Testing for products of combustion

We set out to prove that water is made when you burn a fuel. the problem is that it is in the form of water vapour and you can't see it. So we used a beaker of ice to make the water vapour condense on the outside. We used anhydrous cobalt chloride paper, which is blue. It turns pink when it touches water. There's our proof. The colour change must be related to a change in the electron energy bands on accepting water into the molecule.