3. The Chemistry of Life Properties of Water

4. Water is the single most abundant substance on Earth!

5. What are the Properties of Water?

6. Water is different than other substances – it expands as it freezes!

7. Properties of Water At sea level, pure water boils at 100 °C and freezes at 0 °C.At sea level, pure water boils at 100 °C and freezes at 0 °C. The boiling temperature of water decreases at higher elevations (lower atmospheric pressure).The boiling temperature of water decreases at higher elevations (lower atmospheric pressure). For this reason, an egg will take longer to boil at higher altitudesFor this reason, an egg will take longer to boil at higher altitudes

8. Water threeA water molecule (H 2 O), is made up of three atoms --- one oxygen and two hydrogen. H H O Nicknamed “Mickey Mouse Molecule”

9. The Water Molecule Neutral Charge –All Molecules of Water are Neutral –Equal number of e - and p +

10. Water Water is polar!

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

12. Water is Polar oxygen atom attracts more electronsIn each water molecule, the oxygen atom attracts more than its "fair share" of electrons oxygennegativeThe oxygen end “acts” negative hydrogenpositiveThe hydrogen end “acts” positive POLARCauses the water to be POLAR neutral Zero Net ChargeRemember, Water is neutral (equal number of e- and p+) --- Zero Net Charge

13. 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 –One hydrogen bond is weak, but many hydrogen bonds are strong

14. Hydrogen Bonds Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule to form a HYDROGEN BONDNegative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule to form a HYDROGEN BOND

15. Water is cohesive!

16. Cohesion The attraction between molecules of the same substance (e.g. 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) Produces a surface film on water that allows many drops of water to be on top of one penny and insects to walk on the surface of waterProduces a surface film on water that allows many drops of water to be on top of one penny and insects to walk on the surface of water

17. Cohesion … Helps insects walk across water

18. Cohesion … How many drops did you get on your penny?

19. Adhesion Attraction between molecules of different substancesAttraction between molecules of different substances Adhesion between water and plants is Responsible for Capillary forces in plantsAdhesion between water and plants is Responsible for Capillary forces in plants

20. Capillary Action Capillary action-water molecules will “tow” each other along when in a thin glass tube.Capillary action-water molecules will “tow” each other along when in a thin glass tube. Example: transpiration process which plants and trees remove water from the soil, and paper towels soak up water.Example: transpiration process which plants and trees remove water from the soil, and paper towels soak up water.

21. Adhesion Also Causes Water to … Form spheres & hold onto plant leaves Attach to a silken spider web

22. Adhesion Causes Capillary Action Which gives water the ability to “climb” structures Try it!

23. High Specific Heat Amount of heat needed to raise or lower 1g of a substance 1° C. 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.

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

25. Water vaporWater vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm. Heat radiated from the sunHeat radiated from the sun warmed surface of the earth is absorbed and held by the vapor by the vapor.

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

27. Water is Less Dense as a Solid Which is ice and which is water?Which is ice and which is water?

28. Water is Less Dense as a Solid WaterIce

29. 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 (insulates frozen lakes)

30. Solutions & Suspensions Water is usually part of a mixture.Water is usually part of a mixture. There are two types of mixtures:There are two types of mixtures: –Solutions –Suspensions

31. 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

32. Solution

33. 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.

34. 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 -

35. The pH Scale Indicates the concentration of H + ions Ranges from 0 – 14 pH of 7 is neutral pH 0 – 6.99 is acid … H + pH 7.01 – 14 is basic… OH - Each pH unit represents a factor of 10 change in concentration

36. Acids and Bases pH Scale indicates the concentration of H + ions Ranges from 0 – 14 pH of 7 is neutral pH 0 – 6.99 is acid … H + pH 7.01 – 14 is basic… OH - Each pH unit represents a factor of 10 change in concentration

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

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

39. Buffers Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH.Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH. Weak Acid Weak Base

40. Acid Rain Rain, snow or fog with more strongly acidic than pH of 5.6 West Virginia has recorded 1.5 East Tennessee reported 4.2 in 2000 Occurs when sulfur oxides and nitrogen oxides react with water in the atmosphere –Lowers pH of soil which affects mineral solubility – decline of forests –Lower pH of lakes and ponds – In the Western Adirondack Mountains, there are lakes with a pH <5 that have no fish.

41. Now – Summarize your notes! Quiz next time!