Question

In which of the following process new substance(s) are formed?

• A. Melting of ice
• B. Sublimation of naphthalene
• C. Photosynthesis
• D. All of these

Answer 1

The correct option is C

Photosynthesis

Explanation of correct option:

(C):

• Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar $\underset{\mathrm{carbon}\mathrm{dioxide}}{6{\mathrm{CO}}_2}+\underset{\mathrm{water}}{6{\mathrm{H}}_2\mathrm{O}}\stackrel{\mathrm{sunlight},\mathrm{chlorophyll}}{\to }\underset{\mathrm{glucose}}{{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6}+\underset{\mathrm{oxygen}}{6{\mathrm{O}}_2}$
• This is a chemical and irreversible change considering the above equation, where new substances are formed, glucose and oxygen

Explanation of incorrect option:

(A): Melting of ice is a physical and reversible change heat removed from water converts it to ice and heat added to ice converts it to water, $\mathrm{Ice}\left(\mathrm{s}\right)\underset{\mathrm{Freezing}}{\overset{\mathrm{Melting}}{\rightleftharpoons }}\mathrm{Water}\left(\mathrm{l}\right)$

(B): Sublimation is the conversion of a substance from the solid to the gaseous state without its becoming liquid. This is also a reversible change as the conversion of these vapors to solid is known as deposition, Naphthalene undergoes the same.

Hence, option (C) is correct