Water Expands When It Freezes | Experiment - RSC Education

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Water expands when it freezes

In association with Nuffield Foundation

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Demonstrate that water expands when it freezes by showing how it can break a bottle

In this practical, students observe what happens when a bottle is filled with water and allowed to freeze. The water expands as it freezes, which breaks the bottle. This is useful when teaching about the weathering of rocks and freeze-thaw.

This demonstration can be set up in one lesson and left in the freezer until the next. The demonstration itself takes only a few minutes.

Equipment

Apparatus

• Glass bottle with a lid (see note 2 below)
• Plastic zip-lock type bag (see note 3 below)

Chemicals

• Water

Health, safety and technical notes

1. Read our standard health and safety guidance.
2. A thin-walled glass bottle with a screw-top lid is ideal.
3. A thick plastic bag is best as it will need to contain broken glass. The bag needs to be see-through.

Procedure

Lesson 1

1. Fill the bottle as full as you can and attach the lid.
2. Dry the outside of the bottle, place into the plastic bag and seal it.
3. Put into the freezer at least overnight.

Lesson 2

Remove the bag from the freezer and observe the broken bottle.

Teaching notes

This demonstration shows the very unusual property which water has of expanding when it freezes. In the liquid state water molecules can pack more closely together than in the crystal structure of ice. This means the ice is less dense and so takes up more space than the liquid. It might be worth emphasising to the students that this is an unusual property and most substances become more dense as solids.

This property contributes to the physical weathering of rocks. Rocks which absorb water and then freeze can be broken down as the water expands.

The broken bottle can be put back into the freezer and used again later to show to another class.

Additional information

This is a resource from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry.

Practical Chemistry activities accompany Practical Physics and Practical Biology.

© Nuffield Foundation and the Royal Society of Chemistry

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Level

• 11-14 years
• 14-16 years

Use

• Demonstrations

Category

• Properties of matter
• Structure and bonding

Specification

• Scotland
  • Higher
    • SQA Chemistry
      • 1. Chemical changes and structure
        • (b) Structure and bonding
          • (ii) Intermolecular forces
            • Hydrogen bonding between molecules in ice results in an expanded structure that causes the density of ice to be less than that of water at low temperatures.
• Wales
  • A/AS level
    • WJEC Chemistry
      • Unit 1: THE LANGUAGE OF CHEMISTRY, STRUCTURE OF MATTER AND SIMPLE REACTIONS
        • 1.5 Solid structures
          • (c) structures of iodine and ice
• Republic of Ireland
  • Leaving Certificate
    • Chemistry
      • 2. Chemical bonding
        • 2.3 Covalent Bonding
          • Depth of treatment
            • Characteristics of covalent substances.
        • 2.5 Shapes of Molecules and Intermolecular Forces
          • Depth of treatment
            • Distinction between intramolecular bonding and intermolecular forces. Intermolecular forces: van der Waals', dipole-dipole, hydrogen bonding.
  • Junior Cycle
    • Science
      • Chemical world
        • Building blocks
          • 2. Develop and use models to describe the nature of matter; demonstrate how they provide a simple way to to account for the conservation of mass, changes of state, physical change, chemical change, mixtures, and their separation.

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