Water expands when it freezes

Read our standard health & safety guidance

Lesson Organisation

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.

Apparatus and Chemicals

Per demonstration:

Glass bottle with a lid (see note 1)
Plastic zip-lock type bag (see note 2)

Technical Notes

1 A thin walled glass bottle with a screw-top lid is ideal.

2 A thick plastic bag is best as it will need to contain broken glass. The bag needs to be see-through.

Procedure

a Fill the bottle as full as you can and attach the lid.

b Dry the outside of the bottle, place into the plastic bag and seal it.

c Put into the freezer at least overnight.

Next lesson

a 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 then the liquid. It might be worth emphasising to the students that this is an unusual property and most substances are more dense as solids than as liquids.

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.

Health & Safety checked, April 2008

Weblinks

The JESEI (Joint Earth Science Education Initiative) website has several resources for teaching Earth Science. See http://www.esta-uk.org/jesei/index2.htm

(Websites accessed April 2008)