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Science and biology

KS23. Place your hand in a polythene bag for about 10 minutes and it will feel clammy. Then test the inside of the bag with cobalt chloride paper to show that this has been caused by water. You can use this indicator paper to find out which part of the exposed skin produced the most sweat in a certain amount of time. Check for allergies before you tape the paper to the skin and then time how long it takes for the paper to turn pink, indicating the presence of water or sweat.

Test which part of the body is most and least sensitive to touch. The relative nature of heat-sensitivity can be shown using three bowls of water: one warm, one cold and one hot. Put the right hand in the hot bowl and the left in the cold. Leave them for about 30 seconds and then put both hands in the warm bowl. The right hand will feel cold and the left one hot.

KS34: Use four thermometers to show how the evaporation of sweat causes the body to cool. The first one should be untouched. Wrap the second in dry muslin and the third in muslin damp with alcohol (a substitute for aftershave). The fourth should be wrapped in muslin soaked with alcohol.

Which one cools the fastest?

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