Terms to know: Matter, Element, Compound, Atomic Number, Atomic Mass (Mass Number), Ion, Isotope, Valence electrons, Ionic Bond, Covalent Bond (single, double, polar, non-polar).

A solvent is a substance that dissolves something else. The substance dissolved is the solute, e.g. table salt is a solute when it is dissolved in water.

Water molecules contain polar covalent bonds because the oxygen atom is more electronegative than the hydrogen atoms and this results in an uneven ‘pull’ on the shared electrons. Water is therefore a ‘polar’ molecule and has the ability to form hydrogen bonds. Hydrogen bonds form between neighboring water molecules; it is a relatively weak attraction between the partially negative portion of one water molecule and the partially positive portion of the adjacent molecule. Hydrogen bonds are critical to the unique nature of water.

Other polar molecules will dissolve easily in water because the charged poles of the solute are attracted to oppositely charged regions of water. These polar or charged molecules are hydrophilic, (‘water-loving’) because of their attraction for water.

Non-polar molecules (which have evenly distributed charge) do not dissolve easily in water and are called hydrophobic (‘water-fearing’). However, water still has an effect on those molecules. And once again, it’s due to water’s hydrogen bonds.

Gasoline, oil, etc. Any water molecule adjacent to a hydrophobic molecule cannot hydrogen bond with it, creating an effect where all the hydrophobic molecules are ‘pushed’ together to minimize the hydrogen bond disruption. Also, since gasoline and oil are less dense than water, they float on top of the water, which also minimizes the hydrogen bond disruption.

H-O-H ß à OH- and H+ (hydroxide ion and hydrogen ion)

Acids higher concentration of H+

Bases higher concentration of OH-

pH scale (measures potential hydrogen) between each pH unit there is a 10-fold increase in the number of H+ ions.

Buffers

Bicarbonate

Phosphate

When cells become too acidic:

When cells become too basic:

Effects of acid environment on an ecosystem

Chemical Reactions - only rearrange atoms in various ways

Reactants on left of arrow

Products on right of arrow