What it shows
Heat travels along a solid by conduction. Metals pass heat quickly, while wood and plastic pass it slowly, so a bead stuck on a metal spoon with butter drops off first.
The science
In conduction, fast-moving particles at the hot end bump into neighbouring particles and pass energy along. In metals, free electrons carry energy quickly through the material, so metals are good conductors. Wood and plastic have few free electrons, so they are insulators and heat moves slowly. This is why pan handles are made of wood or plastic.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A steel spoon, a wooden spoon and a plastic spoon of the same size
- A tall glass or steel tumbler
- Hot water from a flask, about 70 degrees C (adult only)
- Butter or a little candle wax
- Three small beads or lentils
- A stopwatch
- A cloth and a tray
Safety
For this project: An adult must pour the hot water and stay with the children. Do not touch the hot water or the metal after it warms.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Stick a bead near the top of each spoon handle with a small blob of butter, at the same distance from the bowl of the spoon for all three.
Fill the glass with hot water poured by an adult and keep it on a tray.
Stand the three spoons in the glass with the bowls in the water and handles leaning out. Hold them in place with a clamp or tape if needed.
Start the timer and watch the beads. Note the time when each bead falls.
Stop at five minutes. Feel the top end of each handle carefully with a fingertip and note which feels warmest.
Record the time for each spoon in a table. If a bead has not fallen, write more than five minutes.
Repeat with a long strip of aluminium foil and a pencil as two more tests.
Rank all the materials from best to worst conductor.
What you should see
The bead on the steel spoon falls first, the beads on wood and plastic last or not at all. The steel handle feels warmest.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What is conduction?
The passing of heat through a solid from the hot end to the cooler end.
2Why do metals conduct better?
They have free electrons which carry heat energy quickly.
3Why are pan handles made of wood or plastic?
They are poor conductors, so the hand stays safe.
4Which would keep tea hot longer, a steel or a plastic cup?
A plastic cup, because it conducts heat away more slowly.
Take it further
Try copper wire, an iron nail and an aluminium spoon and place them in order from the best to the worst conductor.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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