Is heating CuSO4 5H20 a chemical change or a physical change and why?
In our lab, we heated copper sulfate pentahydrate (Cuso4 H20) after grinding it. Our observations included a color change from blue to white, which led us to believe it was a chemical change. When cooled, the powder turned to a blue liquid with some visible white powder at the bottom of the test tube. That is a state change which would indicate a physical change. Please explain if this is a chemical or physical change. Thank you!
This is an example of a physical change. Copper sulfate is a very hygroscopic material. This means that it absorbs and coordinates with water very readily. Note that this coordination with water is not a chemical bond formed between the copper and the water. Copper sulfate pentahydrate is a blue solid but when you heat it you evaporate the water from the sample and are left with anhydrous copper sulfate (no water present) which is white in color. Upon cooling, the white copper sulfate absorbs water from the atmosphere to become the pentahydrate again. Also, when you added water the last of the anhydrous material converted to the pentahydrate. Since no chemical bonds were broken or formed (the definition of a chemical change), this is an example of a physical change.
EDIT: The white powder turned back to blue after adding water.