What factors affect heat loss?

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By Daniel Ward

What factors affect heat loss?

PROBLEM

I have been asked to investigate the link between colour and heat loss. Does the silver or the black cup lose its heat faster?

HYPOTHESIS

I think that the silver cup will retain the heat for a longer period of time than the black cup, I think this because the black cup will absorb the heat, where as the silver cup will reflect the heat back into the cup causing the black cup to cool down faster than the silver cup.  

BACKGROUND INFORMATION

CONVECTION – the hot water in both cups will have convection current in them. The hot water will rise and sink as the water begins to cool. This means the heat energy is being passed on to the metal cup over most of its inner surface.

CONDUCTION – the metal cups will get hotter as a result of the heat energy inside the cup. The water will pass on this heat energy due to the fact that metal is a good conductor of heat. The heat energy will be conducted throughout the metal cup to the outer surface where it will be transferred to the air around the cup as radiation.

RADIATION – hot objects (i.e. the metal cup) emit mainly INFRARED radiation, and the hotter the object the more radiation it will emit. How much radiation the object emits will depend on the surface. The black cup had a dark matt surface and therefore will emit more radiation. This will mean that the black cup will lose more infrared radiation than the silver cup (which is a poor emitter of infra-red radiation) and as a result it will lose its heat quicker than the silver cup over the same amount of time.

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EQUIPMENT

  • Thermometer

  • Metal cups (silver and black)

  • Timer

METHOD

We started of with two cups one black and the other silver. Then we set up the apertures like the diagram above. We then got boiling water and poured it equally into each cup, then returned the lid. After the lid was replaced we recorded the temperature every 5 minutes.

SAFETY

To ensure ultimate safety during this test I have to take a few safety factors into ...

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