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

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.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: