Together with children, we make a lava lamp. The lava lamp itself is based on the reaction of baking soda and acid (such as citric acid or vinegar), where carbon dioxide is released from the composition of baking soda (NaHCO3) during the reaction. When the reaction is allowed to occur in a non-water-soluble environment, such as oil, carbon dioxide is released in bubbles, which creates the lava lamp effect.
Older children and adults learned about the reaction and why it occurs, while with younger children we talked about what carbon dioxide is. In addition, we talked about why water does not dissolve in oil and what density is.