3.4
WATER PROPERTIES
Does water expand or contract
when it freezes?
Activity Time: 20 minutes
Background
Why does water expand when it’s frozen? Water molecules are attracted to one another and
stick together or bond when they get close enough. The molecules have spaces between them
and the spaces change depending on their temperature. Liquid molecules are more flexible and
can crowd together, making them take up less space or volume. As the temperature gets colder,
the molecules form a hexagonal structure that is not flexible and takes up more space than the
same number of liquid molecules.
Materials
Per Group:
Small piece of clay
1 small jar
Blue food coloring
1 permanent marking pen
1 spoon
1 metric ruler
1 straw
Directions
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Press the piece of clay inside on the center of the bottom of the jar.
Pour tap water into the jar until it is almost full.
Add 4 drops of food coloring and stir.
Lower the straw slowly into the water.
Push the straw into the clay so it is standing.
Slowly pour all of the water out of the jar, keeping the water in the straw by placing your finger
on the top.
Mark the height of the water in the straw with the pen.
Freeze the jar overnight.
Measure the change in the height of the ice.
Assessment
Complete Assessment 3.4: Does water expand or contract when it freezes?
Extension
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How else can you prove that water expands when frozen?
Design an experiment and share the results with the class.
Related Activities
Why does ice float? (3.2)
Why does this magic trick
work? (3.5)
Vocabulary
Expansion: growth or spreading
out.
Liquid: a substance that flows
whose shape can be changed but
not its volume.
Volume: the size of a threedimensional space enclosed
within or occupied by an object.
ALIGNMENT TO NGSS:
Scientific and Engineering Practices
•Asking questions
•Planning and carrying out
investigations
•Constructing explanations
•Engaging in argument from
evidence
•Obtaining, evaluating, and
communicating information
Crosscutting Concepts
•Cause and effect
•Stability and change
Disciplinary Core Ideas
•K-5: PS1.A
•6-8: PS1.A