Building volcanoes with bicarbonate of soda is a rite of passage for both parents and children. It creates one of those iconic childhood memories, right up there with trick-or-treating, the first tooth under the pillow, and searching for Easter eggs. But there's no reason to limit yourself or your children to just that one experiment---you can try other fun projects as well.
Project kits are available in stores, but it's fairly easy to make your own volcano. First build your volcano out of papier-mache. Using a plastic bowl as a mould, layer bits of newspaper moistened with a mixture of flour and water until you've created a volcano as large as you want. Leave a depression at the top of the volcano about two inches deep and two to three inches wide. Now pour two to three teaspoons. of baking soda into the vent. When you're ready, add one-fourth cup or so of vinegar and stand back. For a more dramatic eruption, add food colouring to the vinegar.
Fire requires oxygen in order to burn. If that oxygen is replaced by carbon dioxide, the fire should be extinguished. When baking soda (a base) is mixed with vinegar (an acid), carbon dioxide is in fact produced, and the birthday candle in this experiment does go out. Place the candle upright in a short, narrow glass or small jar by sticking it in a small mound of clay on the bottom. If you don't have clay, use drops of melted candle wax as your candle base. Sprinkle two teaspoons of baking soda on the bottom and light the candle. Now gently pour in some vinegar (away from the flame) to get the soda fizzing. The candle should go out in a minute or so.
This experiment again demonstrates that mixing an acid (vinegar) and a base (baking soda) produces a gas (carbon dioxide). To make a bubble bomb, test a zipper-lock sandwich bag for holes by adding some water and shaking it around. Use one that is leakproof. To begin the experiment, cut a paper towel into a five-inch square and put one and one-half tablespoons of baking soda in the centre of the square. Fold it three or four times to form a small packet. Next, pour one-half cup vinegar and one-fourth cup warm water into the plastic bag. Quickly drop the soda packet into the bag and zip the bag closed before too much fizzing starts. Shake the bag a little. Stand back and wait for the bag to puff up and then pop with a bang, shooting water in all directions.