Properties of Water

Hydrogen bonding

Surface tension

Ice, water, vapor

Hydrogen bonding (electric attraction) Ice Liquid

Water-soluble protein

“Dissociation” of water

pH [H+]= 10-1M pH = – log [H+] Log scale means 10X change per unit!

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.

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.