Question

Which one of the following is a pure substance?

• A. Soft drink
• B. Salt water
• C. Muddy water
• D. Sugar crystals

Answer 1

The correct option is D Sugar crystals

A pure substance consists of only a single type of particle - atoms or molecules. Pure substances are classified as elements and compounds.
Sugar is a pure substance as it is made up of only one kind of molecule which is the sugar molecule $\left({\text{C}}_{12}{\text{H}}_{22}{\text{O}}_{11}\right)$.

The other options salt water, muddy water, and soft drink are not pure substances because these are mixtures and contains more than one type of particles.