Particle model
Lesson overview
This lesson introduces the core physics idea, the useful equipment and the calculation or data skills used on this page.
What you will learn
Heating data supplied on this page
Use water, metal block and melting examples to practise choosing between temperature-change and change-of-state equations.
Specific heat capacity and latent heat infographic
Clear explanation
Specific heat capacity tells you how much energy is needed to raise 1 kg of a substance by 1 degree Celsius.
Specific latent heat tells you how much energy is needed to change the state of 1 kg of a substance without changing temperature.
The key decision is whether temperature changes. If temperature changes, use the specific heat capacity equation. If state changes at constant temperature, use latent heat.
Key graph
Worked examples
Heating water
2 kg of water is heated by 10 degrees Celsius. The specific heat capacity is 4200 J/kg degrees Celsius.
energy = mass x specific heat capacity x temperature change
energy = 2 x 4200 x 10 = 84 000
Quick checks
Choose an answer, then check your thinking.
1. Which equation is used when temperature changes but state does not?
2. What happens to temperature during melting at the melting point?
Practice questions
Question 1
A 0.5 kg block with specific heat capacity 900 J/kg degrees Celsius warms by 20 degrees Celsius. Calculate energy transferred.
Reveal answer and marking guidance
Answer: 9000 J.
Marking: Credit E = m c delta theta = 0.5 x 900 x 20 = 9000 J.
Question 2
Calculate energy needed to melt 0.2 kg of a substance with latent heat 100 000 J/kg.
Reveal answer and marking guidance
Answer: 20 000 J.
Marking: Credit E = m L = 0.2 x 100 000 = 20 000 J.
Question 3
Why is latent heat not calculated using temperature change?
Reveal answer and marking guidance
Answer: During a change of state, temperature stays constant while energy changes particle arrangement.
Marking: Credit state change and constant temperature.
Question 4
On a heating graph, what does a flat section usually show?
Reveal answer and marking guidance
Answer: A change of state.
Marking: Credit melting or boiling at constant temperature.
Practice ladder
Answers and marking guidance
The exact practice answers are hidden under each question so you can try first. For this lesson, marks come from using the correct physics model, choosing the right equation where needed, keeping units with values, and explaining changes with precise words such as transfer, resultant force, acceleration, evidence and uncertainty.
Common mistakes
- Using latent heat when temperature changes.
- Forgetting mass must be in kg for standard units.
- Treating degrees Celsius as the energy unit.
- Ignoring flat sections of heating graphs.
Extension challenge
Write two heating questions with the same mass, one using specific heat capacity and one using latent heat.
Reveal answer
Example answer: A strong extension response names the physics model, uses accurate units and explains why the evidence supports the conclusion.
Exam-board guidance
Short board notes only. Learn the core physics above first.
AQA GCSE Physics
AQA GCSE Physics: often rewards clear physics explanations, correct equations, units and practical evidence for specific heat capacity and specific latent heat.
OCR GCSE Physics
OCR GCSE Physics: often values precise definitions, clear working, graph interpretation and links between models and evidence.
Pearson Edexcel GCSE Physics
Pearson Edexcel GCSE Physics: often combines the concept with equation use, data handling and practical interpretation.
Eduqas GCSE Physics
Eduqas GCSE Physics: learn the core explanation and practise applying it to unfamiliar contexts, data and practical questions.
WJEC Wales
WJEC Wales: often expects accurate terms, units and evidence-based explanations using the shared physics idea.
CCEA GCSE Physics
CCEA GCSE Physics: connect the idea to your current unit and use the same practical method language your class uses.
Next lesson
Next, continue with Distance-Time and Velocity-Time Graphs.