Burning Questions

Students investigate combustion of a candle and measure mass changes as the candle burns.

Lab Summary

Students will investigate the combustion of a candle and measure how the candle’s mass changes as it burns.

Although evidence suggests candles were used as far back as ancient times, little is known of the exact origins of candles. The ancient Egyptians may have used rushes soaked in tallow (animal fat) as candles, but the Romans are credited with first developing the wick candle. Over the years candles have been made from a variety of substances, including tallow, beeswax, wax from bayberries and spermaceti (obtained from sperm whale oil). Today most candles are made from paraffin wax and stearic acid.

As a candle burns, it reacts with oxygen (O2) in the air to produce energy (heat and light), carbon dioxide (CO2) and water (H2O). Other products, including soot, may also form.

Consider generating a list of questions for students to investigate that will give them insight into the physical and chemical processes occurring as a candle burns. For example,

   *   How does the temperature of the flame vary from the top to the bottom?
   *   Is there liquid formed during the burning of the candle?
   *   Is the top of the candle level, concave or convex while burning?
   *   Does the wick or the wax burn, or both?

Hypothesize: Predict what will happen to the mass of a candle as it burns?

Published: April 2003

Downloads

• Burning Questions (27 KB, .zip)

  Includes experiment setup and procedures

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Other Materials

• Candle
• Aluminum foil
• Safety matches