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I have a summer job as a custodian and one cleaner I use is called Goof Off, which is pretty much just acetone. Another is a disinfectant which is mostly water.

Why is it that whenever I put the acetone on my rag, it is always colder than when I use another cleaner or plain water?

The acetone also seems to stay cold longer than water does. Both cleaners are left in the open so they are both the same temperature.

Melanie Shebel
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Ryan
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    Acetone is significantly more volatile than water. When you pour it onto a rag, it begins evaporating, taking some of the heat with it as it does so hence why it appears slightly cool – NotEvans. Jul 27 '16 at 16:43
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    Evaporative cooling is also the exact purpose of sweating. Too bad we don't sweat acetone, would be handy on a hot day (although we'd probably be re-painting a lot of things...) – Jason C Jul 27 '16 at 21:51
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    Goof-off superglue remover is acetone. Their other adhesive remover is ethylene glycol; basically antifreeze. – Eric Lippert Jul 28 '16 at 06:38

1 Answers1

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Evaporation is an endothermic phenomenon, i.e. it absorbs heat in order to proceed. Acetone is a volatile solvent (it evaporates easily) so it absorbs much heat when evaporating, and your skin gets colder because of that. That is what you are feeling. So acetone is not "colder", it just cools down your skin more easily when evaporating.

Ether (aka diethyl ether) is even more powerful at this.

On another note, while acetone is a pretty safe solvent, it can damage your skin because it can take away skin's lipids and you get "dry hands". In France, your employer would be forced to provide you with protecting gloves, e.g. latex gloves.

SteffX
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    On a Good News™ note: Acetone isn't so bad, compared to some cleaning solvents in active use. – Williham Totland Jul 27 '16 at 19:42
  • In active use in countries that don't mandate basic security gear like rubber gloves, that is. – Williham Totland Jul 27 '16 at 19:43
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    (With suitable fire precautions and ventilation) dip a thermometer wrapped in a rag into some room temperature acetone. I bet you will see the temperature drop as the acetone starts to evaporate. So while SteffX is correct that the cold feeling on your skin is because heat is drawn quickly from your skin, the acetone is actually colder. http://highschoolenergy.acs.org/content/hsef/en/how-can-energy-change/energy-of-evaporation.html – dcorking Jul 28 '16 at 07:50
  • @dcorking But StellX states clearly that the "skin gets colder because of [the evaporation]". – Crowley Jul 28 '16 at 11:43
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    @Crowley Yes, the answer is great, because the lower temperature, and the sensation of cold skin, are both caused by evaporation. My only concern is with this sentence, 'So acetone is not "colder", it just cools down your skin more easily when evaporating,' which is not precisely correct. – dcorking Jul 28 '16 at 13:31
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    I think that it was meant that "if you pour your hand with water and acetone both with same temperatures, the acetone will cool your hand faster (easier)". Nevertheless, the sentence is not written well. – Crowley Jul 28 '16 at 13:39
  • Acetone is never let evaporating in a large piece of glassware in real life. It is most usually stored in a wash bottle and evaporation is very limited. Original question was about the difference between washing with water and acetone. Hence my answer. – SteffX Jul 28 '16 at 14:54
  • @dcorking No, the acetone is NOT colder. The fact that the thermometer would suffer a drop in temperature is due to the evaporation and the fact that the thermometer suffers first from the endothermic process. It will then exchange with the rest of the air in a slower manner and be at equilibrium. If you do the experiment in conditions where evaporation is not possible (close to the fusion point -94.6°C for instance), then the thermometer will not suffer from any temperature drop. – Martigan Jul 28 '16 at 15:16
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    @Martigan exactly: any liquid that is adiabatically evaporating will get colder. – dcorking Jul 28 '16 at 15:25