Water is unusual in the fact that when it freezes it expands. Most other liquids contract when freezing. This practical demonstrates that water expands when it freezes and also shows to what extent it expands.
This practical gives an explanation as to why water pipes sometimes burst in cold conditions and how rocks can be broken apart in the freeze-thaw process.
Equipment required (per demonstration):
- Glass bottle (preferably thin glass) with screw lid
- Sealable plastic freezer bag
Fill the bottle up to the brim with water and firmly screw the lid on tight. Place in the sealable bag and into a freezer.
During freezing the water inside the bottle will expand and either break the bottle or break the cap off. The bottle can be placed in a sealed clear plastic box and shown to the class.
The freeze-thaw principle occurs where water is trapped in a rock crevice. As the water freezes, it expands, pushing the rock apart. This principle is a form of rock weathering.
Another way to show the expansion is to fill a measuring cylinder with water and check the level. When the water is frozen you should be able to see a noticeable difference in volume within the cylinder.