A received this great kit from his aunties. It's the perfect starting out kit for younger ones since everything fizzes and foams.
The first experiment was a version of the fizzing volcano. If I remember correctly we mixed water and citric acid, then added baking soda to finish the reaction.
There were enough materials for each of the boys to participate and they took turns measuring out all of their ingredients. The kit comes with everything we needed except for basics like bowls and something to catch the explosion in.
Love this picture of A seeing his experiment working! He closely examined the results to see if he could find air bubbles.