Time to celebrate science! Use this birthday candle experiment to explore combustion
“Burning candles lose mass”. Use this knowledge to make a timer.
This experiment should take 60 minutes.
- Eye protection
- Clamp stand
- Heat-resistant mats
- Card or stiff paper
- Wooden splint
- Plasticine or blu-tack to balance the splint
- A timer
- Rule, 30 cm
- A pencil
- 2 or 3 birthday cake candles (the candles with the spiral markings seem to work better than the plain candles).
Health, safety and technical notes
- Read our standard health and safety guidance here.
- Wear eye protection.
- Hot wax can burn, and stain clothes. Wear protective gloves and/or clothing if desired.
- This is an open-ended problem-solving activity, so the guidance given here is necessarily incomplete.
- If the candle is allowed to burn down too far, it sets light to the splint.
- If the scale is too close to the flame, it too may burn.
- Take care if any nearby activities involve flammable or combustible substances.
Students make a timer by fixing a birthday cake candle on one end of a splint, pivoted with a pin, in a cork held in a clamp stand. They will need to find a way of making a scale against which the other end of the splint moves.
This scale is then calibrated using a timer. The core of the problem is to get the splint to pivot easily - but not too easily. It is possible to get repeatable results, given care.
E.g. A birthday cake candle timer -
*the friction between the pin and the wooden splint is important. It can be altered by changing the amount of pressure of the pin against the cork.
- PDF, Size 72.91 kb
The resources were originally published in the book In Search of Solution P. Borrows, K. Davies and R. Lewin, Royal Society of Chemistry, 1990.
This experiment was based on an idea contributed by S. Lindley.