Which of these changes involved a physical change and not a chemical change?

In a laboratory experiment, a fermenting aqueous and produces dioxide gas and ethanol. The heated by burning natural gas in a Bunsen burner to ethanol formed in the flask. During the distillation, the ethanol evaporated and then condensed in the receiving flask. The flame of the bumer was kept too close to the bottom of the flask and some of the glucose decomposed into a black carbon deposit on the inside of the flask. During this experiment the following changes occurred.

1 Answer
Sep 2, 2016

Answer:

As far as I can see, the distillation was the only instance of physical change.

Explanation:

Chemical change is characterized by the making and breaking of strong chemical bonds, and the formation of new substances. Clearly, during the fermentation, sugars reacted chemically to give carbon dioxide gas and ethanol, an unequivocal chemical change. The glucose decomposition was also an example of chemical change; so too was the hydrocarbon combustion, which gave water and carbon dioxide from methane and oxygen.

On the other hand, physical changes are mostly changes of state. The distillation and condensation, liquid to gas to liquid, are certainly instances of physical change.