1

2

Hydrogen bonding

3

Surface tension

4

Ice, water, vapor

5

Hydrogen bonding (electric attraction)

Ice Liquid

6

Water-soluble protein

7

“Dissociation” of water

8

pH

pH = – log [H+]

Log scale means 10X change per unit!

[H+]= 10-1M

[H+]= 10-9 M

9

Buffers•Buffers resist changes to the pH of a solution when H+ or OH- is added to the solution.

•Buffers accept hydrogen ions from the solution when they are in excess and donate hydrogen ions when they have been depleted.

10

Overall lessons:

• Many properties of water are emergent properties due to hydrogen bonding.

• The cohesion of water molecules to each other is exploited by plants and animals.

• Water resists temperature changes by absorbing lots of heat.

• Lower density of ice causes it to float & insulate the water below.

• The polarity of water allows it to dissolve other polar molecules.

• Non-polar compounds are hydrophobic and not easily dissolved in water.

• A mole of a compound has a constant # of molecules.

• Adding or removing hydrogen ions changes the pH of a solution.

• Buffers resist pH changes by accepting or donating H ions when [H+] changes.