Question: Why does ice float?

Emily Hayward answered on 16 Jun 2014:

Ice floats as it is less dense than water (it weighs less for the same volume). Most substances are heavier when they are solids as the bonds between molecules mean they are closer and you can fit more in, however water is an unusual substance in that when it is a solid the molecules are further apart than as a liquid meaning you fit less molecules in the same space so it is less sense. You can try this at home….if you fill up an ice cube tray so the water is level with the top of the bits that seperate the ice cubes and put it in the freezer. If you leave it overnight allowing it to freeze you will see the ice cubes are taller than the height of the water was when you put it in – this expansion is the change in density making it float.