2.3.1

Conduction

Cambridge IGCSE Physics (0625)  · Unit 2: Thermal physics  · 8 flashcards

Conduction is topic 2.3.1 in the Cambridge IGCSE Physics (0625) syllabus , positioned in Unit 2 — Thermal physics , alongside States of matter, Particle model and Gases and the absolute scale of temperature.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).

The deck below contains 8 flashcards — covering the precise wording mark schemes reward.

What the Cambridge 0625 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Describe Describe experiments to demonstrate the properties of good thermal conductors and bad thermal conductors (thermal insulators)
  2. Describe Describe thermal conduction in all solids in terms of atomic or molecular lattice vibrations and also in terms of the movement of free (delocalised) electrons in metallic conductors Supplement
  3. Describe Describe, in terms of particles, why thermal conduction is bad in gases and most liquids Supplement
  4. Know Know that there are many solids that conduct thermal energy better than thermal insulators but do so less well than good thermal conductors Supplement
Key Concept Flip

Describe an experiment to compare the thermal conductivity of a copper rod and a glass rod of the same dimensions. Include a labelled diagram and outline the key steps.

Answer Flip

1. Setup: Place one end of each rod into a beaker of boiling water. Attach thermometers at the other end of each rod, ensuring they are equidistant from the hot end.
2. Procedure: Record the initial temperature of each thermometer. Monitor the temperature increase of each thermometer over a fixed time period (

Example: 5 minutes).<br>3. <strong>Observation:</strong> The thermometer attached to the copper rod will show a higher temperature rise than the thermometer attached to the glass rod.<br>4. <strong>Conclusion:</strong> Copper is a better thermal conductor than glass because heat travels through it faster, resulting in a quicker temperature increase at the other end.<br>5. <strong>Diagram:</strong> (Not possible in text, but should include beakers of boiling water, rods inserted, thermometers attached at equal distances from the hot end, and labelled rods).
Key Concept Flip

State two properties that a good thermal conductor should possess.

Answer Flip

1. A good thermal conductor should allow heat to transfer through it quickly.
2. A good thermal conductor should have a low specific heat capacity, meaning it requires less energy to change its temperature.

Key Concept Flip

Describe how thermal energy is transferred through a solid metal rod via conduction at a microscopic level.

Answer Flip

Thermal conduction in metals occurs through two main mechanisms:

1. Atomic/Molecular Lattice Vibrations: When one end of the rod is heated, the atoms at that end vibrate more vigorously. These vibrations are passed on to neighboring atoms in the lattice, transferring thermal energy along the rod. The increased kinetic energy of atoms at the hot end is thus propagated as a wave of vibrations.

2. Movement of Free (Delocalised) Electrons: Metals contain many free electrons. These electrons gain kinetic energy from the heated end and move randomly throughout the metal lattice. As they move, they collide with atoms and ions in the lattice, transferring energy to them. This is a much faster and more efficient process than lattice vibrations alone, especially in good conductors.

Key Concept Flip

State how the process of thermal conduction differs in non-metallic solids compared to metallic solids at an atomic level.

Answer Flip

In non-metallic solids, thermal conduction primarily occurs through atomic or molecular lattice vibrations. Unlike metals, non-metallic solids have very few or no free (delocalized) electrons. Therefore, the dominant mechanism is the transfer of kinetic energy through vibrations of the atoms or molecules within the solid lattice. The rate of transfer is generally lower than in metals due to the absence of the free electron contribution.

Key Concept Flip

Explain, in terms of particles, why thermal conduction is generally poor in gases.

Answer Flip

Thermal conduction in gases is poor because the particles (atoms or molecules) are widely spaced. This means there are fewer collisions between particles to transfer kinetic energy (heat). The particles also move randomly and at lower speeds compared to solids, further reducing the rate of energy transfer. Therefore, the rate of transfer of thermal energy is slow.

Key Concept Flip

Describe the arrangement of particles and the intermolecular forces in a typical gas. How does this contribute to poor thermal conduction?

Answer Flip

In a gas, particles are widely spaced and move randomly. The intermolecular forces between gas particles are very weak or negligible. This arrangement leads to infrequent collisions between particles. Because the particles are far apart and don't interact strongly, the transfer of thermal energy (kinetic energy from particle to particle) through collisions is slow and inefficient, resulting in poor thermal conduction.

Key Concept Flip

Explain, in terms of particle behaviour, why copper conducts thermal energy better than wood, but not as well as silver.

Answer Flip

Copper has free electrons like silver, which can move through the structure and transfer thermal energy quickly. However, silver has a higher density of these free electrons and a more ordered crystal lattice structure, allowing for more efficient energy transfer. Wood, being a non-metal, has very few free electrons and a less ordered structure, making it a poor conductor of thermal energy.

Key Concept Flip

State two examples of solid materials that are better conductors of thermal energy than wool, but not as good as aluminium.

Answer Flip

1. Steel
2. Glass

These materials conduct heat more readily than wool because they have some free electrons or a more structured arrangement of atoms, allowing for easier energy transfer than wool's insulating air pockets, but not as efficiently as aluminium's highly mobile free electrons.

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2.2.3 Melting, boiling and evaporation 2.3.2 Convection

More topics in Unit 2 — Thermal physics

Conduction sits alongside these Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

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How to study this Conduction deck

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