Question

Which process is a chemical change?
A.Dissolving copper (II) sulphate
B.Distilling ethanol
C.Freezing water
D.Neutralizing copper (II) oxide

Answer 1

Hint: Chemical change refers to the change in which the molecular composition is completely altered and a new product is formed. Moreover, these changes are irreversible and permanent which means these changes cannot be reversed by changing or altering the experimental changes.

Complete step by step answer:
-Some changes are periodic while others are non-periodic. Some are reversible while others are irreversible. So, on a larger front, a change may be categorized as chemical change or physical change depending on how the properties of a subject alter when it undergoes the change. So let’s discuss both the changes.
-Physical change- A substance is said to undergo a physical change when only the physical properties such as color, size, shape or appearance of the substance changes. Moreover, these changes are temporary in nature and no new substance is formed. For example folding of a paper sheet, melting of ice, dissolving sugar in water etc.
-Chemical change- A substance is said to undergo chemical change when the chemical properties of a substance alter. So, there is either formation or breaking of atomic bonds at the molecular level. These changes are permanent in nature and new substances are formed. For example rusting of iron, burning of paper, cooking etc.
-Now, among the given options neutralizing copper (II) oxide is a chemical change because as the compound reacts with a dilute acid, the formation of a soluble salt takes place. The reaction is as shown:
 $CuO + {H_2}S{O_4} \to CuS{O_4} + {H_2}O$

Hence, option D is correct.

Note:
There are some substances that show both the changes like burning of candle is both a physical as well as a chemical change. The burning of candle is a chemical change whereas conversion of the candle to wax is a physical change.