Which material conducts heat best? The wax bead race
Stand rods of copper, aluminium, iron, glass and wood in hot water with wax beads stuck along them, and watch how fast the heat travels.
Core concept
Metals are good conductors of heat; glass and wood are poor conductors (insulators)
Topic: Heat
Conduction is the way heat travels through a solid. Where the solid is heated, its particle: A tiny piece that matter is made of, far too small to see. All key words vibrate faster and pass the energy: What is needed to make things move, heat up, light up or grow. All key words to their neighbours, all along the material. In metals, free electrons carry the energy quickly, so metals are good conductor: A material that lets electricity or heat pass through easily, like copper. All key words. Materials like glass, wood and plastic pass heat on very slowly; they are poor conductors, or insulator: A material that does not let electricity or heat pass through easily, like plastic. All key words. Wax beads stuck along a rod melt and drop off as the heat reaches them, showing how fast the heat travels.
What you will learn
- Describe conduction as heat passing from particle to particle.
- Rank materials from the best to the worst conductor of heat.
- Give uses of good conductors and insulators.
Before you start
- Know that wax melts when it is heated.
Materials
- Rods of copper, aluminium, iron, glass and wood of the same size
- Wax beads (candle wax)
Equipment
- Beaker of hot water
- Stopwatch
Procedure
- Choose the copper rod and move the time slider to 30 s, 60 s and 120 s. Record how many beads have fallen.
- Repeat with iron and glass, recording each at 120 s.
- Compare the rods and rank them.
How this simulation is simplified
- The rods are long and lose no heat to the air; the hot water stays at 100 °C and the room at 25 °C.
- Wax melts at 50 °C. Each material spreads heat at its own fixed rate (its thermal diffusivity).