A student placed equal volumes of honey and of water in two, identical, open dishes, and left them at room temperature for 8 hours. She observed that the amount of water decreased, but the amount of honey seemed unchanged. Knowing that honey is a highly concentrated solution of sugar in water, which statement should the student make to explain this phenomenon?
Answer
H
Honey has a much lower vapor pressure than pure water has. So, pure water evaporates at a much higher rate.
H
Honey has a much higher vapor pressure than water has. So, water evaporates at a much higher rate.
H
Honey has a much lower freezing point than water has. So, water evaporates at a much higher rate.
H
Honey has no vapor pressure. So, water evaporates at a much higher rate.
Explanation
Dissolved sugar lowers the vapor pressure of water in honey compared with pure water. Because fewer water molecules escape from the honey’s surface into the air, honey evaporates much more slowly, while the pure water level decreases. Thus, the correct statement is that honey has a much lower vapor pressure than pure water.
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