Stirling Engine Runs from Heat Difference

1. Stirling Engine Runs from Heat Difference Materials: Low-temperature Stirling engine; mug of warm water/ice What you do: Place engine on warm source and spin flywheel gently. What students see: Engine continues running with no battery. Question: What is the 'fuel' if nothing is burning? 2. Ball-and-Ring Thermal Expansion Materials: Ball-and-ring apparatus; warm water/heat source; cooling water What you do: Show ball fits cold; warm ball or ring as apparatus permits. What students see: A tiny temperature change can stop/start the fit. Question: How can something get bigger without adding material? 3. Thermostat Bimetal Snap Materials: Bimetal thermostat/snap disc; warm water/hair dryer What you do: Warm element until it bends/snaps; cool it. What students see: Metal device moves suddenly by itself. Question: How can temperature become a mechanical switch?

Predict → observe three demonstrations → compare what changed → choose independent activity station → cleanup/share. Guiding questions: Question: What is the 'fuel' if nothing is burning? Question: How can something get bigger without adding material? Question: How can temperature become a mechanical switch?