Which materials carry heat
Chemistry · Key Stage 2 · The School
Stand a metal spoon and a wooden spoon in the same mug of hot water and come back in two minutes. The metal handle is warm and the wooden one is not. The water gave heat to both; only one carried it up to your fingers. That difference is thermal conductivity, and it is a property you measure rather than guess.
Use rods of the same length and thickness, start them at room temperature, put the same end of each into water at the same temperature, and read them at the same moment. If one rod is thicker or starts warmer, the result tells you about the thickness or the head start, not about the material.
Copper, aluminium and steel carry heat quickly. Wood, plastic, glass and air are poor conductors, which is another way of saying they are good insulators. A material is not good or bad here — it is suited to keeping heat moving or to holding it still, and the job decides which you want.
A coat does not make heat. It slows the heat leaving you, because the fibres hold still air and air conducts badly. This is also why two thin layers beat one thick one: the gap between them traps more air. The insulator doing the work is mostly the air, not the fabric.
A hand is a poor thermometer, because it reports how fast heat is leaving it rather than how hot something is. Tape a thermometer to the far end of each rod and read the temperature every minute for five minutes. Now the comparison is a set of numbers two people would agree on, and you can draw the results as a line for each material and see which climbed fastest.