Question

Select the correct answer from the choices A, B, C, and D which are given. Write only the letter corresponding to the correct answer.

Which is an example of a physical change.

• A. Metal rusting
• B. Silver tarnishing
• C. Water boiling
• D. Paper burning

Answer 1

The correct option is C

Water boiling

Explanation for correct option:

Option C

Physical change:

• A physical change is a change in which no new substance is formed.
• A physical change is temporary and reversible.
• In physical change the chemical composition of the original substance is not altered.
• For example, drying of wet clothes, breaking of a glass tumbler, drying paints, boiling of water, etc.
• During the boiling process, only the state of liquid changes.

Therefore, option C is correct.

Explanation for incorrect option:

Option A

Chemical change:

Option A

• A chemical change is a permanent change in which new substances are formed.
• The chemical change is permanent and cannot be reversed by a simple physical method.
• A chemical change involves an exchange of energy in the form of heat or light.
• Rusting of metal is a chemical change.
• During rusting, a metal corrodes gradually in the presence of oxygen and moisture and forms an oxide layer over the surface of the metal.
• During this process, a new substance is formed that is rust (${\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}$).

Therefore, option A is incorrect.

Option B

• When silver is exposed to sulfur-containing gases in the air, it discolors and then darkens as it reacts with the gas to form a surface layer of tarnish.
• This process is called tarnishing.
• During this process, new substances are formed. Hence option B is incorrect.

Therefore, option B is incorrect.

Option D

• Burning or combustion is a chemical change.
• During combustion, new substances are formed.
• Combustion is the process where a substance burns in the presence of oxygen, giving off heat and light.

Therefore, option D is incorrect.

• Hence correct Option is C