Question

Which one of the following processes involve chemical reactions?

• A. Storing of oxygen gas under pressure in a gas cylinder
• B. Liquefaction of air
• C. Keeping petrol in a china dish in the open
• D. Heating copper wire in presence of air at high temperature

Answer 1

The correct option is D

Heating copper wire in presence of air at high temperature

The explanation for the correct option

(D) Heating copper wire in presence of air at a high temperature

Chemical reaction

• A chemical reaction is a process by which one chemical substance changes into another chemical substance.
• For example, iron rusts, coal burns, candles burn, papers burn, milk sets into cottage cheese or ghee, food digests, etc.
• A chemical change occurs during a chemical reaction because a product substance is formed that has entirely different characteristics from the original substance.

Heating copper wire in presence of air at a high temperature

• Copper $\left(\mathrm{Cu}\right)$ undergoes an oxidation process and produces copper oxide $\left(\mathrm{CuO}\right)$ when heated to high temperatures in the presence of air.
• The reaction is as follows:

$2\mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\stackrel{∆}{\to }2\mathrm{CuO}\left(\mathrm{s}\right)$

The explanation for incorrect options

• In all other options, no chemical reaction is involved.
• Hence, all other options (B), (C) and (D) are incorrect.

Therefore, the correct option is (D) Heating copper wire in presence of air at a high temperature.