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EnglandCombined Science

Edexcel GCSE Combined Science CP14 Particle model: a complete overview of density, internal energy and changes of state

A deep-dive Edexcel GCSE Combined Science guide to Topic 14 (CP14) Particle model. Covers the particle model and the states of matter, the density equation, internal energy, specific heat capacity, changes of state and specific latent heat, with the core practical and exam patterns Edexcel repeats.

Generated by Claude Opus 4.812 min readCP14

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section
  1. What CP14 actually demands
  2. The particle model and density
  3. Internal energy and heating
  4. Changes of state
  5. How CP14 is examined
  6. Check your knowledge

What CP14 actually demands

The particle model, on Physics Paper 2, links the arrangement of particles to density and to the energy changes during heating and changes of state. The examiners reward the density calculation and a clear particle-model explanation of why temperature stays constant during a change of state.

This guide walks through the topic and ties together the matching dot-point page, which has its own practice questions.

The particle model and density

In the particle model, solids have fixed, vibrating particles, liquids have close particles that move past each other, and gases have far-apart, fast particles. Density is mass per unit volume:

ρ=mV\rho = \frac{m}{V}

Solids are usually densest and gases least dense.

Internal energy and heating

Internal energy is the total kinetic and potential energy of the particles. Heating either raises the temperature (specific heat capacity, the energy to raise 1 kg1\,kg by 1 ∘C1\,^{\circ}C) or changes the state (specific latent heat) at constant temperature.

Changes of state

During a change of state the temperature stays constant, because the energy breaks the forces between particles rather than raising their kinetic energy. Changes of state are physical and reversible, and mass is conserved.

How CP14 is examined

  • Calculations. Finding density from mass and volume.
  • Particle model. Explaining density and changes of state from the particle arrangement.
  • Energy. Distinguishing specific heat capacity and specific latent heat.
  • Graphs. Explaining the flat sections of a heating curve as changes of state.

Check your knowledge

A mix of recall and calculation questions covering CP14. Attempt them under timed conditions, then check against the solutions.

  1. State the equation for density. (1 mark)
  2. A block has a mass of 400 g and a volume of 50 cm3. Calculate its density. (2 marks)
  3. Which state of matter is usually the densest? (1 mark)
  4. Define internal energy. (1 mark)
  5. Define specific heat capacity. (2 marks)
  6. Why does the temperature stay constant during melting? (2 marks)
  7. Define specific latent heat. (1 mark)
  8. Are changes of state physical or chemical? (1 mark)

Sources & how we know this

  • combined-science
  • gcse-edexcel
  • edexcel-physics
  • particle-model
  • density
  • internal-energy
  • specific-heat-capacity
  • latent-heat