Calcium chloride is added to water in a plastic bag. As the chemical splits apart, it releases a noticeable amount of heat. An acid-base indicator, phenol red, is then added to the baggie along with sodium bicarbonate (regular, old baking soda) and zipped closed. As the two chemicals react with one another, a large amount of carbon dioxide gas is released, the indicator changes color from red to yellow, and, if you are lucky, the bag will explode. It is the perfect post-mexican dinner reaction: you get very hot, generate a lot of gas and something has to give.
Demo Pack includes 7/8 oz. Calcium Chloride, 7/8 oz. Sodium Bicarbonate, 2 - 1 oz. Phenol Red, 2 Baggies
Classroom Pack includes 10 7/8-oz. Calcium Chloride, 10 7/8-oz. Sodium Bicarbonate, 20 1-oz. Phenol red, 20 Baggies
Classroom Refill Pack includes 16 oz. Calcium Chloride, 16 oz. sodium bicarbonate, 32 oz. Phenol Red, 20 Baggies