Things change size with temperature. It isn't a big effect, but it is very reliable -- inexorable might be the better word -- and for this reason it is the principle on which many common thermometers are based.

Main Pages	Estimated time required
Exploring thermal expansion	30 minutes
A temperature sensor	30 minutes
Making a thermometer	45 minutes
Science content: thermal expansion	30 minutes
Discussion of thermal expansion	30 minutes

Materials needed for this section

• Clear plastic tape, aluminum foil, and a dark marking pen (any color).
• A sunny day* (for direct sunlight) or a bright incandescent lamp.
• Thermometers*
• Flower tubes* and plastic straws*
• Hot water and ice water (please see the section local materials ).

Next section:Thermal sensing sheets