Demonstrating Conduction

Conduction is the transfer of thermal energy through a material without the material moving. Imagine people standing in a line, each passing a small shake to the next person. The “shake” is energy moving from hot to cold.

What happens inside materials?

• Solids: Particles are packed closely. When one end is heated, particles vibrate more and pass this vibration along the solid.
• Metals: As well as vibrations, free (delocalised) electrons move and carry energy quickly. This makes metals very good conductors.
• Liquids and gases: Particles are farther apart, so they collide less often. This makes them poor conductors (they are better insulators).

Simple demonstrations

1. Metal vs wooden spoon
   • Method: Place a metal spoon and a wooden spoon with their bowls in hot water. Keep the handles out to test by touch (carefully).
   • Observation: The metal handle becomes hot quickly; the wooden handle stays cool longer.
   • Conclusion: Metal is a good conductor; wood is a poor conductor (insulator).
2. Wax and drawing pins on a metal bar
   • Method: Fix small pieces of wax along a metal bar and press drawing pins into each. Heat one end with a flame.
   • Observation: Pins drop off in order from the heated end to the cooler end.
   • Conclusion: Thermal energy travels through the bar from hot to cold.
3. Water conducts poorly
   • Method: Put ice at the bottom of a test tube (weighted so it stays down), fill with water, then gently heat near the top.
   • Observation: The top water can boil while the ice at the bottom remains solid.
   • Conclusion: Water is a poor conductor; heat does not pass down quickly by conduction.

Fair test and safety

• Use equal-sized rods/spoons, same starting temperature, and equal heating distance/time.
• Wear eye protection and use tongs; do not touch hot metal.

Everyday links

• Saucepans: metal bases conduct heat to food; plastic or wooden handles reduce burns.
• Clothing and double glazing trap air, which is a poor conductor.

Common misconceptions

• “Heat rises” describes convection, not conduction. Conduction works in any direction through contact.
• Metal does not “make things cold”; it conducts your body’s heat away faster, so it feels colder.