Endothermic reactions

Use it as a demonstration or vary the amounts of citricacid 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: H 3 C 6 H 5 O 7 (aq) + 3 NaHCO 3 (s) → 3 CO 2 (g) + 3 H 2 O(l) + Na 3 C 6 H 5 O 7 (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 beobserved 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