Question

How do water’s relative densities as a solid and a liquid differ from that of most other substances?

Answer 1

so water as a solid (aka ice) is actually less dense than water as a liquid (regular, liquid water). this is bc there is a specific and repeating pattern to ice amongst the hydrogen and oxygen molecules; the space in between means the atoms are less concentrated. other substances have a denser solid form

Answer 2

Solid water is less dense than liquid causing it to float while other substances are mainly more dense as solids.