1. Water and the Fitness of the Environment

2. Polarity
Water is composed of oxygen atom covalently bonded to 2 hydrogen atoms.
It is a “polar” molecule because the electrons are unevenly distributed among the atoms.
Water molecules are attracted to each other due to partially positive and partially negative charges
Hydrogen bonds are the basis for water’s unique properties.

3. Cohesion Hydrogen bonding keeps water molecules close together.
Water has greater surface tension (how difficult it is to stretch or break the surface of a liquid) than most other liquids.
Adhesion – clinging of one substance (H2O) to another (cell walls)

5. Expansion upon Freezing
Ice floats on liquid water because its more organized hydrogen bonding causes expansion into a less dense crystal formation.
Protects aquatic life

6. Solutions and Suspensions
Mixture – a material composed of 2 or more elements/compounds that are physically (but not chemically) combined.
2 Kinds:
Solutions – mixtures whose components are evenly distributed
Composed of Solvent (causing dissolving) and Solute (being dissolved)
Suspensions – mixtures with nondissolved materials

7. Acidic and Basic Conditions
Water can dissociate into H+ and OH-
Concentration of H+ is expressed as pH
pH ranges from 0-14
Each step is 10x different
Neutral solution…
[H+] = pH=7
Buffer solution…
Acid-base pairs that resist changes in pH

8. Acidic and Basic Conditions
Acidic Solution
Basic “alkaline” Solution
donate H+ in aqueous solutions
[H+] is greater than [OH-]
pH is less than 7
donate OH- in aqueous solutions
[OH-] is greater than [H+]
pH is greater than 7