1. Should we control a chemical that: Causes excessive sweating and vomiting. Causes excessive sweating and vomiting. Is a major component in acid rain. Is a major component in acid rain. Can cause severe burns in its gaseous state. Can cause severe burns in its gaseous state. Accidental inhalation can kill you. Accidental inhalation can kill you. Contributes to erosion. Contributes to erosion. Decreases the effectiveness of car brakes. Decreases the effectiveness of car brakes. Has been found in tumors of terminal cancer patients. Has been found in tumors of terminal cancer patients.

2. What is the chemical? Dihydrogen monoxide Dihydrogen monoxide Otherwise known as H 2 O Otherwise known as H 2 O

3. Chapter 2 Water and the Fitness of the Environment

4. Three-quarters of the Earth’s surface is submerged in water Three-quarters of the Earth’s surface is submerged in water The abundance of water is the main reason the Earth is habitable The abundance of water is the main reason the Earth is habitable Water is the biological medium here on Earth Water is the biological medium here on Earth All living organisms require water more than any other substance All living organisms require water more than any other substance Most cells are composed of 70-95% water. Most cells are composed of 70-95% water. Figure 3.1

6. Solid LiquidGas States of Matter

7. Water is a polar molecule (oxygen is more electronegative than hydrogen creating a partial negative charge on oxygen and a partial positive charge on hydrogen)

8. The polarity of water molecules results in unique properties. Each water molecule can form 4 hydrogen bonds. The extraordinary qualities of water are emergent properties resulting from the hydrogen bonding. + + H H + +  – –  – –  – –  – – Figure 3.2

9. Liquid Water Is Cohesive Water sticks to water. Water sticks to water. Why? Why? Because the polarity of water results in hydrogen bonding. Because the polarity of water results in hydrogen bonding.

10. Liquid Water is Adhesive Water sticks to other molecules. Water sticks to other molecules. Why? Why? Hydrogen bonding. Hydrogen bonding.

11. Water transport in trees uses Cohesion and Adhesion

13. Cohesion Cohesion Helps pull water up through the microscopic vessels of plants Helps pull water up through the microscopic vessels of plants Water conducting cells 100 µ m Figure 3.3

14. Water Has A High Surface Tension The surface of water is difficult to stretch or break. The surface of water is difficult to stretch or break. Why? Hydrogen bonding. Why? Hydrogen bonding. Figure 3.4

15. Water Has A High Specific Heat Specific Heat - the amount of heat needed to raise 1 g of the substance 1 degree C. Specific Heat - the amount of heat needed to raise 1 g of the substance 1 degree C. A measure of how well a substance resists changing its temperature when it absorbs or releases heat. A measure of how well a substance resists changing its temperature when it absorbs or releases heat. Why? Why? Hydrogen bonding. Hydrogen bonding. Heat is absorbed when hydrogen bonds break Heat is absorbed when hydrogen bonds break Heat is released when hydrogen bonds form Heat is released when hydrogen bonds form

16. Temperature Measures the average speed of the molecules. Measures the average speed of the molecules. Heat Total quantity of kinetic energy due to Total quantity of kinetic energy due to molecular motion. molecular motion.

17. Celsius Scale Will be used for most of our temperature measurements. Will be used for most of our temperature measurements. O o C - water freezes O o C - water freezes 100 o C - water boils 100 o C - water boils 37 o C - human body 37 o C - human body

19. Water Stabilizes Temperature Because of its high specific heat, water can absorb and store a huge amount of heat from the sun. Because of its high specific heat, water can absorb and store a huge amount of heat from the sun. Result - climate moderation Result - climate moderation Water stabilizes air temperatures by absorbing Water stabilizes air temperatures by absorbing heat from the Sun and from air that is warmer and heat from the Sun and from air that is warmer and releasing the stored heat to air that is cooler. releasing the stored heat to air that is cooler. Water is effective as a heat bank because it can absorb or Water is effective as a heat bank because it can absorb or release a relatively large amount of heat with only a slight release a relatively large amount of heat with only a slight change in its own temperature. This is the reason coastal change in its own temperature. This is the reason coastal areas generally have milder climates than inland regions. areas generally have milder climates than inland regions. Result – stabilized ocean temperatures create a favorable environment for marine life Result – stabilized ocean temperatures create a favorable environment for marine life Result - organisms are able to survive temperature changes. Result - organisms are able to survive temperature changes. Because organisms are made primarily of water, they are able to resist changes in their own temperatures. able to resist changes in their own temperatures.

20. Water Has A High Heat Of Vaporization Heat of Vaporization: the quantity of heat a liquid must absorb for 1g of it to convert to a gaseous state. Heat of Vaporization: the quantity of heat a liquid must absorb for 1g of it to convert to a gaseous state. Water must absorb a large amount of heat to break its hydrogen bonds from a liquid to a gas. Water must absorb a large amount of heat to break its hydrogen bonds from a liquid to a gas. This helps to moderate This helps to moderate Earth’s climate. Earth’s climate.

21. Evaporative Cooling

22. Result: As a liquid evaporates, the surface of the liquid that remains behind cools down. As a liquid evaporates, the surface of the liquid that remains behind cools down. Contributes to the stability of temperature in lakes and ponds Contributes to the stability of temperature in lakes and ponds Provides a mechanism that prevents terrestrial organisms from overheating EX. sweating Provides a mechanism that prevents terrestrial organisms from overheating EX. sweating Why? Why? Hydrogen bonding Hydrogen bonding

23. Water Expands When It Freezes The distance between water molecules INCREASES from the liquid to the solid form. The distance between water molecules INCREASES from the liquid to the solid form. Why? Why? Hydrogen bonding Hydrogen bonding Hydrogen bonds keep the water molecules far enough apart that they lock into a crystalline lattice structure, making ice about 10% less dense than water at 4 degrees Celsius. Hydrogen bonds keep the water molecules far enough apart that they lock into a crystalline lattice structure, making ice about 10% less dense than water at 4 degrees Celsius.

26. Solids and Liquids WaterBenzene Floats Sinks

27. Result Floating ice insulates the liquid water below, preventing it from freezing and allowing aquatic life to live under the frozen surface. Floating ice insulates the liquid water below, preventing it from freezing and allowing aquatic life to live under the frozen surface.

28. Liquid water Hydrogen bonds constantly break and re-form Ice Hydrogen bonds are stable Hydrogen bond Figure 3.5

29. Water Is The Universal Solvent Water will form a solution with many materials. Water will form a solution with many materials. Why? Why? Hydrogen bonding Hydrogen bonding Water is polar (unequal sharing of electrons) ionic substances are soluble in water polar dissolves polar ( sugar in water) Nonpolar substances do not dissolve in water EX. lipids

30. Solution Homogeneous mixture of two or more substances. Solvent The dissolving agent. The material in the greater quantity. Solute The substance that is dissolved. The material in the lesser quantity.

33. Hydrophilic Materials Materials that dissolve in water. Materials that dissolve in water. Hydro - water Hydro - water philic - to like or love philic - to like or love Have ionic or polar regions (polar covalent bonds) on their molecules for H + bonds. Have ionic or polar regions (polar covalent bonds) on their molecules for H + bonds.

36. Hydrophobic Materials that repel water. Materials that repel water. Hydro - water Hydro - water phobic - to fear phobic - to fear Have non-polar covalent bonds. Ex - lipids. Have non-polar covalent bonds. Ex - lipids.

37. Without Water Life Would Not Be Possible!!

38. Solution Concentration Usually based on Molarity. Usually based on Molarity. Molarity - the number of moles of solute per liter of solution. Molarity - the number of moles of solute per liter of solution.

39. Moles The molecular weight of a substance in grams. The molecular weight of a substance in grams. A mole of one substance has exactly the same number of molecules as a mole of another substance. A mole of one substance has exactly the same number of molecules as a mole of another substance. Avogadro’s number is the number of molecules in a mole. Avogadro’s number is the number of molecules in a mole. 6.02 X 10 23 6.02 X 10 23

40. One Mole of each Sulfur Sugar Copper Sulfate Mercury Oxide Copper Sodium Chloride

41. Dissociation of Water Water can sometimes split into two ions. Water can sometimes split into two ions. In pure water the concentration of each ion is 10 -7 In pure water the concentration of each ion is 10 -7

42. Adding certain solutes disrupts the balance between the two ions. Adding certain solutes disrupts the balance between the two ions. The two ions are very reactive and can drastically affect a cell. The two ions are very reactive and can drastically affect a cell.

43. Acids Materials that can release H + Materials that can release H + increases the hydrogen ion concentration of a solution increases the hydrogen ion concentration of a solution Example: HCl Example: HCl HCl H + + Cl - HCl H + + Cl -

44. Acid Rain

46. Bases Materials that can absorb H + Materials that can absorb H + Often reduce H + by producing OH - Often reduce H + by producing OH - Example: NaOH Example: NaOH NaOH Na + + OH - NaOH Na + + OH -

47. pH Scale A logarithmic scale for showing H + concentration A logarithmic scale for showing H + concentration pH = - log [H + ] pH = - log [H + ]

48. pH Scale

50. Example: For a neutral solution: [H + ] is 10 -7 or - log 10 -7 or - (-7) or 7

51. Acids: pH <7 etc. Acids: pH <7 etc. Bases: pH >7 etc. Bases: pH >7 etc. Each pH unit is a 10x change in H + Each pH unit is a 10x change in H +

52. Comment [H + ] + [OH - ] = 14 [H + ] + [OH - ] = 14 Therefore, if you know the concentration of one ion, you can easily calculate the other. Therefore, if you know the concentration of one ion, you can easily calculate the other.

53. Buffers The internal pH of most living cells The internal pH of most living cells Must remain close to pH 7 Must remain close to pH 7

54. Buffers Materials that have both acid and base properties. Materials that have both acid and base properties. Resist pH shifts. Resist pH shifts. Cells and other biological solutions often contain buffers to prevent damage. Cells and other biological solutions often contain buffers to prevent damage.

55. Buffers Buffers Are substances that minimize changes in the concentrations of hydrogen and hydroxide ions in a solution Are substances that minimize changes in the concentrations of hydrogen and hydroxide ions in a solution Consist of an acid-base pair that reversibly combines with hydrogen ions Consist of an acid-base pair that reversibly combines with hydrogen ions

56. The Threat of Acid Precipitation Acid precipitation Acid precipitation Refers to rain, snow, or fog with a pH lower than pH 5.6 Refers to rain, snow, or fog with a pH lower than pH 5.6 Is caused primarily by the mixing of different pollutants with water in the air Is caused primarily by the mixing of different pollutants with water in the air Caused primarily by the presence in the atmosphere of sulfur oxides and nitrogen oxides, created by the burning of fossil fuels Caused primarily by the presence in the atmosphere of sulfur oxides and nitrogen oxides, created by the burning of fossil fuels

57. Acid precipitation Acid precipitation Can damage life in Earth’s ecosystems Can damage life in Earth’s ecosystems 0101 2323 4545 6767 8989 10 11 12 13 14 More acidic Acid rain Normal rain More basic Figure 3.9