1. MODERN BIOLOGY
Ch. 2.3
Water, Solution, pH

2. Polarity: “Electron hogs and electron weaklings”
In covalent bonds where the “sharing” is unequal (like in water).
This creates a shift in the electron cloud around the stronger atom making it partially negative (-).
The shift also partially exposes the proton of the hydrogen making the hydrogen areas partially positive (+).
This makes water a polar (think of the + and – poles on a magnet) covalent (shared valence electrons) molecule.

3. Solubility of Water:
The polar nature of water allows it to dissolve polar substances (sugars), ionic compounds (salts), and some proteins.
Water does not dissolve nonpolar molecules (no poles / equal sharing: like O2).
“Like dissolves like.”

4. Hydrogen Bonding ( opposites attract too.)
The force of attraction between the + area of one molecule and the - area of neighboring molecules.
Hydrogen Bonding accounts for the unique properties of water.
cohesion: water sticks to itself (a glass of water fuller than full.)
adhesion: water sticks to other things (meniscus)
temperature moderation or the ability to absorb and release large amounts of heat with only slight changes in its own temperature:
moderation between day / night
summer / winter
coastal vs. inland climates
global moderation 
evaporative cooling
density of ice

5. Solutions Solute into solvent makes a solution.
Salt in water makes a salt solution.
Alcohol in water makes a solution.
(Solvent: whichever is in greater quantity)
Concentration: the amount of solute in a volume of solvent.
2g salt diluted up to 100 ml with water = 2% salt solution
saturated solution: no more solute can dissolve.
Aqueous solutions: water is the solvent

6. Acids and Bases
Ionization of Water: H2O  H+ + OH- (hydrogen ion and hydroxide ion) water is neutral in pH.
OR H+ + H2O  H3O+ (hydronium ion)
Acid: substances that put H+ into solution
Base: substances that put OH- into solution.
pH: range is 0 to 14.
Near zero is very acidic
Near 14 is very alkaline or basic.
7 is neutral (an equal # of H+ and H3O+ )
Buffers: neutralize small amounts of acid or base