Liquid Water Is Denser than Ice

Liquid Water Is Denser than Ice
Kinetic molecular theory, which we cover in Chapter 10, predicts that adding heat to a collection
of particles
increases
the volume occupied by those particles.
Heat-induced changes
in
volume are
particularly
evident at phase changes, so liquids tend to be less dense than
their
solid counterparts.
Weird
water throws
a wet monkey wrench
into the works. Because
of
H
O’s ideal hydrogen-bonding geometry, the lattice geometry of solid water (ice) is very
“open,” with large, empty spaces at the center of a hexagonal ring of water molecules. These
empty spaces lead to a lower density of solid water relative to liquid water, so ice floats in
water. Although annoying, this watery exception is quite important for biology.
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