CO₂ Candle Snuffer

The fire is dying.

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Purpose -

This demo shows the retarding effect of carbon dioxide on flames, and also shows the density of carbon dioxide compared with air.

Nature - 

Demonstration

Materials - 

Two candles of different heights, a large see through bowl or a small aquarium 10 - 15 L, 250ml beaker, vinegar, baking soda

Method - 

· Place the baking soda into the beaker, then put the beaker into the centre of the aquarium.

· Stand both the candles in the aquarium and light them

· Pour the vinegar into the beaker and note the reaction.

· After a while the short candle should go out, later followed be the taller one.

Safety -

Simple caution with matches

Explanation -

The reaction between vinegar (an acid) and baking soda (a carbonate) creates invisible carbon dioxide gas which is seen bubbling off.  this is denser than air so it fills the beaker, then spills over into aquarium filling it also.  A candle flame requires oxygen to burn, so as the level of carbon dioxide in the aquarium reaches each flame, it snuffs out.

Notes -

If you have difficulty getting enough gas to effectively snuff the candles, try using a Petri dish instead of the beaker.  

The reaction between Baking soda and vinegar is given here.

NaHCO3 + CH3COOH --> CO2 + H2O + NaCH3COO