Combining baking soda (a base) and vinegar (an acid) causes a chemical reaction and creates carbon dioxide gas. Add mothballs to the equation and watch what happens when a solid with rough edges gets hit by the gas bubbles. Create a thorough science project by trying each experiment several times, changing one variable each time.
Half-fill a glass with water and add 1/4 cup of vinegar. Add a teaspoon of baking soda and stir. Drop in some mothballs and watch them move up and down. The carbon dioxide bubbles created by the chemical reaction catch on the rough sides of the mothballs and cause them to bob. Try the experiment with baking powder and see if there is a difference. Try dropping mothballs into a glass of pop and see if there is any difference between the liquids where you created carbon dioxide and the liquid that already had carbon dioxide in it.
Do this experiment over a sink, bathtub or wash tub. Measure 1/2 cup of vinegar and 1/4 cup of warm water into a plastic bag with a zipper. Zip the bag and turn it upside down to make sure there are no leaks. Measure 1 1/2 tbsps. of baking soda into the center of a small paper towel. Fold the paper towel a few times to make a small packet. Open the plastic bag, drop the paper towel in, and very quickly zip the bag. Place the bag into the washtub and back away. The bag should pop open and fizzy water should spray out. Try the experiment again, this time adding mothballs to the bag before adding the baking soda paper towel. The mothballs may remain in the bag or they may fly all over the room when the bag pops, depending on the speed with which the bag is zipped closed after adding the baking soda packet. If the packet is released into the bag and the bag is zipped immediately, mothballs will pop out of the bag when it bursts.Try the experiment several times and record your results.
Pour 1/4 cup of vinegar and 1/4 cup of water into an empty pop bottle. Use a funnel to fill a balloon half full of baking soda. Fold the part of the balloon filled with soda to the side. Stretch the balloon over the mouth of the pop bottle. Lift the balloon to pour in the baking soda once the base of the balloon is sealed over the pop bottle opening. Watch the balloon inflate. Try the experiment again, but this time put some mothballs in the pop bottle before putting the balloon on top. If they are too large to fit into the bottle, cut them in half. The mothballs will rise to the top of the bottle, and they may enter the balloon once the baking soda is released into the liquid solution. Results will vary; do the experiment several times and write down what happens to the mothballs each time.
Volcano with Boulders
Put some baking soda in a short cup. Pour on vinegar and watch the mixture bubble up and out of the container. For a dramatic look, build a papier mache volcano sculpture around your container. Put some mothballs in the container with the baking soda, then pour in the vinegar and watch the mothball "boulders" come down the sides of the volcano with the bubbly "lava."
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