1. The Chemistry of Life Properties of Water

2. Water A water molecule (H 2 O), is made up of three atoms: one oxygen and two hydrogen. H H O

3. Properties of Water What are they?What are they?

4. Properties of Water Polar MoleculePolar Molecule CohesionCohesion AdhesionAdhesion High Specific HeatHigh Specific Heat High Heat of VaporizationHigh Heat of Vaporization Less Dense as a SolidLess Dense as a Solid

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

6. 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 the strongest bonds that can form between molecules

7. Hydrogen Bonds

8. Cohesion The attraction between molecules of the same substance (e.g. water). Allows some insects and spiders to walk on water. Results in: Surface tension (a measure of the strength of water’s surface)Results in: Surface tension (a measure of the strength of water’s surface)

9. Adhesion Attraction between molecules of different substances (makes water stick to other substances)Attraction between molecules of different substances (makes water stick to other substances) Responsible for Capillary forces in plantsResponsible for Capillary forces in plants Capillary action-water molecules will “tow” each other along when in a thin glass tube. (or another surface, happens in plants as well)Capillary action-water molecules will “tow” each other along when in a thin glass tube. (or another surface, happens in plants as well)

10. High Specific Heat Amount of heat needed to raise or lower 1g of a substance 1° C. Water resists temperature change, both for heating and cooling.Water resists temperature change, both for heating and cooling. Water can absorb or release large amounts of heat energy with little change in actual temperature.Water can absorb or release large amounts of heat energy with little change in actual temperature.

11. High Heat of Vaporization Amount of energy to convert 1g or a substance from a liquid to a gas In order for water to evaporate, hydrogen bonds must be broken. As water evaporates, it removes a lot of heat with it. In order for water to evaporate, hydrogen bonds must be broken. As water evaporates, it removes a lot of heat with it.

12. “ Water vapor forms a kind of global‘blanket’ which helps to keep the earth warm. Heat radiated from the sun-warmed surface of the earth is absorbed and held by the vapor.”

13. Water is Less Dense as a Solid Ice is less dense as a solid than as a liquid (ice floats) Liquid water has hydrogen bonds that are constantly being broken and reformed. Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances.

14. Homeostasis Ability to maintain a steady state despite changing conditionsAbility to maintain a steady state despite changing conditions Water is important to this process because:Water is important to this process because: a. Makes a good insulator b. Resists temperature change c. Universal solvent d. Coolant e. Ice protects against temperature extremes

15. Solutions & Suspensions Water is usually part of a mixture.Water is usually part of a mixture.

16. Solution Ionic compounds disperse as ions in waterIonic compounds disperse as ions in water Evenly distributedEvenly distributed SOLUTESOLUTE –Substance that is being dissolved SOLVENTSOLVENT –Substance into which the solute dissolves

17. Solution

18. 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 -

19. The pH Scale Measure of the concentration of H + ions Ranges from 0 – 14 pH of 7 is neutral (water) pH 0 – 6.99 is acid … H + pH 7.01 – 14 is basic… OH -

20. Acids Strong Acid = pH 1-3 H + ions

21. Bases Strong Base = pH 11 – 14 OH - ions

22. Buffers Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH. Will neutralize the substanceWeak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH. Will neutralize the substance Weak Acid Weak Base