Inflate a balloon using the reaction between bicarb of soda and vinegar.
Empty small plastic bottle (fruit shoot type is ideal). Bicarb of soda 1 tbsp. Distilled vinegar 1/3 cup. One balloon. Funnel.
Carefully add 1 tbsp bicarb to the balloon using the funnel. Pour the vinegar into the bottle. Being very careful not to tip the powder out, fit the balloon onto the neck of the bottle and let it hang over the side. When you are ready to demo the reaction, lift the balloon up and shake it so that the bicarb falls into the vinegar. Make sure that the seal between the bottle and the balloon is not broken. Watch as the balloon inflates.