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Candles

Students explore the melting and solidification of wax.

Students observe wax as it is heated and cooled, and make observations about this substance as it changes from a solid to a liquid, and back again.  

Objectives

  • Describe the properties of a solid and a liquid.
    Describe the processes of melting and solidification.

Materials

  • Wax
    Double boiler (you can use a coffee can in a saucepan of water)
    Hot plate, goggles, tongs as equipment for melting wax
    One (3–5oz) paper cup (“Dixie cup”) for each student
    One wick per student (available at craft stores, or try Wicks and Wax)
    Crayons
    Scissors

Key Questions

  • How does the wax look most of the time, before we add heat to it? What happens when we add heat? Does it look different after cooling? What changes of state did you see? Did the crayons stay in small pieces or did the colour spread throughout the hot wax? Why?

What To Do

  1. Melt the wax using the double boiler. Keep students away from the hot wax!
  2. Each student gets a cup, wick, and (optional) crayons. 
  3. Students label their cups and then set a wick inside. 
  4. Have them select a crayon colour, shave off pieces with scissors, and drop the shavings into the cup.
  5. Adults pour wax into the cup over the wick and crayon pieces. Set the candle aside for at least an hour.
  6. The following day, the cup can be peeled off the wax, so the candle can be used.

Teacher tips:

  • Make sure students know that the candles will not be ready to go home immediately.
  • Place candles out of the way until fully cooled.

Extensions

  • When a candle burns the wax must travel up the wick then evaporate whereupon it will react with oxygen. It is possible to see that the wax evaporates by letting a candle burn then blowing it out, after-which a stream of gaseous wax particles can be seen (students may interpret this as smoke). You can relight the candle buy placing a match in the stream or particles, you don't need to touch the wick!

Other Resources

Science World Resources | Full Unit | States of Matter
Science World at TELUS World of Science | School Programs | Chemistry
Make a Virtual Polymer