. Pour water into the beaker and record the total mass. Subtract the empty beaker mass from the total mass to find the mass of water ( m ). (Alternative: Place empty beaker on balance and press tare / zero before adding water.)
Initial temperature: Place the thermometer into the water and record the starting temperature.
Setup & Heat: Submerge the immersion heater fully in the water and note the initial reading on the joulemeter (or reset it to zero). Turn on the power supply to heat the water.
Final readings: After a suitable temperature rise, switch off the power supply. Stir gently and record the highest final temperature reached on the thermometer.
Energy reading: Read and record the total energy transferred ( ΔE ) shown on the joulemeter.
Calculation: Calculate temperature change ( Δθ = final temp - initial temp ), then calculate specific heat capacity using the formula c = ΔE / (m × Δθ) .

❌ Why Students Lost Marks

Vague mass measurement: Simply writing "weigh the beaker" without stating how the mass of the water alone is obtained caps the answer at Level 2 (max 4 marks).
Omitting the calculation: Forgetting to state how the recorded values are processed into a final value of specific heat capacity.
Using stopwatches: Some students described measuring time and calculating power, ignoring the fact that a joulemeter is already present in Figure 4 to measure energy directly!

Mark Breakdown: Level 3 (5–6 marks) requires all key steps logically ordered, explicitly detailing how the mass of water is determined and how specific heat capacity is calculated.

Part 02.3 · 1 Mark

Reducing Systematic Experimental Error

Suggest one change to the apparatus to reduce energy loss to the surroundings

✅ Acceptable Answers (Any 1)

Insulate the beaker (e.g. wrap beaker in bubble wrap, felt, or foam).
Add an insulating lid to reduce energy lost via convection and evaporation.
Replace the glass beaker with an insulating cup (e.g. a polystyrene / plastic cup).

❌ Common Errors

Writing "repeat and calculate an average" — repeating does not reduce heat loss to the room; heat loss is a systematic error, not a random one.
Saying "use more water" or "turn the heater up higher" — these do not stop energy dissipating into the surrounding air.

Mark Breakdown: 1 mark for mentioning insulation around the beaker, an insulating cup, or adding a lid.

Part 02.4 · 2 Marks

Percentage Difference Calculation

Calculate the percentage difference between the student's value (4410 J/kg °C) and the actual value (4200 J/kg °C)

📐 Step-by-Step Calculation

1 Find absolute difference:

Difference = 4410 - 4200 = 210 J/kg °C

2 Divide by the actual (true) value:

210 / 4200 = 0.05

3 Multiply by 100 to get a percentage:

0.05 × 100 = 5%

Final Answer: 5 %

❌ Calculation Traps & Examiner Warning

Dividing by the wrong number: Many students divided by the student's experimental value (4410) instead of the accepted reference value (4200):
(210 / 4410) × 100 = 4.76%.
The mark scheme explicitly states: do not accept 4.76 (%). Percentage differences / errors must be calculated relative to the actual / true value!

Mark Breakdown:
• Mark 1: Correct difference calculated ( 210 ) OR full substituted fraction [(4410 - 4200) / 4200] × 100 .
• Mark 2: Correct final answer of 5 (or 5% ).