It’s time for another edition of Mr. Russell’s classroom. On Wednesdays, Mr. Russell invites J-Stace the Science Ace to join him in class to show us a super cool experiment. Today, J-Stace explains the combustion reaction, but you’ll have to put some money down before you can fully understand the power of flammable liquids like alcohol.
What You Need
- 1/2 cup rubbing alcohol
- 1/2 cup water
- 2 tablespoons salt
- Metal tongs
- Dollar bill
- Kitchen Sink
- Measure out the rubbing alcohol and the water and pour it into the glass.
- Measure out the salt and add it to the liquid. Stir the solution together with your spoon.
- Using your tongs, pick up the dollar bill and dunk it completely in the solution. Gently swirl the bill
around and allow 20 seconds for the bill to absorb the solution.
- Using your tongs, remove the bill from the solution and still using your tongs, hold the wet bill over your
- Have your adult hold the lighter flame at the bottom corner of the wet bill and watch what happens.
Science Behind the Experiment
One of them was rubbing alcohol, which is a flammable liquid. So when you added fire to your dollar bill you were actually catching the rubbing alcohol on fire, not the paper money. When the fire ran out of rubbing alcohol to burn up it died out; it had run out of its fuel. Fire is actually a chemical reaction and chemical reactions only last as long as the chemicals last.
You also added water. Water is not a flammable liquid; we generally use it to put out fires. Water can stop the fire’s chemical reaction by taking away the heat. So when the alcohol was all used up by the flames they could not continue the reaction because the dollar bill was wet and not dry.
When the bill is soaked into the solution, the water molecules soak into the bill while the alcohol remains on the surface. When the match is put to the bill, the alcohol is what actually burns. The temperature at which the alcohol burns is not high enough to evaporate the water and burn the bill. So after the alcohol has burned, the dollar bill is still slightly wet. and the fire goes out.
Science Word of the Day: Flammable liquid – it has the ability to catch on fire.
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