How To Create an Endothermic Chemical Reaction (Safe)

How To Create an Endothermic Chemical Reaction (Safe)

By Anne Marie Helmenstine, Ph.D., About.com
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

From: about.com