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Thermal Energy Transfer: Question 1

Syllabus 2.3.1

Multiple choice Core 1 mark

A school science technician is comparing how well four flat tiles of different material conduct thermal energy: copper, steel, glass and expanded polystyrene foam. Each tile is identical in size and thickness. An electric heating pad, set to the same power on every tile, is stuck to the centre of the underside of each tile, and a small thermometer probe is fixed to the top surface exactly 5 cm5\text{ cm} from the centre. All four heaters are switched on at the same moment. Exactly 44 minutes later, the technician reads the temperature rise shown by each surface probe:

Tile material Temperature rise after 4 minutes
Copper 38 °C38\text{ °C}
Steel 21 °C21\text{ °C}
Glass 4 °C4\text{ °C}
Expanded polystyrene foam 1 °C1\text{ °C}

Based on these results, which tile material is the best thermal conductor?

Choose an answer to check it, then compare with the worked solution below.
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Worked solution

Step 1: Understand what the experiment measures

Every tile is the same size and thickness, heated by an identical heating pad for the same time, with a thermometer probe at the same distance from the heater. The only thing that differs between the four tiles is the material. So any difference in the temperature rise recorded at the probe must be caused by how quickly each material conducts thermal energy from the heater to the probe.

  • A material that conducts thermal energy quickly carries more energy out to the probe within the fixed 4 minutes, so the probe reads a large temperature rise.
  • A material that conducts thermal energy poorly (an insulator) lets very little energy reach the probe in that time, so the probe reads a small temperature rise.

So the largest temperature rise identifies the best thermal conductor.

Step 3: Compare the recorded values

Tile materialTemperature rise after 4 minutes
Copper38 °C38\text{ °C}
Steel21 °C21\text{ °C}
Glass4 °C4\text{ °C}
Expanded polystyrene foam1 °C1\text{ °C}

Copper’s probe recorded the largest rise, 38 °C38\text{ °C}, so copper conducted thermal energy to the probe fastest.

Step 4: Match to the correct option

Copper is the best thermal conductor of the four materials tested. This is option A.

Why the other options are wrong

OptionMaterialWhy it doesn’t fit
BSteelIts temperature rise (21 °C21\text{ °C}) was much smaller than copper’s, so steel conducts less well than copper.
CGlassIts temperature rise (4 °C4\text{ °C}) was far smaller than either metal’s, showing glass is a poor conductor by comparison.
DExpanded polystyrene foamIts temperature rise was the smallest of all (1 °C1\text{ °C}), showing it is a thermal insulator, not a good conductor.

Final answers

  • Copper is the best thermal conductor, option A.