[hunterxv]

hey!

We did an experiment where a spiral/helix of Cu was heated up and then it was cooled down by itself.
Then we did the same thing again, but this time we placed the Cu over a container of NH3(aq), resulting in a faster cooling. Can anybody explain why the Cu can be cooled down faster when it is placed over a container with NH3?
 

[miaskows]

When you mentioned "cooled down by  itself" what have  you meant? Was it cooled down in an open air? If the difference between two experiment were the mediums, your  Cu helix has transfered it's heat for, then the problem is not of chemical character but rather of thermodinamicl one. Heat transfer coefficient (responsible for rate of heat transfer )between solid and gas much more lower than between solid to liquid.
Also, concentrated solutions of NH3, when heated could evolve gaseous NH3 and it could  ,in some extent,  help for cooling.

[hunterxv]

Yes by itself, or to be precisly in a fume cupboard.
The amount used was 30ml of concentrated NH3.

So you could say there's no chemical formula here, only heat transfer?

[miaskows]

Strongly heated Cu can react with NH3 to form Cu3N, but it unlikely would be the reason for it's faster cooling ( probably  for some colorization of Cu surface only)
Immersing of very hot solid body in to concentrated water NH3 would cause it's desorbtion from the solution. It is endotermic process. It would also be reason for fast cooling of the helix.