Need list of common endothermic reactions

[peterpacz1]

Hello there, it is my first day on these forums today.

 

I am planning a science fair project to do, (a real science lab, with variables and data collection, not just a "demonstration"). I am basically measuring the cold produced by different endothermic reactions, such as adding salt on ice for example. It would be nice if the forum commenters could list a few common endothermic reactions that I would be able to produce using common or household materials, or chemicals commonly avalable inside a labortory. Please note that I am merely 13 years old, so please list chemicals by their names rather then symbols.

Thank you very much, and if this is in the wrong section, i will apologise in advance. This may seem a bit like homework help, but i thought it belongs more in the chemistry section.

[Enthalpy]

Welcome here!

 

Mix of water with glycerine, with erythritol, xylitol

http://en.wikipedia.org/wiki/Erythritol

http://en.wikipedia.org/wiki/Xylitol

available commercially, used in food for the "refreshing" effect in contact with mouth water.

 

Water ice can also be mixed with ethanol, or methanol, to produce cold. Beware methanol is a poison (and ethanol as well, in fact).

[peterpacz1]

Isn't ethanol grain alcohol, and methanol wood alcohol? I read about them in a book about the Prohibition before, i think. (Apparently, when they banned alcohol in the United States during 1920 and 1933, and during that time some people got so desperate for alcohol and drank methanol, which ruined their liver and health).

Also, do you know how much of a temperature change would be induced in that reaction? I would need something that is fairly measurable on electric thermometers of suspicious quality that are available in my school.

[Enthalpy]

Mix of water with glycerine, erythritol or xylitol is cold to the hand, so if your thermometer doesn't show it, just forget any thermometer.

 

And ethanol with ice produces something like -40°C so it's not a matter or hypersensitive instruments.

 

Ethanol, methanol : yes, that's it.

[ajkoer]

OK, burning a Mg ribbon in O2 (caution, very hot reaction temperature and blinding light) is an example of a highly exothermic reaction with a very stable compound Magnesium oxide, MgO, forming. In air, mention that Mg3N2 is also formed, which liberates NH3 with water (a possible fuel source).

 

 

3 Mg + N2 + 461 kJ/mol --> Mg3N2

 

Mg + 1/2 O2 + 601 kJ/mol --> MgO

 

Mg3N2 + 6 H2O ---> 3 Mg(OH)2 (s) + 2 NH3 (g)

 

Reacting purple Iodine vapors (from gently heating I2 at one end of a flask) with NH3 fumes, should procedure a red smoke in a flask. This is an example of an endothermic reaction (show condensation). It forms a very unstable and highly sensitive novelty explosive 8 NI₃ · NH₃ (only demo in very small amounts).

 

24 I2 (s) + 9 NH3 (g) + Heat → (8NI3. NH3) (s) + 24 HI (g)

 

2 NI₃ (s) → N₂ (g) + 3 I₂ (g) (–290 kJ/mol)

 

Dry salt deconposing:

 

8 NI₃ · NH₃ → 5 N₂ + 6 NH₄I + 9 I₂

 

If the flash, bang, all the equations and talk of green fuel does get the judges all excited, I don't know show business.

Edited April 23, 2013 by ajkoer