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Chemical reaction & cooling

  1. Jul 22, 2005 #1

    i am not chemist, and i am looking for some simple reactions which can happen at room temperature and it creates cooling after reaction, i.e. it absorbs energy.

    any body know some examples? :confused:

  2. jcsd
  3. Jul 23, 2005 #2
    You are looking for an endothermic reaction, I think?
    I guess the simplest reaction I can think of is ice --> water :P

    A relatively more complex one might be the reaction of citric acid and baking soda

    I will sketch out the endothermic reaction for you

    H3C6H5O7 (aq) + 3NaHCO3 (s) --> 3CO2 (g) + 3H2O (l) + NaC6H5O7 (aq)

    Forgive my lack of tidiness and Latex :P
  4. Jul 23, 2005 #3


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    Are you specifically looking for a chemical reaction ? Most evaporations at room temperature will do what you want - except they are not considered chemical reactions. Examples : evaporation of water, methanol, acetone, isopropanol.

    A popular room temperature reaction that is highly endothermic is that between hydrated barium hydroxide and ammonium thiocyanate. Mixing a couple of spoonfuls (okay, spatulafuls) of each can cool the beaker below freezing in a matter of seconds.
  5. Jul 23, 2005 #4
    what is the chemical formulae for ammonium thiocyanate? i never heard it.

    is barium hydroxide BaOH ?

    sorry, i really don't know chemistry.
  6. Jul 23, 2005 #5
    no need to reply. i found the formulae.\

  7. Jul 23, 2005 #6
    Dissolve some ammonium nitrate in water and you've got a cold pack.
  8. Jul 23, 2005 #7
    but if i buy that i will be suspect for terrorist.
  9. Jul 23, 2005 #8
    What do they use in those air cans that they use to clean computer key boards with? After you start to use it, the can beceome extremely cold and frost build up on it.
  10. Jul 23, 2005 #9
    oh yes, of course how could I forget? if you put the barium hydroxide and ammonium cyanate in a beaker that's on top of a wooden board with a some liberally sprinkled water on it, you can easily have it frozen to the board for a dramatic effect =)
  11. Jul 23, 2005 #10


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    I thought that was just pressurized air in the can. The cooling would be from the Joule-Thompson expansion of the compressed gas.
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