Ice Floats: The Anomaly
Explore density and anomalous expansion of water
Setting up the bench…
What this lesson covers
Why it matters
Most substances sink when they freeze, but ice cubes float in your glass. This strange behavior keeps lakes from freezing solid in winter.
Predict first
Why does ice float on liquid water?
Water expands when it freezes, making solid ice less dense than the liquid it came from.
- Ice is less dense than liquid water — correct
- Ice is lighter because it has less mass
- Ice is more dense than liquid water
- Air bubbles trapped in ice make it float
What you do
Arrange from most dense to least dense. The answer explains why lakes freeze from the top — and why ice floats in your glass.
Check yourself
What happens to the volume of water when it freezes?
Water expands upon freezing due to the open hexagonal structure of ice.
Why does ice have a lower density than liquid water?
In ice, hydrogen bonds lock water molecules into a spacious hexagonal arrangement, increasing volume and decreasing density.
- It decreases
- It increases — correct
- It stays the same
- Hydrogen bonds hold molecules in a rigid, open lattice — correct
- The molecules shrink when cold
- The molecules move faster in ice
- Ice molecules are individually heavier than liquid water molecules