EDSE 452/453 Inquiry Demonstration

The Magic Candle

 

Created By: Christy Cachero

Grade: Science 7

Science Concept: Unit C – Heat and Temperature (introduction to the particle model of matter)

 

Question(s) and Answer(s):

  1. How does a candle burn?  OR What is actually burning of the candle?

- It is the molten wax that allows a candle to burn.  The wick burns first when a candle is initially lit and the flame melts the surrounding candle wax.  The wick absorbs the molten wax and the hot wax vapors burn around the wick, allowing the candle to continue to burn.

 

  1. What creates the smoke after a candle is blown out?

- The hot wick keeps heating the molten wax, forming a trail of smoke after a candle is blown out.

 

3.       What makes the flame travel to the wick?

- The smoke consists of very small dispersed partially burned particles of wax in the air.  Since it is the wax that allows a candle to burn, a flame held within the smoke trail lights these particles, causing the flame to “travel” to the wick.

 

4.       Why does this demonstration have to be performed in a draft-free room?

- So that the flame may ignite the smoke trail, traveling to the wick and lighting the candle.

 

Required Materials:

1.       A book of matches

2.       A medium-sized candle

 

Demonstration Description:  Note – A draft-free room is required for this demonstration.

 

  1. Light the candle and allow it to burn so the wax begins to melt and the flame is a good size.
  2. Light another match.  Blow out the candle flame while still holding the burning match.
  3. Immediately hold the burning match in the smoke trail about 2 – 3 cm from the wick.

 

 

Explanation:

            It is not actually the wick alone that allows a candle to burn.  When ignited, the wick burns down until the flame begins to melt the wax.  The molten wax is absorbed by the wick and the wax vapors are burned around the wick, allowing the candle to continue to burn.  When a candle flame is extinguished, a smoke trail rises from the wick.  This is because the hot wick continues to heat the wax.  The smoke is made up of tiny dispersed particles of partially burned wax.  When a match flame is held within these particles, the “smoke trail” is set on fire and the flame “travels” to the wick, relighting the candle.

 

Reference:

Liem, Tik L.. Invitations to Science Inquiry. 2nd ed. California: Science Inquiry Enterprises, 1987.