| For years I taught about density as well as | | | | this just light another candle and slowly |
| the properties of carbon dioxide, though | | | | lower it into the aquarium. It will |
| never at the same time. Why it took so long | | | | extinguish itself once it gets below the |
| to put the two together, I'll never know. | | | | aquarium's opening. In fact, the carbon |
| Here then, are a few demonstrations involving | | | | dioxide will rest in the aquarium for quite |
| the density of carbon dioxide gas and a | | | | some time, especially if the room is |
| flame. These should be done by adults or | | | | still.Another demonstration to try is to make |
| under careful adult supervision as there is a | | | | a long trough out of V-shaped aluminum foil |
| potential of fire hazard.I suggest starting | | | | and use it as a guide for pouring carbon |
| by showing that air and carbon dioxide have | | | | dioxide. Place a candle in a candlestick |
| different characteristics. Hold a lit candle | | | | holder and light it. Place some baking soda |
| in a glass for a few moments. It keeps | | | | and vinegar in a large bottle and let the |
| burning. Now place a small amount of baking | | | | bottle fill with carbon dioxide. Now, hold |
| soda in the glass and pour in a bit of | | | | the aluminum foil trough so that one end is |
| vinegar. What do the kids see happening | | | | just above the candle flame. The other end |
| (bubbles) and what do they think is happening | | | | is held higher. If water was added to the |
| (gas is produced)? Now lower the lit candle | | | | trough, it would pour down and extinguish the |
| into the glass and it will go out instantly | | | | candle. We are going to do this with the |
| (the gas does not support the burning of the | | | | carbon dioxide instead. "Pour" the carbon |
| candle).For the next part of the | | | | dioxide from the bottle into the higher end |
| demonstration you will need several candles | | | | of the trough. The candle flame will flicker |
| of different height. You will want as many | | | | and usually extinguish at the lower end of |
| different heights as possible so some candles | | | | the trough. Why? (The carbon dioxide, being |
| may be broken, some placed on supports such | | | | more dense than air, actually does pour down |
| as candlestick holders, inverted coffee cups, | | | | the trough. Once it reaches the other end, |
| etc. I always hold these candles in place by | | | | it pours out of the trough and over the |
| lighting one and allowing the hot wax to drip | | | | candle flame. Since the gas does not support |
| onto the surface where I want a candle to be | | | | combustion, the flame flickers and goes out.) |
| placed. I then place the bottom end of the | | | | This should re-instill the idea that carbon |
| candle in the wax and allow the wax to | | | | dioxide is more dense than air, as well as |
| harden. The candle will be "glued" in place | | | | the fact that carbon dioxide does not support |
| by the cooling wax. I have the candles / | | | | combustion.A final thought... if you have |
| supports placed in the upright aquarium so | | | | easy access to affordable dry ice, it can be |
| that one corner remains open.Now, light all | | | | used in place of the baking soda and vinegar. |
| of the candles. The effect should be quite | | | | It really is just carbon dioxide gas cooled |
| pretty, but that is not the purpose. Place | | | | and compressed into solid form. If you |
| one cup of baking soda in the free corner of | | | | handle it, be sure to use gloves and tongs as |
| the aquarium. To this add two cups of | | | | it can quickly and easily cause |
| vinegar. The familiar bubbling will occur. | | | | frostbite.Until next time... keep having fun |
| By watching the candles, something intriguing | | | | with science!Thomas Smith owns and operates |
| will be seen. They will go out, one by one, | | | | Wonder Workshops, an online supply mecca of |
| from the candle closest to the aquarium | | | | retro toys, puzzles, puppets, magic tricks, |
| bottom to the uppermost candle. The reason? | | | | books, novelties, and DVDs, all based in |
| The carbon dioxide is more dense than air, | | | | science, math, and problem solving. Tom also |
| therefore it rests below the air in the | | | | presents hands-on, mind-on science workshops |
| aquarium. Since it is continually produced, | | | | for teachers and parents around the country. |
| it pushes the air out of the aquarium so that | | | | To find out more about the workshops and |
| it can remain below it. If enough vinegar / | | | | store, be sure to visit You'll be glad you |
| baking soda are added, the aquarium will | | | | did! |
| become brim full of carbon dioxide. To prove | | | | |