1. Honors Bio: 2-3 Solutions

2.  Solution : a mixture of two or more substances uniformly mixed together – can be PHYSICALLY separated. (often clear) ◦ Ex: plasma, air, salt water, whipped cream  Solute : the substance dissolved.  Solvent : The dissolving substance; usually the greater amount.  Aqueous Solution : water is the solvent.

3.  The separating of a molecule into simpler molecules or ions.  In water, the force of attraction between water molecules (due to its POLARITY) or between water and other molecules is so strong that it can separate and remove atoms.  In water, this results in the formation of OH - and H + ions (in EQUAL concentrations)

4. A very small percentage of the H 2 O molecules dissociate to form H + and OH – ions. Most of the molecules in pure water remain intact as H 2 O.

5.  An acid is an aqueous solution that contains a greater concentration of H + ions (compared to OH - ions).  Hydronium ions : form when free H + ions react with other water molecules.  pH : measures the concentration of H + ions in a solution.

6.  Acids taste SOUR  pH <7  Litmus RED  Weak acids: ◦ Acetic acid (vinegar-CH 3 COOH) ◦ Carbonic acid (H 2 CO 3 ) ◦ Lactic acid  Strong acids: ◦ Hydrochloric Acid (HCl) ◦ Nitric acid (HNO 3 ) ◦ Sulfuric Acid (H 2 SO 4 )

9. Mostly Weak AcidsBiological Importance  Carbonic Acid (H 2 CO 3 )  Lactic Acid (CH 3 CH(OH)COOH)  Formic Acid (HCOOH)  Hydrochloric acid (strong acid)  Sea water, human blood, soft drinks  Active muscles, milk, microorganisms  Poison in stings from ants & nettle plants.  Stomach acid

10.  An alkaline solution contains more hydroxide (OH - ) than hydrogen (H + ) ions.  Bases taste BITTER  Bases feel SLIPPERY  Ph>7 / Litmus turns BLUE  Ex: soap, baking soda, bleach, ammonia, “draino”

11.  Acid + Base Salt + H 2 O  Ex: HCL + NaOH NaCl + H 2 O  Buffer: chemical substances that neutralize small amounts of acids & bases.  Buffers keep pH constant.  Buffers are composed of a weak acid + conjugate base.

12.  Proteins DENATURE when pH changes  Buffer solutions are necessary to keep the correct pH for enzymes (proteins) in many organisms to work. Curdled Milk