Science project

Burning Candles for Science!

This project demonstrates how scientists can identify different gases based on their properties.

Research Question:

What gas is formed when baking soda and vinegar mix?

If you give a candle plenty of oxygen, it will continue to burn. Other gases make candles burn more strongly or go out completely. When a chemical reaction forms a gas, you can figure out what type of gas it is by seeing what its reaction is.


  • Vinegar
  • Balloon
  • Funnel
  • Baking soda
  • Flask with narrow mouth
  • Birthday candle
  • Clay
  • Glass jar with wide mouth

Experimental Procedure:

  1. Measure 50 ml of vinegar and add it to the flask.
  2. Stretch the mouth of the balloon over the funnel so that it is securely attached.
  3. Pour a teaspoon of baking soda into the funnel, and shake or tap it so that all of the baking soda falls into the balloon.
  4. Remove the balloon from the funnel.
  5. Stretch the mouth of the balloon over the opening of the flask so that it is securely attached.
  6. Lift up the wide part of the balloon and shake it gently so that the baking soda falls into the vinegar. The chemical reaction between the vinegar and the baking soda will produce gas, which should fill up the balloon.
  7. Consider which gas might be in the balloon, based on the chemical formulae for baking soda and vinegar. (Answer: It could be oxygen, carbon dioxide, or hydrogen.)
  8. Based on your research, think about what would happen if each of those gases were held near a lit candle. (Answer: If it were oxygen or hydrogen, it would continue to burn or burn more quickly; if it were carbon dioxide, it would extinguish the flame.)
  9. Poke the candle into a large lump of clay, and place the clay onto the bottom of a large jar. Make sure that the candle it standing securely.
  10. Light the candle, and let it burn until it is just an inch or two tall.
  11. Grasp the neck of the balloon so that the gas stays inside, and remove it from the flask.
  12. Hold the balloon over the jar with the candle inside. Slowly release the gas, while the mouth of the balloon is pointed into the jar, but away from the candle.
  13. Observe the results. Which gas do you think was inside the balloon?

Terms/Concepts: Chemical reaction; What elements make up baking soda and vinegar?; What effect do oxygen, carbon dioxide, and hydrogen have on a burning flame?


  • Easy Genius Science Projects with Chemistry, by Robert Gardener. Pp. 50-52.
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