Unit 8 · Thermal Physics

What Cambridge International AS & A Level Physics (9702) Unit 8 covers

Use this map to connect each assessed skill to the relationship or representation that makes it visible.

Thermal Physics

Connect the published share to the unit model

The gas state uses 1.10 × 10⁵ Pa, 2.40 × 10⁻³ m³ and 300 K. Absolute temperature is essential because pV = nRT is not a Celsius-scale relation.

The product pV equals 264 J, while RT equals 2493 J mol⁻¹. Their quotient gives 0.1059 mol before the final three-significant-figure statement.

A separate pressure–temperature plot holds the appropriate gas conditions fixed as shown by its equation. Reading its inverse curve requires attention to which quantity is placed on each axis.

Convert temperature to the required absolute scale before choosing an ideal-gas, kinetic, heating or first-law relation. Define the system and energy sign convention when heat or work is involved, then substitute compatible units. The numerical result should be followed by a statement of the process and the direction of energy transfer.

The decision that organizes this unit

Define the system and choose the route before calculating

Set pV = nRT

Mechanism route and repair branches

Relationships to preserve

• Gas state: Pressure, volume and temperature belong to one sample.
• Temperature: The supplied value is 300 K.
• Amount: 264 J is divided by 2493 J mol⁻¹.

Representations to read

• A graph of pressure (kPa) against temperature (K).
• A formula card that explains the ideal-gas relation balances pressure–volume energy with amount times rt.
• A table linking key concept, why it matters, visible method.

Branches to reject

• Substituting a Celsius value or omitting the volume prefix
• Treating the curve as p directly proportional to T
• Swapping temperature and pressure

How Cambridge International AS & A Level Physics (9702) assesses Thermal Physics

What a complete response must make visible

Match the task to evidence that a reader can audit, then check the most likely reasoning failure before finalizing the response.

Worked example: absolute temperature, ideal gases and energy transfer

Read each question as it appears on the exam paper, choose your answer, then tap it to see the feedback.

Practice 1: Amount of an ideal gas

Practice 2: Energy during a change of state

Key terms for Unit 8: Thermal Physics

Models, uses, and boundaries

Thermal Physics

The ideal-gas relation balances pressure–volume energy with amount times RT. Use this relationship when the ideal-gas relation balances pressure–volume energy with amount times RT..

Worked example: absolute temperature, ideal gases and energy transfer

Rearranging pV = nRT isolates moles after the joule units cancel. Use this relationship when rearranging pV = nRT isolates moles after the joule units cancel..

Thermal Physics: change one condition

The plotted temperatures of 325 K and 362 K lead to different pressures on the inverse curve. Use this relationship when the plotted temperatures of 325 K and 362 K lead to different pressures on the inverse curve..

Thermal Physics: test proposed results

Any proposed gas amount must use kelvin and preserve the 10⁻³ volume conversion. Use this relationship when any proposed gas amount must use kelvin and preserve the 10⁻³ volume conversion..

Cambridge International AS & A Level Physics (9702) Unit 8 FAQ

Evidence workshop

Continue from the free model into complete practice

The full unit guide continues with the chapter’s worked examples, figures, scoring tables, and answer checks.

• Worked example: absolute temperature, ideal gases and energy transfer
• Thermal Physics: change one condition
• Thermal Physics: test proposed results
• Check the worked-example evidence for Thermal Physics

Related Cambridge International AS & A Level Physics (9702) unit guides

How to study Cambridge International AS & A Level Physics (9702) Unit 8

Start with the organizing decision

Before solving, restate the decision in operational terms: Track joules on both sides of pV = nRT so that their cancellation leaves the amount of gas in moles.. Your first written move should be to Set pV = nRT.

Practice the same idea in several representations

Rotate through A graph of pressure (kPa) against temperature (K)., A formula card that explains the ideal-gas relation balances pressure–volume energy with amount times rt., A table linking key concept, why it matters, visible method.. Use each representation to practice Thermal Equilibrium and Temperature Scales (A Level), Specific Heat Capacity and Specific Latent Heat (A Level), The Mole and the Ideal Gas Equation of State (A Level), Kinetic Theory of Gases (A Level), Internal Energy and the First Law of Thermodynamics (A Level), and explain what stays invariant when the surface form changes.

Turn each error into a repair check

After every attempt, audit the response for Substituting a Celsius value or omitting the volume prefix; Treating the curve as p directly proportional to T; Swapping temperature and pressure. Then redo only the first step that made the reasoning diverge, keeping units, direction, and model conditions visible.

Confirm current course details in the official Cambridge International syllabus for the 2025-2027 administration.

Where to go next

Return to the Cambridge International AS & A Level Physics (9702) to see every unit and plan your revision.