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Warming Foods
Objectives
- To understand how certain materials become liquid when heat is applied.
Resources
Lined paper | Variety of materials for heating | Stop-watch or timer
Today's Lesson
Main Activity
Ask your child if they know what happens when a heated material, such as candle wax, is cooled again.
Collect a few different materials, for example, a candle, butter, sugar, Vaseline. Place the materials, one at a time, in a fire-proof container. [Note: a parent or other adult should be demonstrating this to your child.] Heat each material over a gentle flame until it has melted completely and turned to liquid. Use the correct words to describe the materials.
Then place the liquid in the fridge to cool, and then ask your child to observe the new state.
Some of the materials will revert completely to their original state; others, for example, butter, will become firm again, but will look different to the original state. The heated sugar will have changed colour and become one solid mass, rather than white crystals. However, all materials will have become solids again.
Water is a special material, because it has three readily observed states:
- it is a liquid at ‘room temperature’ (~20°C);
- when heated to 100°C, it becomes a gas;
- when cooled below 0°C, it freezes - it becomes a solid (ice).
Extension Activity
Collect any bits of candle that are too small to be burned anymore. Place them all in a heat proof container and melt them. You can buy a new wick and make a new candle!