Thermal Conductivity

Purpose

In this experiment, students will investigate thermal conductivity (the ability of a material to transmit heat) by comparing heat transmission in an aluminium beverage can and a steel food can. This experiment also has a number of uncontrolled variables, which can be used to stimulate discussion about fair testing and controls in scientific experiments.

Activity

Students discuss whether good thermal conductivity is a requirement in the packaging of foods and beverages.

How long does it take to boil a given amount of water, eg 100ml, in an aluminium beverage can and in a steel food can? Vary the amount of water and graph the results for aluminium and steel.

Record the class results in a table and discuss.

Discussion

This discussion of experimental design could be done at a variety of levels.

Primary students should be introduced to the concept of fair testing eg what happens if we try to boil different amounts of water in the same size containers? Try it and discuss the results.

Secondary students could identify the uncontrolled variables eg thickness and surface area of the bottom of the can, mass of the can, size of flame. Discuss how these variables may be controlled in an ideal experiment. If practical, attempt to set up such an experiment and see if it makes a difference to the results obtained.

Extension

An additional or follow-up activity could be to investigate the thermal conductivity of aluminium beverage cans and PET plastic drink bottles. Place water of a known temperature into aluminium beverage cans and PET drink bottles and measure the water temperature after a given amount of time in a fridge/freezer. Students will need to do some preliminary investigations to test for the effect of water volume and time in the fridge/freezer to get a measurable effect.

For secondary students

Investigate the thermal conductivity of other materials. Use this experiment to distinguish between conductors and insulators. Discuss the use of insulation materials in everyday situations eg clothing, building insulation, polystyrene and paper cups for hot drinks.

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