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

Some useful examples of Exothermic reactions

What are some examples of exothermic and endothermic processes?
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I a student looking for common and not so common occurances of endothermic and exothermic processes. I am trying to achieve an understanding of this occurances to be able to recognize them myself. Thanks.
Terry Holbrook
When trying to classify a process as exothermic or endothermic, watch how the temperature of the surroundings changes. An exothermic process releases heat, and causes the temperature of the immediate surroundings to rise. An endothermic process absorbs heat and cools the surroundings. Can you think of a way to test the classification of each of these processes?
Exothermic processes Endothermic processes
making ice cubes melting ice cubes
formation of snow in clouds conversion of frost to water vapor
condensation of rain from water vapor evaporation of water
a candle flame forming a cation from an atom in the gas phase
mixing sodium sulfite and bleach baking bread
rusting iron cooking an egg
burning sugar producing sugar by photosynthesis
forming ion pairs separating ion pairs
Combining atoms to make a molecule in the gas phase splitting a gas molecule apart
mixing water and strong acids mixing water and ammonium nitrate
mixing water with an anhydrous salt making an anhydrous salt from a hydrate
crystallizing liquid salts (as in sodium acetate in chemical handwarmers) melting solid salts
nuclear fission reaction of barium hydroxide octahydrate crystals with dry ammonium chloride
mixing water with calcium chloride reaction of thionyl chloride (SOCl 2 ) with cobalt(II) sulfate heptahydrate



An example of an exothermic reaction is the mixture of sodium and chlorine to yield table salt.This reaction produces 411 kJ of energy for each mole of salt that is produced:
Na(s) + 0.5Cl 2 (s) = NaCl(s)
Demonstrations You Can Perform
Many exothermic and endothermic reactions involve toxic chemicals, extreme heat or cold, or messy disposal methods. These demonstrations are safe and easy:


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