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