Endothermic chemical reaction use up heat energy, which means the end result is cool to the touch. Use Alka-Seltzer to see this reaction for yourself!
Things you’ll need: A beaker, a thermometer, an Alka-Seltzer tablet, ice, and water.
- Fill the beaker with ice. Add enough water to cover the ice fully.
- Put the thermometer in the beaker and read the temperature of the ice water after about one minute when the temperature is steady. Mine is 11°C (51°F).
- Add the Alka-Seltzer tablet to the beaker and read the thermometer. Mine is 6°C (42°F)
Melting ice absorbs heat and cools water until the ice water reaches the freezing point (0°C=32°F). Mixing Alka-Seltzer with the cold water was an endothermic reaction, meaning it used heat. An Alka-Seltzer tablet contains two main ingredients: sodium bicarbonate and citric acid. In the ice water, they reacted to form sodium citrate and carbon dioxide, which removed energy and further dropped the solution temperature. The Alka-Seltzer solution became super-cooled by the endothermic reaction.