Acids, Bases and Buffers CHEMISTRY of WATER Acids, Bases and Buffers

Structure and geometry of water

Four hydrogen bonds

PROPERTIES OF WATER Cohesion and adhesion High heat specificity High heat of vaporization Expands as freezes (less dense as solid) Universal solvent

Adhesion and Cohesion Adhesion – H bonds on water molecules attract to surfaces of another substance ex – the sides of a vessel (xylem/phloem), causes meniscus shape in grad. cyclinders

Transpiration in plants

Water has a high specific heat

Why important to life? This property allows for life b/c 1. External environments are controlled in part b/c of this property. Ex. Large bodies of water stabilize air temperature due to HIGH SPECIFIC HEAT of water. 2. Internal environments of living organisms are controlled by this property. High Specific heat of water keeps internal temp. flucuations to a minimum.

High Heat of Vaporization

Why important? Globally – this acts as a cooling device and maintains global climates (think Gulf Stream)

Protects terrestrial organisms from overheating – as liquid vaporizes, the water left behind actually loses the kinetic energy of the escaped molecules causing the remaining liquid to cool down

Expands as freezes

Why important? Floating ice actually insolates the liquid water below allowing for life. Oceans and lakes don’t freeze solid due to this property

Universal Solvent

Solutes that dissolve in water Hydrophilic – water loving substances ions, salts, polar molecules Hydrophobic – water fearing oils, hydrocarbon chains, Nonpolar molecules

Link http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/watercon.html#c1

Dissociation of Water

pH Scale

Buffers

Bicarbonate Buffer System

AP EXAM ESSAY 1.  The unique properties (characteristics) of water make life possible on Earth. Select three properties of water and: for each property, identify and define the property and explain it in terms of the physical/chemical nature of water. for each property, describe one example of how the property affects the functioning of living organisms.