Dry ice + fire = two of my kids all time favorite things to experiment with! (They have a thing for anything with the potential to explode or fizz.) So, of course a project with candles and dry ice was going to be instantly popular.
The cool thing about this experiment is that it is SO easy to set up (except for the buying dry ice part). But once you have the dry ice, you just need to grab a candle and cup. And if you're anything like us, those are always available!
* dry ice
Easy How To:
You may be familiar with the classic candle experiment where you cover a lit candle and watch the flame go out. Fire needs oxygen to burn. If you take away that oxygen, the fire will go out. This experiment is a fun variation on that cover-the-candle experiment.
1- Set the candle inside the cup and light it. Review fire's need for oxygen.
2- Place a piece of dry ice inside the cup near the candle.
SAFETY NOTE: Never touch dry ice directly. We used a large measuring spoon. Never drink dry ice.
Wait and watch the flame go out!
Dry ice is carbon dioxide. Carbon dioxide is heavier than our air, so as it sublimates (changes from a solid to a gas) it sits on the bottom of the cup. The normal oxygen-containing air is pushed up and out of the cup. As all the oxygen around the flame is removed, the flame goes out.
Make it an experiment:
The process I described above is a demonstration (which is wonderful, but) not an experiment. If your children are old and mature enough to experiment with dry ice and fire, let them test different variables and create their own experiment based on the knowledge covered above. I love to do a demonstration first, and then let the kids experiment with the concepts as they like. Here are a few experiment ideas:
1- Does the size and/or quantity of dry ice pieces affect how quickly the flame goes out?
2- Is the full cup filled with carbon dioxide or just a portion of it?
3- Is there carbon dioxide in areas that are not steamy?
4- Can the carbon dioxide over-fill the cup? How would you know?
5- Do different candles go out at different rates?
What else would you like to test?
I may share at any of these parties!
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