Endothermic Chemical Reaction

Most endothermic reactions contain toxic chemicals, but this reaction is safe and easy. Use it as a demonstration or vary the amounts of citric acid and sodium bicarbonate to make an experiment.

Difficulty: Average

Time Required: Minutes

Here's How:

1. Pour the citric acid solution in a styrofoam coffee cup. Use a thermometer or other temperature probe to record the initial temperature.
2. Stir in the baking soda (sodium bicarbonate). Track the change in temperature as a function of time.
3. The reaction is: H₃C₆H₅O₇(aq) + 3 NaHCO₃(s) --> 3 CO₂(g) + 3 H₂O(l) + NaC₆H₅O₇(aq)
4. When you have completed your demonstration or experiment, simply wash the cup out in a sink. No toxic chemicals to mess with!

Tips:

1. Feel free to vary the concentration of the citric acid solution or the quantity of sodium bicarbonate.
2. An endothermic is a reaction that requires energy to proceed. The intake of energy may be observed as a decrease in temperature as the reaction proceeds. Once the reaction is complete, the temperature of the mixture will return to room temperature.

What You Need:

• 25 ml citric acid soln
• 15 g baking soda
• styrofoam cup
• thermometer
• stirring rod