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	Link with activities in the manual
Exploring thermal expansion	30 minutes
A temperature sensor	30 minutes
Making a thermometer	45 minutes	Thermal Expansion #1, #2
Science content: thermal expansion	30 minutes
Discussion of thermal expansion	30 minutes

Another page relevant to this section: Why study thermal expansion?

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 ).