Chemistry of WaterChapters 8 + 15 + 16

What Makes Water So Special?

Polarity- water’s bent shape creates δ- and δ+ areas in the molecule

Intermolecular Forces forces of attraction that

occur between molecules of a substance

Hydrogen Bonds Van Der Walls Forces

Dipole-Dipole Interactions

Dispersion Forces

Intermolecular Forces1. Hydrogen Bonding- strongest intermolecular force,

2. 5% of covalent bond.

3. hydrogen is bonded to a strongly electronegative atom (O, N, F) and is also attracted to lone electron pairs on a neighboring molecule

Intermolecular Forces Dipole interactions- van der Waals

forces seen in polar molecules as a result of partial charge distribution

Intermolecular Forces dispersion forces- weakest van der

Waals force caused by motion of electrons and increase as # of electrons increases

Properties of Water Surface Tension- water

has an unusually high surface tension because its molecules are strongly attracted to one another (as opposed to their attraction to air molecules)

Properties of Water Heat Capacity- we are able to inhabit

this planet because it takes a lot of energy to raise the temperature of water

Properties of Water Density of Ice-

decreases from 4 to 0°C because molecules become “locked” in place as kinetic energy is decreased

Water as a Solvent Ionic and Polar Compounds- tend to

become solvated in water to form aqueous solutions…

why?

(Note: some ionic compounds are too strongly attracted to be soluble in water)

Electrolytes all ionic compounds and some highly polar covalent

compounds that can complete an electrical circuit

Types of Electrolytes Strong Electrolytes- inorganic acids, inorganic

bases, and ionic compounds that are completely soluble

Weak Electrolytes- organic acids, organic bases, ionic compounds that are slightly soluble, and highly polar molecules

Nonelectrolytes- nonpolar and organic compounds

Remember? Solutions,

Suspensions, and Colloids...

Properties of Solutions

rate of dissolving is determined by: agitation, temperature, and particle size

Solutions may be unsaturated, saturated, or supersaturated

“like dissolves like”