CIE iGCSE Co-ordinated Sciences-P2.3.1 Conduction- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-P2.3.1 Conduction – Study Notes
CIE iGCSE Co-ordinated Sciences-P2.3.1 Conduction – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Identify and give examples of typical good thermal conductors and bad thermal conductors (thermal insulators)
Supplement
- Describe thermal conduction in solids in terms of atomic or molecular lattice vibrations and also in terms of the movement of delocalised (mobile) electrons in metallic conductors
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Thermal Conductors and Insulators
Thermal Conductor: A material that allows heat to transfer through it quickly.
Thermal Insulator: A material that does not allow heat to pass through easily.
Explanation Using the Particle Model:
- In solids, heat is mainly transferred by vibrations of particles and the movement of free electrons (in metals).
- Good conductors (like metals) have many free electrons → transfer energy efficiently.
- Poor conductors/insulators (like wood or air) lack free electrons and have particles spaced further apart → heat transfer is slow.
Examples:
| Type | Examples | Explanation |
|---|---|---|
| Good Thermal Conductors | Copper, Aluminium, Iron | Metals with free electrons transfer heat quickly |
| Poor Thermal Conductors (Insulators) | Wood, Plastic, Glass, Air | No free electrons; particles farther apart → heat transfer slow |
Key Applications:
- Good conductors: saucepans, cooking utensils, radiators.
- Insulators: handles of saucepans (plastic/wood), house insulation (fiberglass, foam), thermos flasks.
Example :
Why is a metal spoon hot when left in a pot of boiling soup, but a wooden spoon is not?
▶️ Answer/Explanation
Step 1: Metals (like stainless steel) are good thermal conductors → heat energy is quickly transferred by free electrons from the soup to the spoon handle.
Step 2: Wood is a poor conductor (insulator) → it has no free electrons and transfers heat very slowly.
Final Answer: The metal spoon heats up quickly, while the wooden spoon remains cool.
Thermal Conduction in Solids
Thermal conduction is the transfer of heat energy through a solid without the bulk movement of the material. It occurs due to particle vibrations and, in metals, free electron movement.
1. Conduction by Lattice Vibrations (All Solids)
Atoms or molecules in a solid are held in a fixed lattice.
- When one part of the solid is heated, particles gain energy and vibrate more vigorously.
- These vibrations pass on energy to neighbouring particles through collisions.
- This process continues through the lattice, transferring heat across the solid.
- This mechanism is relatively slow, especially in non-metals.
2. Conduction by Free Electrons (Metals Only)
Metals have delocalised (mobile) electrons in addition to lattice vibrations.
- When heated, these electrons gain kinetic energy and move rapidly through the metal.
- They collide with atoms and other electrons, transferring energy efficiently.
- This makes metals much better thermal conductors than non-metals.
Comparison Between Metals and Non-Metals
| Material | Main Mechanism | Efficiency |
|---|---|---|
| Metals | Lattice vibrations + free electron movement | Very good conductors |
| Non-metals | Lattice vibrations only | Poor conductors (insulators) |
Key Concept:
- All solids conduct heat by lattice vibrations.
- Metals are far better conductors because they also have mobile electrons that spread energy quickly.
Example :
Why does a metal spoon heat up faster than a plastic spoon when placed in hot soup?
▶️ Answer/Explanation
Step 1: In metals, free electrons gain energy and move rapidly, transferring heat efficiently along the spoon.
Step 2: Plastic has no free electrons, so heat transfer occurs only by slow lattice vibrations.
Final Answer: The metal spoon conducts heat faster because of both electron movement and lattice vibrations, while the plastic spoon is a poor conductor.