An aqueous solution of glycerol is described as freezing at a lower temperature than pure water. Which of the following statements matches this behavior?

• A. Boils at the same temperature as that of water
• B. Boils at a lower temperature than that of water
• C. Freezes at a lower temperature than that of water
• D. Freezes at a higher temperature than that of water

Answer: (C)

This item tests how adding a solute to water changes its freezing point. When glycerol is dissolved in water, the solution contains more particles than pure water. These dissolved particles interfere with the orderly formation of the ice crystal, so the liquid must be cooled further to reach the solid phase. This is freezing point depression, a colligative property. Because glycerol is nonvolatile, the solution would also have a higher boiling point, but what’s observed here is the lower freezing point. Therefore, the statement that the solution freezes at a lower temperature than pure water matches the behavior.