I noticed a whitish layer on the surface of a chocolate bar that I ate yesterday. I looked at the pack where it was mentioned that,
"Temperature and humidity changes may cause product to develop a whitish layer, without affecting its fitness for consumption. "
My first doubt is, is this a chemical or physical phenomenon? if it is chemical process, please elaborate.
It is solid cocoa butter, that may get "sweated" to the surface and solidified later. It can be caused by long term temperature fluctuations, or just effect if time.
So it is mainly the reversible fat phase transitions (bordering chemical and physical as non chemical change) and matter redistribution.
If you insist, you can consider it as a physical change, as substances did not transform to something else.
Or, it could be a chemical change two, as the are several forms of solid cocoa butter and transition between them can be considered as chemical change.
All chemical phenomena are physical phenomena too, as chemistry is part of physics that physicists left for chemists. The boundary between these domains is not sharp and it sometimes does not make much sense to insist on categorization.
