Convection and Conduction Experiments

The Science of Temperature and the Transfer of Heat Energy

Nov 1, 2009

Do experiments to test the way heat energy is transferred. Students will understand the difference between convection and conduction.

When the energy of the sun hits an object, some of the sun’s energy is transferred to the object’s molecules, heating them. When a person touches that warmed object then some of the energy in the object’s molecules is transferred to the molecules in the person’s skin. This transfer of heat is called conduction. If the heated molecules move to another location, this is called convection.

Student Activity for the Transfer of Energy

Have the students pretend to be the molecules in an object. They should stand in a circle and hold hands. Touch the shoulder of one of the students to indicate that the sun is warming this molecule. That person clenches his right hand around the left hand of the person whose hand he’s holding. That triggers this individual to then squeeze her right hand, pressing on the left hand of the person whose hand she’s holding.

This transfer continues around the circle until the left hand of the person who started the activity is squeezed. The hand squeezes should be brief and individuals should avoid treating this like an arm wrestling match. Time how long it takes for the energy of that first hand compression to work around the entire group. Discuss the definition of conduction.

Heat Conduction and Temperature Experiment

Give each team of students a cup of hot water and a cup of cold water. Have the students set a metal teaspoon in each cup. Note that the teaspoons feel the same temperature. Have the students check the apparent temperature of the spoons with their fingers every thirty seconds. The molecules of the spoon vibrate, causing even the handle of the spoon that isn’t in the water to change temperature.

Explanation of Convection

In convection, heated molecules aren’t transferring their heat to other molecules they are actually taking the heat with them to another place. When a fluid, a gas (like air) or a liquid (like the ocean), is warmed, its molecules move faster and move apart. The fluid then takes up more space although the number of molecules remains the same.

This means that the warmed fluid is less dense and weighs less than its cooler, denser surroundings. The warmer fluid will rise through its surroundings until it encounters something less dense than itself and it cools, becomes denser and heavier, and sinks.

Convection Experiment

This experiment from How the Weather Works by Michael Allaby [Dorling Kindersley, 1995] requires a cup that can hold hot water and fit into a clear jar that is at least twice as tall as the cup.

As the extremes between the water temperatures balance, the color will disperse throughout the entire jar.

These experiments and the activity show students the difference between conduction, the transfer of heat energy to adjacent molecules, and convection, the movement of heated molecules to other locations.

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