The kids started off with calcium chloride, sodium bicarbonate (see if your kids remember this compound's common name...it's baking soda), water, and phenol red, an indicator for acids. They put all of these materials in a plastic bag, the catch being that the liquids (water and phenol red) were first poured into plastic cups, which themselves were carefully placed in the bag.
After closing the bag, the kids allowed the powders and liquids to mix, and that's when things got exciting! The kids observed many changes including: bubbles, the bag inflating, the red liquid turning yellow, and the contents both heating up and cooling down. The real challenge came next when the kids had to figure out which combinations of ingredients caused which results.