MadSci Network: Edible/Inedible Experiments Archive

Nonflammable Gases

Area of Science: Chemistry
Meant for Grade 7-9 (age 11-13).
This experiment is inedible.
An adult should be present.

Mixing vinegar with baking soda in a glass container housing a lit candle will make the candle go out.

1. Candle - short birthday cake candles work well.
2. Glass container such as a glass or a clean, empty jar.
3. Vinegar
4. Baking soda (not powder).

Always be careful with flames.

How to do the experiment:
1. Light the candle. Drip some wax in the bottom of your glass container and stick the candle in it so it stands upright. The experiment works best if the tip of the candle is some distance from the rim of the glass, and if the container is fairly narrow.
2. Sprinkle baking soda into the jar, avaoiding the flame as much as possible. Alternatively if you have something in which you can stand the candle, place the baking soda in the jar before you place the candle in it.
3. Gently pour in some vinegar - enough to keep the powder fizzling and popping.
4. Observe the candle - after some time it should go out.

See the file - Baking Soda Volcano for the chemistry behind the above reaction. Note that the reaction produces carbon dioxide gas (CO2). Unlike oxygen gas (O2), CO2 is not readily combusted by the flame. It is also *heavier* than the other gasses which make up our atmosphere. Nitrogen gas (N2 - ~75% of the atmosphere) has an atomic weight of 30; O2 - a weight of 32 (~20% of air). CO2 has a weight of 44 (C = 12 a.m.u + (2 O = 2X16 a.m.u) = 44). It thus *sinks* to the bottom of your jar when evolved from the vinegar/baking soda mixture. If enough is created, it will reach the level of the flame. When the candle can no longer continue combusting its material with oxygen, it goes out.

Incidentally, for this reason, many fire extinguishers use compressed CO2 to put out fires. By filling the space around the fire with CO2, you essentially suffocate the fire. Unfortunately since we need oxygen gas to survive, breathing pure CO2 also suffocates us.

Experiment submitted on Tue Jan 28 04:02:12 1997 by:
Name: Nick Bourbaki
Institution: WashU Med School
Position: MadSci Admin

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