Oxygen shares its two unpaired electrons with two hydrogen atoms Water’s Molecular Structure:

Electronegativity the tendency for an atom to attract electrons

Solubility Polar charges attract it to other polar molecules sugars, ionic compounds (like salt), and some proteins Not attracted to nonpolar substances like lipids (fats)

Hydrogen Bonds: Weak, polar covalent bonds. Form rapidly and break rapidly Example: Between water molecules H-Bonding explains unique properties: cohesion, adhesion, high heat capacity, evaporative cooling, the low density of ice, the ability of water to dissolve many substances

Cohesion Molecules of the same substance are attracted to each other Leads to surface tension and water droplets

Adhesion Attraction between molecules of different substances Ex: glass and water Capillarity Attraction that causes the surface of the liquid to rise when in contact with a solid.

Cohesion-Adhesion Theory -As water evaporates from leaves, it tugs on the water molecules below -Cohesion and adhesion pull water up and replace missing water molecules -Water enters the roots by osmosis Did you ever wonder: How does water move from roots to leaves when a tree doesn’t have a heart to pump the water?

Denisty of Ice Most solids are more dense than their liquids This makes solids sink Ice is less dense than liquid water Due to H-Bonds Important to life because bodies of water freeze top down Allows life to survive below

pH Scale Measurement of the concentration of hydrogen ions Acid: High concentration of [H + ] (or hydronium ion); low conc. of [OH - ] Base: High [OH - ] (a.k.a. hydroxide ion); low [H + ] pH = -log [H + ]