Thread: Why does ice float on water ?

Anyone can give me an explanation on why ice is less dense than water ? Thanks !

Check out this link for a definitive answer. Why Does Ice Float?

When water freezes, micro bubbles of air get trapped within the ice crystals [ this is the gas they examine in ice cores from long ago ]
making it less dense. Obviously the 3rd of waters 'triple states' is steam which is less dense again.

Most substances become more compact when colder -water is an exception.

Originally Posted by tszy

When water freezes, micro bubbles of air get trapped within the ice crystals [ this is the gas they examine in ice cores from long ago ] making it less dense.

Ice would be less dense than water even without trapped air. In fact, as those air bubbles must have come out of solution, they affect the water equally and are therefore irrelevant.

Water becomes less dense as it freezes into ice. Since the ice is less dense than the water, it floats. The same concept applies to pool floaters. The floaters are (usually) inflated with air, they are less dense than the water, and therefore they float.

Water crystallizes as it freezes. The crystal has a lower density than the raw material it's made from.

That's also one of the reasons you can't freeze a human being without killing them.

Water is one of very few substances whose solid is less dense than its liquid. In essence, a liquid is simply an enormous amount of atoms/molecules jumbled together, constantly spilling over each other in an effort to reach their lowest energy state. When most liquids freeze, their atoms (or molecules) combine in the form of a crystal, which is an ordered, compact array of these particles. Usually, particles combined in this way are less dense than liquids, as they fill every space efficiently. An analogy is if you were to throw several hundred balls into a box, they could be disorderly, like a liquid. Unnecessary gaps could exist between the balls, taking up extra space and allowing fewer balls to fill the box. However, if you were to shake the box (representative of becoming a solid), the balls would form a pattern and you could fit more of them into the space (more dense).

Water is different. The water molecule is small and very polar, so its crystallization is different than most substances. In fact, water molecules form intricate, nearly circular patterns in crystallization. These patterns take up more space than liquid water, allowing it to float because it is less dense!