Junior Science. Heat. By the end of this lesson you should be able to. OP22: understand that heat is a form of energy and that it can be converted into other forms of energy OP23: investigate and describe the expansion of solids, liquids and gases when heated, and contraction when cooled
The cup is on a sharp point, e.g. a pencil or the holder of a compass needle.
About 100 B.C., a Greek inventor known as Hero of Alexandria came up with a new invention that depended on the mechanical interaction of heat and water.
He invented a rocket-like device called an aeolipile. It used steam for propulsion.
Hero mounted a sphere on top of a water kettle. A fire below the kettle turned the water into steam, and the gas travelled through the pipes to the sphere.
Two L-shaped tubes on opposite sides of the sphere allowed the gas to escape, and in doing so gave a thrust to the sphere that caused it to rotate.
This showed that heat was a form of energy.
The temperature of a tube of water was recorded every 30 seconds as it cooled from an initial temperature of 22°C
The small container for the water can be made using a plastic pipette dropper.
Cut off the dropping end, three-quarter fill with water and insert the temperature probe.
As the temperature drops, the energy of the particles in the substance reduces. The particles start to join together. As the particles join together, bonds are formed. When bonds are formed, heat is given out; this heat stops the temperature falling further so while the liquid is changing to solid, there is no further decrease in temperature. .
Supercooling - particles haven’t got organised to form crystals yet
Eventually, all the water turns to ice, no more particles join together, so now the temperature can continue to drop
Completely cool !