Chapter 12, Problem 89A

Interpretation Introduction

Interpretation:

On dissolving sugar crystals in water, a clear homogeneous mixture is formed. If the solution is left out at room temperature after some time (few days) crystals start to reappear. Whether the reoccurring is an example of freezing or not needs to be explained.

Concept introduction:

When a supersaturated solution is formed, no more solute gets dissolved in the solvent and it gets settled down at the bottom of the container.

Explanation of Solution

When sugar is dissolved in water to form a homogeneous mixture and it is left for a few days at room temperature, the reoccurrence of sugar crystals is not freezing. The only process that takes place is the evaporation of water. Due to this, the sugar to water ratio in the solution changes and the amount of sugar starts increasing. A supersaturated solution is formed at a stage and further evaporation of water causes crystallization of sugar as sugar cannot be in dissolved form in that less amount of water.