Particle model: GCSE Combined Science
Density, the density required practical, internal energy and specific heat capacity, latent heat, particle motion and pressure in gases
The short version
Use ρ = m/V, describe the density practical, use ΔE = mcΔθ and E = mL, and explain gas pressure with particle collisions.
Key idea
Density in kg/m^3 or g/cm^3; mass in kg or g; volume in m^3 or cm^3
Grade 2–3: Density is how packed the mass is. Stones sink; ice cubes float.
Grade 5–6: I can use rho = m/V and V = l x w x h for a cuboid. Water is about 1000 kg/m^3 or 1.0 g/cm^3.
Grade 9: 1 g/cm^3 = 1000 kg/m^3. 1 m^3 = 1 000 000 cm^3. Solids are usually densest (particles close). Gases have large gaps. If they give mass and dimensions, volume first - that working is often a mark on its own.
Go a bit deeper
Liquids have similar spacing to solids but are disordered. Heating a gas at constant pressure makes it expand - density falls. When ice melts, mass is conserved but the liquid volume is smaller than the ice, so density rises.
Worked example
Worked example
Grade 2–3: Density is how packed the mass is. Stones sink; ice cubes float. Grade 5–6: I can use rho = m/V and V = l x w x h for a cuboid. Water is about 1000 kg/m^3 or 1.0 g/cm^3. Grade 9: 1 g/cm^3 = 1000 kg/m^3. 1 m^3 = 1 000 000 cm^3. Solids are usually densest (particles close). Gases have large gaps. If they give mass and dimensions, volume first - that working is often a mark on its own.
Lessons in this topic
- Density
- Density required practical
- Internal energy SHC
- Specific latent heat Combined
- Particle motion gases
- Pressure in gases Combined
In the app each lesson is video (when we have a real YouTube id) then intro, learn and summary steps.
What the examiner wants
Convert units before density calculations. SHC is energy to raise 1 kg by 1 °C; latent heat is energy to change state at constant temperature. pV = constant is Higher.
Try these questions
Cover the answers and have a go first. Worked solutions are underneath.
Density is
A 400 g object has volume 80 cm³. Density is
1.0 g/cm³ is the same as
Volume of an irregular stone is best found with
Common mistakes
- Do not mix cm and m in one calculation. 1 m^3 is not 100 cm^3.
- The object must be fully submerged. If it floats, Combined usually still expects you to say push it under or use a sinker - do not invent a volume from a floating waterline.
- Do not use the final temperature as Δθ. Mass must be in kg if c is in J/kg°C.
- Do not say bonds in molecules are broken when ice melts. You are overcoming attractions between particles, not splitting H2O into H and O.
Answers and working
Frequently asked questions
Is GCSE Particle model on Combined Science and Triple?
Particle model is on Combined Science and on Triple Physics. Progress is shared in the ReviseEasy app.
Which exam board is this Particle model page for?
The ideas are board-agnostic for AQA, Edexcel, OCR, WJEC and CCEA. Paper lengths and question numbers differ — check your specification.
Is Particle model Foundation or Higher?
The core ideas appear on both tiers. Higher papers add extra application and some HT-only detail, marked in lessons with a Higher badge.
Learn, try, get feedback, fix the mistake
Open the stepped lesson, then the quiz with hints. Required-practical and calculation questions use the same method you will need in the paper.
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