Water

Properties of water

Outline

Properties of Water

Properties of Water

High b.p., m.p., heat of vaporization, surface tension

Bent structure makes it polar Non-tetrahedral bond angles H-bond donor and acceptor Potential to form four H-bonds per water

Comparison of Ice and Water

Issues: H-bonds and Motion Ice: 4 H-bonds per water molecule Water: 2.3 H-bonds per water molecule Ice: H-bond lifetime - about 10 microsec Water: H-bond lifetime - about 10 psec

Solvent Properties of Water

Ions are always hydrated in water and carry around a "hydration shell"

Water forms H-bonds with polar solutes Hydrophobic interactions - a "secret of life"

Hydrophobic Interactions

A nonpolar solute "organizes" water The H-bond network of water reorganizes

to accommodate the nonpolar solute This is an increase in "order" of water This is a decrease in ENTROPY

Amphiphilic Molecules

Also called "amphipathic" Refers to molecules that contain both

polar and nonpolar groups Equivalently - to molecules that are

attracted to both polar and nonpolar environments

Good examples - fatty acids