Discrepant Event

Julie Franzak

ELED 305-42

5/29/2007

Science Area: Chemistry

Concept: Dispersed Particles

The Magic Candle

Paradox #2

Materials:

Medium size candle

Book of matches

Draft-free room

Safety Considerations:

Be careful: flame, candle and matches will be hot.

Discrepancy:

Most students will not believe that the flame from the match will travel on the smoke from the candle that was blown out.

Procedures:

1. Light candle

-Allow time for the flame to grow in size

2. Strike a match

-Hold the just stricken match in one hand

3. Blow out the candle flame with a short puff

4. Immediately hole the burning match in the smoke trail of the candle

-About 3-4cm from the candle’s wick

5. Observe the flame travel from the lit match along the smoke trail from the candle

*smoke trail must be thick for this to work

Questions:

1. What causes the flame to travel from the match to the candlestick?

2. Why does this activity need to be administered in a room without a draft?

3. What is the candle actually burning?

4. If you took out the wick of the candle, would the lighted wax cause a flame?

5. Besides a wick, can anything else cause the wax to flame?

6. After the candle is blown out, what creates the smoke?

Explanation:

The vapor from the heated candle wax is what is actually burning the candle. When the candle is first lit, the wick immediately begins burning; the flame on the wick causes the wax to melt and systematically, the wick absorbs the molten wax and the vapors from the hot wax burn around the wick. Although the flame is extinguished when it is blown out, the hot wick continues to burn the molten wax causing the smoke trail. The smoke trail is composed of dispersed particles of wax in the air that are very small, yet still combustible. This is the reason why holding a lit match in the smoke trail causes the flame to travel to the wick of the candle.

“Magic Candles” are treated with red phosphorus; this treatment causes the candles to not blow out, or relight themselves. The glowing wick of the just extinguished “magic candle” causes the tiny red phosphorus particles to relight and the candle to flame again.

Source:

Liem, Tik L. Invitations to Science Inquiry: Supplemental 1^st and 2^nd Edition. Chino Hills, CA: Science Inquiry Enterprises, 1991. 67.