G3 Physics and O-Level Thermal Physics Hub
G3 Physics and O-Level Thermal Physics hub covering the particle model, thermal processes, internal energy, heat capacity, changes of state, latent heat and cooling curves.
Learning goals
- Compare physical properties of solids, liquids and gases
- Explain state properties using particle arrangement, motion, forces and separation
- Infer random molecular motion from a Brownian-motion experiment
- Relate temperature rise to increased average kinetic energy of particles
- Explain gas pressure using particle collisions with container walls
- Explain heating from higher to lower temperature until thermal equilibrium
- Describe conduction in solids through particle vibration and mobile electrons
- Describe convection in fluids through density changes and bulk motion
- Explain that energy transfer by electromagnetic radiation needs no material medium
- Explain how surface colour, texture, temperature and area affect radiation transfer rate
- Apply conduction, convection and radiation in everyday systems
- describe internal energy as an energy store that is made up of the total kinetic energy associated with the random motion of the particles and the total potential energy between the particles in the system
- Define heat capacity and specific heat capacity
- Apply energy transferred = mass × specific heat capacity × temperature change
- describe melting/solidification and boiling/condensation as processes of energy transfer without a change in temperature
- Explain the difference between boiling and evaporation
- Define latent heat and specific latent heat
- Apply energy transferred for a change of state = mass × specific latent heat
- Explain latent heat using particle behaviour
- Sketch and interpret a cooling curve
Thermal Physics uses a microscopic particle model to explain observations such as state, temperature, gas pressure, energy transfer and changes of state.
Prerequisites: revise energy stores and transfers, density, and graph axes and gradients from core exam skills.
Recommended core path:
- Particle model, Brownian motion and gas pressure
- Internal energy and temperature
- Thermal equilibrium
- Conduction, convection, then radiation
- Heat capacity and specific heat capacity
- Melting and solidification and boiling, condensation and evaporation
- Specific latent heat, then cooling curves
Use the Kinetic Model and Gas Pressure Explorer after step 1 and the Thermal Physics Explorer after step 4.
What you will learn
Begin with the particle model because it supplies the reasoning used later for thermal processes, internal energy and changes of state. The final lessons combine those ideas when you interpret cooling curves.
Topic 7: Kinetic particle model of matter
- States and properties: compare solids, liquids and gases, then explain their properties using particle arrangement, motion, forces and separation. → Kinetic particle model
- Brownian evidence: distinguish the visible suspended particle from the unseen molecules whose random impacts are inferred. → Kinetic particle model
- Temperature and gas pressure: relate a temperature rise to greater average particle kinetic energy and explain gas pressure through wall collisions. → Kinetic particle model
Topic 8: Thermal processes
- Heating and equilibrium: energy transfers from higher to lower temperature until thermal equilibrium. → Thermal equilibrium
- Conduction: describe particle-vibration transfer in solids and the additional mobile-electron mechanism in metals. → Conduction
- Convection: explain bulk fluid motion through temperature-dependent density changes. → Convection
- Radiation and applications: explain why electromagnetic radiation needs no medium; use surface colour and texture, temperature and area; apply all three processes in everyday systems. → Radiation, conduction, convection
Topic 9: Thermal properties of matter
- Internal energy: total random kinetic energy plus total potential energy of particles. → Internal energy
- Heat capacity: define heat capacity and specific heat capacity and apply Q = mcΔθ. → Heat capacity
- Changes of state: describe melting, solidification, boiling and condensation at constant temperature; distinguish boiling from evaporation. → Melting and solidification, boiling, condensation and evaporation
- Latent heat: define latent heat and specific latent heat, apply Q = ml, and explain the particle-energy change. → Specific latent heat
- Cooling curves: sketch and interpret states, slopes and constant-temperature plateaux. → Cooling curves
Laboratory thermometer technique prepares you to measure temperature in Paper 3 practical work.
Lessons
Kinetic model and temperature
Kinetic Particle Model
States and properties, Brownian-motion evidence, temperature and gas pressure.
Internal Energy
Internal energy is total random kinetic energy plus particle potential energy.
Thermal Equilibrium
Net energy transfer by heating stops at equal temperatures.
Thermal processes
Conduction
Particle vibrations in solids and the additional mobile-electron mechanism in metals.
Convection
Density differences drive bulk fluid circulation.
Radiation
Transfer without a medium; surface finish, temperature and area factors.
Thermal properties and calculations
Specific Heat Capacity
Calculating energy for temperature change (Q = mcΔθ).
Melting & Solidification
Constant-temperature changes between solid and liquid, linked to particle energy.
Boiling vs Evaporation
Boiling and condensation at constant temperature; evaporation at the surface.
Latent Heat
Calculating energy for state change (Q = ml).
Cooling Curves
Sketching and interpreting states, slopes and constant-temperature plateaux.
Practical skills
Laboratory Thermometer
Paper 3 practical technique: range, resolution, immersion and equilibrium.
Calorimetry Practical
Measure V, I, t, m and temperature rise; evaluate heat-loss bias.
Applications
Insulation and trapped air
Why air gaps reduce conduction; why foam is effective.
Sea breeze and refrigerators
Convection currents from density differences in fluids.
Vacuum flask and shiny surfaces
How shiny surfaces reduce radiation; vacuum reduces conduction/convection.
Beyond the syllabus
Thermometric Properties
Fixed-point interpolation and calibration reasoning.
Revision
| Decision | Relationship | What changes microscopically? |
|---|---|---|
| Temperature changes, no state change | Q = mcΔθ | Average kinetic energy changes |
| State changes at constant temperature | Q = ml | Particle arrangement and potential energy change |
| Two regions have different temperatures | Energy transfers from higher to lower temperature | Transfer continues until thermal equilibrium |
Common exam traps
- Temperature is not internal energy. Temperature relates to average particle kinetic energy; internal energy is a total microscopic store.
- A plateau does not mean no energy transfer. Latent energy changes particle potential energy while temperature stays constant.
- Use the temperature change. In Q = mcΔθ, calculate final minus initial temperature and convert mass to kilograms.
- Do not write “heat rises”. For convection, state expansion, lower density, rising fluid and cooler replacement flow.
- A vacuum does not stop radiation. It suppresses conduction and convection; silvered surfaces reduce radiation.
- Brownian motion is an inference question. You observe the suspended particle and infer random motion of unseen molecules.
- Boiling is not evaporation. Boiling occurs throughout at a fixed temperature; evaporation occurs at the surface at any temperature.
Practice
- Start with the Thermal Physics topic check to find the first idea to revisit.
- Check recall and quick calculations in the Thermal Physics quiz.
- Show full explanations and working in structured Thermal Physics practice.
- Use the Thermal Physics Explorer to compare transfer processes and interpret heating and cooling curves.
Continue learning
Continue to Waves. Thermal radiation provides the bridge: it transfers energy as electromagnetic waves and is revisited in the electromagnetic spectrum. Return to the Pressure hub if density or gas-pressure foundations need revision.
For material beyond O-Level, the A-Level Thermal Physics hub introduces ideal gases and thermodynamics.
Continue with the next resource in this course.
Course and syllabus information
- Course
- SEC G3 Physics
- Edition
- SEC G3 Physics 2027