The Invisible Fire Extinguisher Learn how to blow out a candle with invisible carbon dioxide gas. email to friend
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1. You'll need an adult to help you make a few of the props you need for the experiment. If, on the other hand, you're the adult doing this experiment, find a cool kid to help you make this fun.
2. Start by removing the top of each of the plastic soda bottles. Either a one or two liter size bottle will work - just make sure you have two of the same size bottles. You're turning the soda bottles into inexpensive cylinders. Keep the two funnels for another project or drop them into a recycling bin.
3. You'll need to use your creativity to make the candle holder out of the coat hanger. The object is to lower the lighted candle into the soda bottle (your new cylinder) without burning yourself. See the photo for one possible solution. Again, you'll need an adult helper to light the candle.
4. Start by putting on your safety glasses. Light the candle and lower it into one of the empty soda bottle cylinders. This proves that the candle does not go out when you lower it into the container. Remove the candle and blow it out.
5. Pour approximately 3 ounces of vinegar into the cylinder and add one tablespoon of baking soda. The mixture will immediately begin to fizz and bubble. It's important that you do not pick up the cylinder - just leave it on the table (you'll see why later).
   
6. After all of the bubbling has stopped, light the candle and slowly lower it into the soda bottle cylinder. Why does the candle go out? Relight the candle and try it again. Carefully observe the place in the cylinder where the candle goes out. The cylinder is filled with an invisible gas called carbon dioxide and this gas extinguishes the flame.
   
7. Light the candle and lower it into the second soda bottle cylinder. Just as you observed at the start, the candle should not go out because there's a sufficient amount of oxygen in cylinder. Remove the candle and blow it out.
8. Here comes the fun part... Pick up the cylinder with the invisible carbon dioxide gas and slowly pour the gas into the second cylinder. This is tricky because you're pouring an invisible gas! Just make sure that you don't pour any of the liquid into the second container.
9. It's time for the proof. Light the candle and lower it into the container that used to have the carbon dioxide gas - the candle should stay lit - proving that all of the gas is now gone. Immediately lower the candle into the second container... and the candle goes out! Did you really transfer an invisible gas from one container to the other?
10. Listen to the sounds of ooohs and ahhhs and take your well deserved bow.

How does it work?

Let's start with the process of making the carbon dioxide gas. Baking soda is actually called sodium bicarbonate, NaHCO3. Vinegar is the household name for weak acetic acid, CH3CO2H, in water. Sodium bicarbonate reacts with an acid, such as vinegar, to produce carbon dioxide gas. As you observed first hand, carbon dioxide gas can extinguish a fire. It does this by reducing the amount of oxygen in the air around the burning object. Oxygen in the air is necessary for a fire, and when this oxygen is removed, the fire goes out.

It's also important to know that carbon dioxide has a density greater than air. As a result, it flows to the bottom of the cylinder filled with air by pushing the air up and out of the cylinder. Pouring a gas is like pouring a liquid. This property makes it easy to fill containers with carbon dioxide and to pour carbon dioxide from one container to another.

Some fire extinguishers are filled with compressed carbon dioxide gas while other fire extinguishers contain a special powder mixture used to extinguish a wide variety of fires.