Question

HELP!! Please, can someone explain what happened?
Driving off the water of hydration, the student heated the sample to a fairly uniform blue color, but at a high heat. He soon noted that the thin film of splattered material on the sides of the weighing dish and the underside of the main mass of the blue solid in the bottom of the dish started to turn gray.
What happened? What should he do?

Answer 1

I believe that the blue colored solution has reached the boiling point due to the high heat, so that is now being evaporated off

Answer 2

He should immediately turn down the heat, and only heat in a gentle/uniformed manner

Answer 3

Is there any reason for it to turn grey?
My original theory was that soot was being deporsited by the flame since the question said the grey material was appearing on the underside of the dish..

Answer 4

oh wait, I take that back. Only the inside of the dish was turning grey, not the outside. So it can't be soot

Answer 5

Waters of hydration are not chemically bonded to the remainder of the complex, so they can be driven off at fairly low heat. However, too much heat runs the risk of driving an actual chemical reaction, which would change the complex beyond just driving off the waters of hydration. For example, the sample could further oxidize, e.g. a hydroxide could be reduced to an oxide, or a carbonate to an oxide. That would explain the color change, because you would have a different compound in those regions, where the heat most thoroughly penetrated the sample (because it was thin -- the splatters -- or near the source of heat -- the bottom of the sample).

I don't know what compound you've got, so I can't advise further on the chemical reaction that could be going on. But in an oxygen atmosphere, with high heat, some kind of oxidation seems plausible.

Answer 6

I agree with that explanation ^

Answer 7

thanks guys :)