Page 1 The Chemistry of Life Properties of Water

Page 2 The Water Molecule Neutral Charge – ZERONeutral Charge – ZERO Have no charge Have an Equal number of p+ and e- Charges aren’t evenly distributed

Page 3 The Water Molecule PolarityPolarity uneven distribution of electrons –A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms. (-) (+) (+)

Page 4 Hydrogen Bonds Polar water molecules act like magnets and attract each otherPolar water molecules act like magnets and attract each other Hydrogen BondsHydrogen Bonds –The attraction of the Hydrogen end (+) of one molecule for the Oxygen end (-) of another water molecule. They are strong bonds that form between molecules (CO 2, H 2 O, …)They are strong bonds that form between molecules (CO 2, H 2 O, …)

Page 5 Hydrogen Bonds

Page 6 Cohesion The attraction between molecules of the same substance (e.g. water). H 2 O attracting other H 2 O moleculesH 2 O attracting other H 2 O molecules Allows some insects and spiders to walk on water.

Page 7 Adhesion & Capillarity Adhesion - Attraction between H 2 O molecules and different moleculesAdhesion - Attraction between H 2 O molecules and different molecules Cohesion & adhesion produce Capillarity (upward movement against gravity of water through small tubes)Cohesion & adhesion produce Capillarity (upward movement against gravity of water through small tubes) Question: How do plants make use of Capillarity?

Page 8 Solutions & Suspensions Water is usually part of a mixture.Water is usually part of a mixture. Because so many things dissolve in water, it is called the Universal SolventBecause so many things dissolve in water, it is called the Universal Solvent There are two types of mixtures:There are two types of mixtures: –Solutions –Suspensions

Page 9 Properties of Solutions Ionic compounds disperse as ions in water (+ions & -ions spread out among polar water molecules)Ionic compounds disperse as ions in water (+ions & -ions spread out among polar water molecules) Solutions are Evenly distributed mixturesSolutions are Evenly distributed mixtures SOLUTESOLUTE –Substance that is being dissolved SOLVENTSOLVENT –Dissolving Substance for the solute

Page 10 Ionic Solutions Na+ ions will be attracted to WHAT END of the water molecule?

Page 11 Suspensions Substances that don’t dissolve but separate into tiny pieces.Substances that don’t dissolve but separate into tiny pieces. Water keeps the pieces suspended so they don’t settle out.Water keeps the pieces suspended so they don’t settle out. Blood & Cytoplasm are suspensionsBlood & Cytoplasm are suspensions

Page 12 Acids, Bases & pH 1 water molecule in 550 million naturally dissociates into a Hydrogen Ion and a Hydroxide Ion1 water molecule in 550 million naturally dissociates into a Hydrogen Ion and a Hydroxide Ion Hydrogen Ion Hydroxide Ion Acid Base Acid Base H 2 O  H + + OH -

Page 13 The pH Scale Indicates the concentration of H + ions Ranges from 0 – 14 pH of 7 is neutral pH 0 up to 7  acid … H + pH above 7 to 14  base… OH - Each pH unit represents a factor of 10X change in concentration How much stronger is a pH3 than a pH of 5?

Page 14 Acids Strong Acid = pH 1-3 High in H + ions Lower number of OH- ions

Page 15 Bases Strong Base = pH 11 – 14 High in OH - ions Lower in number of H+ ions

Page 16 Buffers Weak acids or bases that react with strong acids or basesWeak acids or bases that react with strong acids or bases Made by the bodyMade by the body Prevent sharp, sudden changes in pH (keep pH neutral)Prevent sharp, sudden changes in pH (keep pH neutral) Weak Acid Weak Base