Cold Chemistry

Cold Chemistry

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.

  1. Fill the beaker with ice. Add enough water to cover the ice fully.
  2. 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).
  3. 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.

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