Biochemistry Continued

Life could not exist without water. Some functions of water include:

Control of body temperature Keeps eyeballs moist Lubricates joints Absorbs shock Protects brain and spinal cord from bruising

Water can exist as a solid, liquid, or gas. Its chemical structure is composed of 2

hydrogen atoms and 1 oxygen atom. Because there is partial sharing of

electrons between the 3 atoms, and because its molecular structure is asymmetrical, water is a polar covalent molecule.

Due to its polarity, water is able to form bonds with other molecules.

These bonds between molecules are called intermolecular bonds.

These bonds are broken when solids melt into liquids, and liquids evaporate into gases.

Water dissolves more substances than any other liquid.

Because of its polarity, water attracts other polar substances (including itself), and dissolves other polar substances.

Any substance that dissolves in water is called a solute.

Water, then, is a solvent.

Often, the subscript “(aq)” is visible. This subscript means that aqueous

substances are soluble in water. A polar molecule that can bond with water

is called a hydrophilic molecule. A nonpolar molecule that cannot bond with

water is called a hydrophobic molecule. Remember : “Like dissolves like”. (i.e., polar

substances dissolve polar substances).

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Worksheet…

When 2 water molecules interact, one molecule gains a hydrogen (to become H3O+, hydronium ion) while the other loses a hydrogen (and becomes OH-, hydroxide ion).

This process is called the autoionization of water.

Acids are defined as substances that increase the concentration of H+ (or H3O+) ions in solution.

Bases are defined as substances that increase the concentration of OH- ions in solution.

When an acid is mixed with a base, the result is a neutralization reaction.

Neutralization reactions produce water and a salt.

A solution with a pH of 7 is considered neutral (equal amounts of H3O+ and OH-).

Solutions whose pH is less than 7 are acidic (more H3O+).

Solutions whose pH is greater than 7 are basic (more OH-).