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Wednesday, January 11, 2012

Light a Candle without touching the wick

This week we will explain the magic tricks in the video "Top 10 quirky science tricks for parties" we saw here.

TRICK Nº1: Light a Candle without touching the wick
NOTE: This trick must heave adult supervision.

What we need:
  • a candle,
  • matches, or a lighter
How to:
  1. Light the candle;
  2. Let it burn for a few seconds, until the wick turns incandescent;
  3. Blow out the candle, you will see a thin smoke "string" going up;
  4. Light another match, quickly, this time place it 1 or 2 in above the wick.
What happened?
The candle reignited.

The explanation is very simple, but often overlooked.
First of all fire needs 3 things to burn,
  1. Oxygen;
  2. Fuel;
  3. and a Ignition;
In this magic trick, oxygen is all over, the paraffin is the fuel and the lighters the ignition.
The wick burns and at the same time the wax burns, is consumed, in this process energy is released.

If you look close enough to the candle while it burns, you can see smoke, that smoke is the result of paraffin wax combustion when you bow out the candle the smoke gets bigger, this means the fuel wasn't all consumed, some of it is released in the air as vaporized paraffin. When we provide a new source of ignition- the second match- the fuel in that smoke reignite the flame that travels down to the wick, and reignite it

Transform this demonstration in a experiment
Aldo the most of the candles are made of paraffin, you can try different types of candles:

  • Try to understand what kind of candle works best.
  • Maybe the scented candles don't reignite?
  • What happen with a gel candle?
  • Beeswax candle ignite faster or slowe?
  • What kind of candles burn with less smoke? 
Note: The smoke produced during a fire tells us about combustion efficiency. A flame with a great amount of smoke means a low efficiency combustion- many of the fuel is not burned-, on the other hand a flame with "no smoke" means a great efficiency combustion- almost all the fuel is consumed during the fire.

Et voilá!
Never play with fire without adult supervision!


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