This is a lovely activity to show the effect of convection. Little ones will love it just for the moving snake and it is a great way to get older ones to start thinking about the process.
You will need:
The snake picture
A heat source
1. First of all print out the attached picture of the snake or draw your own.
2. Colour and decorate as you wish
3. Cut out the snake so that it makes a spiral.
4. Thread the cotton and tie a knot at the end.
5. Thread it through the dot on the tail.
6. Hold it over a heat source…a lamp that has been on for a while works but over the stove is very effective or a candle.
Safety! Please remember to hold the snake out of reach of the flame and that it can be a potential fire hazard. Supervision of children is essential.
Why does this work?
Convection is the transfer of heat in a fluid. A fluid is usually a liquid or a gas!
In the case of the snake it is the air molecules that are being moved. As the molecules near the heat source warm, they move further apart. This makes the gas (or air) less dense and so it rises being replaced by cooler more dense molecules. The molecules as they rise lose heat, come back close together (increasing density) and sink again and the cycle continues. This circular movement of air particles rises and falling causes the snake to spin. We call it a convection current.
This process is how radiators work to heat our homes. The hot water inside the radiator heat the radiator by the process of conduction, however the now hot radiator heats the air around it which spreads into the room as it becomes less dense. This is replaced by cooler more dense air which is then heated!