Science Fair

In this special article, we introduce two science fair experiments involving candles. One is based on the chemistry and physics of burning candles, and the other tests human behavior with trick candles.

BE CAREFUL! This project involves fire, which is ALWAYS DANGEROUS. Be sure you have adult supervision before proceeding.


Project #1:
Trick Candles and Human Behavior

We’ve all been there: you blow out the candles on your cake, but one candle just won’t go out! Sometimes candles will be ornery like this on their own, but most of the time it means you’ve been pranked. This science fair experiment tests how long people will continue trying to blow out a candle before they realize it’s a trick candle.


  • 30 regular birthday candles
  • 6 “trick” self-lighting candles
  • something to hold the candles in – a small candelabra or even a cupcake!
  • At least 25 participants


1. Come up with your hypothesis – how many times do you think people will blow on a trick candle before they realize it’s a joke?

2. Arrange your candles on a holder or cupcake. It’s best to have about 5 regular candles with 1 trick candle, but the exact number will depend on what you are using to hold the candles up.

3. Present the candles to your subject and ask him or her to blow them out.

4. Silently count the number of separate puffs your subject makes. When they give up or finally succeed in blowing out the trick candle, write down the number.

5. Repeat for all participants, then take the average. Was your hypothesis confirmed?

*TIP: You can make these science fair experiments much more scientific by testing a variable such as age or gender along with number of times it takes to blow the candle out. Do older people give up more easily? Are women more likely to keep trying than men? You can find out with your science fair experiments


Project #2:
Candle time and room temperature


  • 15 medium-size wax candles
  • Air conditioning
  • Space heater
  • Nail or fork
  • thermometer


1. Come up with your hypothesis – do you think that candles will burn fastest in warm or cold environments?

2. Measure your candles. They should all be brand-new, so all of them should have the same length.

3. Run the air-conditioner in one room, space heater in another, and leave another room at a mild temperature. Leave a thermometer in each room and wait for the temperature to adjust (one hour or so)

4. Write down the temperature in each room.

5. Place 5 candles in each of the rooms and light them. Return every 15 minutes to measure all of the candles. Keep a separate data sheet for each room, and track the time, temperature, and length of all 5 candles in each.

6. When all 15 candles have burned out, plot your results on a graph with time on the x-axis (horizontal) and average length in each room on the y-axis. At the end, you should have a graph with three lines on it, all sloping down. Do they slope down at different rates? Are the results consistent with your hypothesis?

*TIP: These science projects for kids can also be done without air conditioning or a heater: simply place one candle in the refrigerator (preferably without anything else in it, since the smoke will make for an unpleasant taste), and one under a 40-watt bulb. Make sure to place thermometers next to the candles.


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