Which of the following changes represents a physical change, rather than evidenc

Question

Which of the following changes represents a physical change, rather than evidence of a chemical reaction? Why?

(A) When water and a yello solution of antifreeze are mixed, the resulting solution is a lighter shade of yellow than the original antifreeze solution.

(B) When concentrated HNO3 is placed in contact with copper metal, a brown gas is formed, the copper dissolves, and a green solution is formed.

(C) When an egg is fried, the clear part becomes white, and the egg beocmes a solid.

(D) When a piece of zinc metal is plalced in a blue solution of copper sulfate, the solution turns from blue to colorless, the zinc dissolves, and copper metal is formed.

(E) When solutions of AgNo3 and NaCl are mixed, a white solid forms.

Explanation / Answer

(A) Yellow solution lighter due to dilution. There is no change in chemical composition of compounds.

So, it is a physical change.

(B) Here, Copper metal is oxidized. The chemical nature of compound changed.

So, it is a chemical change.

(C) The structure of the proteins in egg are changed when fired.

So, it is a chemical change

(D) Zinc is oxidized here.

So, it is a chemical change.

(E) silver ion is precipitated as AgCl.

It is a chemical change.

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