Go to Top Background Dissolving calcium chloride is exothermic. If the water solution first contacts the calcium chloride, it heats. Reactions from the warm solution proceed quickly. Dissolving sodium bicarbonate is endothermic. If the water solution first contacts the sodium bicarbonate, it cools slightly.
Cooled reactions proceed slowly.
The sealed bag fills with gas. The carbon dioxide is acidic and changes the color of the phenol red from red to yellow. Students can vary the relative amounts of the chemicals, and select different chemicals on which to place the added liquid inside the sealed sack. Go to Top Makeup Ans. Two reactants are mixed inside a plastic bag.