Thursday, December 26, 2013

Dry Ice #8: Dry Ice Fire Extinguisher

This is the eighth segment in a series on dry ice experiments. CLICK HERE FOR SAFETY INFORMATION.

I set up this experiment a bit more than the others. The previous week we did an experiment that showed that gas was a fluid and could be poured.

I placed a small chunk of dry ice in a glass (really a tub that used to have cocoa in it) of warm water where it began sublimating rapidly. I lit a candle (I used one that was in a jar), and then poured the mist—and heavy carbon dioxide gas—into the candle, being careful to not pour the water. The candle went out.

Why this works: carbon dioxide, a fluid, is heavier than air, so it displaces the room air (and oxygen) away from the candle. Fire needs oxygen to burn, so the without oxygen, the candle burns out.

The tricky part is pouring the gas and not the water. When I repeated the experiment for the kids, I ended up pouring water all over the candle. That put it out, too. 

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