What you will need:
Baking soda
White vinegar
Measuring cups
One or more candles
Lighter or matches
Stable flat surface
Tall pitcher or large glass
* Adult supervision
The Set Up
First, prepare the baking soda and vinegar. Measure out about 1/4 cup of baking soda and around 1/2 cup of vinegar (if you’re container is smaller use smaller amount to avoid a mess). Once you’ve done that, set them aside and you can light the candle.
Next, mix the baking soda and vinegar. Pour the baking soda in first and then slowly add the vinegar. This will help keep it from bubbling over. Once the reaction has settled down you’re ready to put the candle out.
The Experiment
Take the container and make a pouring motion directly above the flame as if you were pouring liquid onto it.
Note: Do not pour the liquid onto the flame.
It might take a little practice with your aim but the flame should go out. You’ll know when you’re close as it will usually flicker before going out. If it doesn’t then you can mix more baking soda and vinegar and try again. If you had trouble getting the flame to go out, the next section might help.
What’s Happening?
The active ingredient in vinegar is acetic acid (5% usually). It’s this acid that reacts with the baking soda (sodium bicarbonate). The reaction, as you can see, can be pretty vigorous. The byproducts of the reaction are sodium acetate, water and carbon dioxide. Carbon dioxide (CO2) is the one we’re interested in because it is what puts the fire out.
Carbon dioxide is heavier than the surrounding air and this allows us to trap it in a tall container and pour it onto the flame as if pouring a liquid. The carbon dioxide gas deprives the candle of oxygen and extinguishes the flame.
Extra Credit
Try putting out multiple candles at once. Can you think of another way to cut off the oxygen supply to the candle using the materials on hand? Remember to ask your parents for help!
All the world is a laboratory to the inquiring mind. – Martin H. Fischer
* Remember, safety first! Children should have adult supervision when doing this.
He’s a nifty video showing it in action