The mysterious blast

Magic Science Tricks video.

TRICK Nº3. The mysterious blast


NOTE: This trick must heave adult supervision.

What we need:

• candles,
• matches,
• sodium bicarbonate, baking soda,
• vinegar, normal, without flavor,
• a glass container, with a large opening.

How to:

1. Light the candles;
2. Leave it burning for a while;
3. Pour the vinegar in container;
4. Add half a measure of bicarbonate;
5. Quickly put your hand over the cup, keep your hand there for a few seconds, until the bubbling calms down
6. Hold the container 1 in above the candle wick;
7. Tilt it as much as you can without the liquid content spill over the candles.

What happens?
The flame extinguish.

Why?
When we mix vinegar and baking soda a reaction happens, in this reaction water (liquid), carbon dioxide (gas) and sodium acetate (liquid) are formed. The bubbling is the result of this.
When we place our hand on the flask we don't prevent the gas to escape, we just slow it down, a small amount of it stay inside the container. When we tilt the container near the candles the CO2 escapes, and as result the O2 (oxygen) concentration drops, resulting in the extinction of the flame. This happens because one of the 3 necessary elements for a combustion is missing- the O2 -Check more information about this.

NOTE: CO2 molecule is heavier then O2 molecule.

That's why CO2 is a extinguishing agent, but like all extinguishing agents it can't be used indiscriminately:

Referências:
http://www.fiocruz.br/biosseguranca/Bis/lab_virtual/fogo.html 
http://www.fire-extinguisher101.com/agents.html

Et voilá!
It's Magic

Enjoy!