Ice floats in water because when water is frozen, it expands and gets less dense. Anything that is less dense will float on a more dense material, such as water. Learn how Archimede's Principle explains the rules of density with information from a math and science teacher in this free video science lesson.
Hi, I'm Steve Jones, and I'm going to explain why ice floats. Well, the main reason why ice floats, is that water, when it freezes, it expands, so water expands when it turns to ice, so that means that the same weight of water, or the same mass we should say, same mass of water, takes more volume, and therefore, the density is less, so the density of ice, is less than the density of water. Now, here on the diagram, we can see we've got ice, and it's density is about .9 grams per centimeter cubed, or maybe a little bit more. It depends on the water, and water's density is 1 gram, for every centimeter cubed, therefore, as we put the ice into the water, the ice is pushing down, and this .9 grams is being balanced by the water, and the water always has that little bit extra power, to support the ice. The ice never actually gets fully in the water, so the ice will float. This is Archimedes Principle, and therefore, what we know is, that if it's less dense, it will float. Ice is formed from water. When the water freezes, the ice is formed, and it is bigger in volume, lower in density, and that is why ice floats.