/sci/ - Science & Math

>What is it about water that makes it expand when it's cold
The structure of the water molecule makes it form a crystal lattice that consists of water molecules that each has a double bond to adjacent water molecules (4 bonds in total for each molecule). This causes the water molecules to pack neatly into a crystal structure, but leaves "gaps" which could've been filled by other water molecules in less "ordered" conditions.
(see pic)

>am I right in thinking nothing else does this?
No.

>Secondly, as ice floats on water, this implies that ice is lighter than water? Is this just because it's expanded and so has a larger surface area? Or does it actually lose mass?

>lighter
Nope.
It's less dense than water.