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Practicals

Thermal Insulation
AKA: Conduction Cans

Summary

Metal cans, covered in different insulating materials are filled with boiling water. An inserted thermometer records the temperature of the cooling water, proving that the more insulated cans retain heat for longer.

Operation

As a demonstration, a series of about five cans would give good results, although teachers may specify a larger or smaller number depending upon how accurately they would like resultant data. Some teachers like to do this experiment as a class set, therefore a lot of preparation may be required. Some may just like to have the raw materials so pupils can set up their own experiment.

In this practical, boiling water (from kettles) is poured in equal amounts into the cans. Lids and thermometers are placed on the cans and a stopwatch is started. Pupils can record the temperatures at regular intervals (eg 20s). The water inside the cans will cool down at different rates depending upon how insulated the can is. As a rule, the more air that is trapped in the insulating material, the better the insulation. Cans covered in more indulation material will cool significantly slower than cans with little or no insulation. Because students may rush the pouring of the water to get all the cans started at the same time, students may be asked to start the timer once the temperature of each can has fallen to a certain level, for example 70 degrees. This makes the practical safer and also makes for a fairer test.

Regular sized empty food cans are perfect for this, just remove the labels and file down any sharp edges. One can in the set may be the 'control' so no covering is necessary. For the others, a layer of either corrugated cardboard, bubblewrap, polystyrene, foam, felt, carpet, foil etc may be suitable. Layers are easily held to the can with rubber bands. Leave the open top of the can open. Lids can be simply made from either squares of polystyrene foam or thick card with a hole in the middle for the thermometer.

This practical can be conducted in one of two ways, either by using different types of insulating material on each can or have one material such as bubblewrap and varying the amount of layers used on each can.

Stopwatches and kettles may also be required, amounts will depend on the size of the sets of cans.

Safety

 CautionThe main risk concerns knocking over the cans and spilling the hot water.

Care should be taken with mercury thermometers.

The contents of this page are for information only. Please refer to CLEAPSS or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.