Have you ever sat around a campfire and watched it dance and glow? Have you ever wondered about the science of fire? We know it is hot. We know it needs something to burn, like paper or wood. We know it is usually orange or yellow, depending on the materials that are being burned. And we know that it needs oxygen to “stay alive”.
There are several different ways to deprive a fire of oxygen so that it will go out. You can dump water on it. You can put something like dirt or sand on top of it. For small fires, like candles and matches, you can simply just blow on it.
So why does a candle go out when you blow on it? One of the possible explanations is that when you exhale you breathe out a lot of carbon dioxide. That carbon dioxide displaces the oxygen around the fire, making it go out. Some fire extinguishers even use carbon dioxide (among other chemicals) to put out larger fires.
In this experiment we made our own fire extinguisher using vinegar and baking soda. The reaction of these two materials produces carbon dioxide, which you can see bubbling up through the solution. Carbon dioxide is heavier than air so it drops right on top of our candle to put the flame out.
- Have an adult light the candle.
- Add vinegar to your bottle.
- Using a funnel, quickly drop the baking soda into the bottle.
- Being careful not to spill your mixture, hold the bottle at an angle so the carbon dioxide can flow out onto the fire.
- Notice how carbon dioxide is heavier than air and drops right onto the flame to extinguish it!
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