A ziplock bag is inflated by mixing three substances in it
name: Exothermic reaction between calcium chloride and sodium bicarbonate. Color of the indicator changes due to the formation of carbonic acid.
Interaction of calcium chloride with sodium bicarbonate leads to the formation of carbon dioxide that fills the bag.
This reaction is exothermic, and therefore, it forms calcium carbonate and carbon dioxide, instead of calcium hydrogen carbonate. The color change of the indicator is caused by changes in the reaction medium due to the formation of carbonic acid.