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Difficulty: MediumProperties of Matter

A technician places a 500 g500\text{ g} sample of liquid water into a sealed, airtight chamber and cools it until it freezes completely into solid ice. Which of the following statements correctly describes the changes in the sample's mass and volume?

  1. A
    The mass increases because solid ice is heavier than liquid water, while the volume remains constant.
  2. B
    The mass remains unchanged, but the volume decreases as the molecules pack closer together.
  3. The mass remains unchanged, but the volume increases due to the expansion of water upon freezing.Answer
  4. D
    The mass decreases because freezing triggers a chemical reaction that consumes matter, reducing the volume.

Answer

The mass remains unchanged, but the volume increases due to the expansion of water upon freezing.
Freezing is a physical phase change that does not alter the chemical identity or quantity of matter in a closed system, so mass is strictly conserved at 500 g500\text{ g}. Unlike most liquids that contract upon solidifying, water uniquely expands upon freezing due to hydrogen bonding forming a spacious hexagonal crystal lattice, causing its volume to increase.

Step-by-Step Solution

1
Evaluate the effect of freezing on the sample's mass in a sealed system.
The mass remains exactly 500 g500\text{ g}.
According to the Law of Conservation of Mass, the total quantity of matter in a closed system cannot change during a physical phase change.
2
Determine the effect of crystallization on the volume of water.
The volume of the water sample increases.
Water exhibits anomalous expansion upon freezing; hydrogen bonding locks water molecules into an open hexagonal lattice that takes up more space than the liquid phase.
3
Combine the mass and volume findings to identify the correct physical behavior.
Mass is conserved while volume increases (and density decreases).
Freezing is a physical process where mass stays constant while the physical arrangement of molecules increases the overall volume.

Key Concept

Conservation of mass during physical phase changes and the anomalous expansion of water upon freezing.
Estimated Time:1m 0s
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Topics

Properties of Matter

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