A student investigates heat loss from two identical beakers of hot water. Beaker X is wrapped in aluminium foil with the shiny side facing outwards. Beaker Y is wrapped in aluminium foil with the shiny side facing inwards. Both beakers are left in the same room. After 30 minutes, the temperature in beaker X is higher than in beaker Y.

What is the correct explanation for this observation?

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Question

A student investigates heat loss from two identical beakers of hot water. Beaker X is wrapped in aluminium foil with the shiny side facing outwards. Beaker Y is wrapped in aluminium foil with the shiny side facing inwards. Both beakers are left in the same room. After 30 minutes, the temperature in beaker X is higher than in beaker Y.

What is the correct explanation for this observation?

Accepted Answer

The shiny surface facing outwards in X is a poor emitter of infrared radiation — Award 1 mark for recognising that shiny surfaces are poor emitters of infrared radiation, reducing heat loss by radiation from beaker X. A is incorrect — reflecting room radiation would affect absorption, not emission from the beaker. C is incorrect — the orientation of the foil does not significantly affect conduction. D is incorrect — the foil orientation does not affect convection within the water.

Answer

The shiny surface facing inwards in Y increases convection currents in the water

Answer

The shiny surface facing outwards in X is a poor emitter of infrared radiation

Answer

The shiny surface facing outwards in X reflects room radiation back into the room

Answer

The shiny surface facing inwards in Y conducts heat faster to the surroundings

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