Question

How does waters relative densities as a solid and a liquid differ from that of most other substance

Answer 1

Water has a lower density as a solid than it does as a liquid.

Answer 2

Under normal ambient conditions water is less dense as a solid than as a liquid, so ice floats on water. Most materials are more dense as solids.

Water has a lower density as a solid than it does as a liquid. In the vast majority of substances are denser as solids than as liquids.