AQA GCSE Physics Physics Paper 1 (Higher), June 2022: Question 8
11 marks · Standard Demand difficulty · Short Answer
Determine the specific latent heat of vaporisation of water using experimental data, identify hazards and equipment, and explain the effects of thermal energy transfer and early evaporation on results.
Practise this questionQuestion
Question text
08 A student determined the specific latent heat of vaporisation of water.
Figure 9 shows some of the equipment used.
Figure 9
This is the method used:
1. Put 50 cm3 of water in a beaker.
2. Measure the mass of the beaker and water.
3. Use a heater to boil the water and keep it boiling for 600 seconds.
4. Measure the mass of the beaker and water after 600 seconds.
08.1 What measuring instrument should be used to measure the volume of water?
[1 mark]
08.2 What is a hazard in the student’s investigation?
[1 mark]
Tick ( ) one box.
burns
boiling water
heatproof gloves
safety goggles 23
08.3 The initial mass of the beaker and water was 0.080 kg.
The final mass of the beaker and water was 0.071 kg.
*22* The energy transferred by the immersion heater as the water boiled was 25 200 J.
Calculate the specific latent heat of vaporisation of water given by the student’s data.
Give the unit.
Use the Physics Equations Sheet.
[5 marks]
Specific latent heat of vaporisation = Unit
08.4 Some thermal energy was transferred to the surroundings while the water was
being heated.
Explain how this affected the student’s value for the specific latent heat of vaporisation
of water.
[2 marks]
08.5 Some of the water evaporated before its temperature reached 100 °C.
Explain how this affected the student’s value for the specific latent heat of vaporisation
of water.
*23* [2 marks]
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
08.1 measuring cylinder allow burette 1 AO3
allow beaker with scale / 4.3.2.3
graduations
AO /
Spec. Ref.
08.2 boiling water 1 AO3
4.3.2.3
AO /
Spec. Ref.
08.3 change in mass = 0.009 (kg) 1 AO2
25 200 = 0.009 L allow a correct substitution using 1 AO2
an incorrectly calculated value
of m
AO2
25 200 allow a correct rearrangement 1
L = using an incorrectly calculated
0.009
value of m AO2
L = 2.8 × 106 allow a correctly calculated 1
or answer using an incorrectly AO1
L = 2 800 000 calculated value of m
4.3.2.3
J/kg if a unit other than J/kg is given 1
it must match the numerical
answer – HYSICS – –
AO /
Spec. Ref.
08.4 less energy (than 25 200 J) was 1 AO3
transferred to the water 4.3.2.3
(so) student’s value of L was too 2nd mark conditional on scoring 1
high 1st mark
AO /
Spec. Ref.
08.5 the measured change in mass is allow a smaller mass of water 1 AO3
too high (for the energy actually changed state at boiling 4.3.2.3
supplied) point
(so) student’s value of L is too 2nd mark conditional on scoring 1
low 1st mark
– HYSICS – –
Total Question 8 11
Question 9
How to answer it
Determining Specific Latent Heat of Vapourisation
What this question tests
This question assesses your ability to recall standard laboratory equipment, identify experimental hazards, perform multi-step calculations using the specific latent heat equation ( E = m × L ), and critically evaluate how thermal energy losses and premature evaporation affect experimental results.
Measuring Volume
✅ Correct Answer
measuring cylinder
1 mark available (AO3)
💡 Key Knowledge
- A measuring cylinder is designed to accurately measure liquid volumes in millilitres ( cm³ ).
- Beakers have scale markings, but they are only for rough estimation, not precise measurements.
Identifying Hazards
✅ Correct Answer
boiling water
1 mark available (AO3)
❌ Common Errors
Students frequently confuse hazards (the source of potential harm, like boiling water or hot heaters) with safety precautions (items used to mitigate risk, like safety goggles or heatproof gloves).
Calculation of Specific Latent Heat
📐 Step-by-Step Calculation
- Find mass of water evaporated ( m ):
Initial mass - Final mass = 0.080 kg - 0.071 kg = 0.009 kg - Recall the formula:
E = m × L rearranged to L = E / m - Substitute values:
L = 25200 / 0.009 - Calculate final answer:
2,800,000 J/kg or 2.8 × 10⁶ J/kg
5 marks available (AO1 / AO2)
🧠 Exam Technique & Units
- Unit required: J/kg (Joules per kilogram).
- Method marks are awarded sequentially. Even if you make an arithmetic error calculating the mass change, you can still pick up subsequent marks by carrying your incorrect mass forward correctly.
Evaluating Thermal Energy Losses
✅ Correct Answer
- Less energy than supplied ( 25200 J ) was actually transferred to the water because some escaped to the surroundings.
- Therefore, the calculated value of L was too high.
2 marks available (AO3) - Note: The second mark is conditional on scoring the first.
🧠 Examiner Insight
To link energy loss to the final calculated value, reason through the formula: L = E / m . If the effective energy ( E ) heating the water is actually smaller than measured, but you divide by the full mass, your mathematical output becomes artificially inflated.
Evaluating Premature Evaporation
✅ Correct Answer
- The measured change in mass was too high for the energy supplied (because water evaporated before reaching 100 °C ).
- Therefore, the student's value for L was too low.
2 marks available (AO3) - Note: Second mark is conditional on the first.
💡 Key Knowledge
Latent heat calculations assume all energy is used exclusively to change state at boiling point. If water evaporates beforehand, mass is lost without accounting for the extra heat required, making the resulting latent heat calculation an underestimate.
Topics
Physics · P3: Particle Model of Matter
Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 1 (Higher), June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.