Should we control a chemical that:

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

2. What is the chemical? • Dihydrogen monoxide • Otherwise known as H2O

3. Chapter 2Water and the Fitness of the Environment

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

6. States of Matter Liquid Gas Solid

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. – + H – + H + –  – + Figure 3.2 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.

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

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

11. Water transport in trees uses Cohesion and Adhesion

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

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

15. Water Has A High Specific Heat • 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. • Why? Hydrogen bonding. • Heat is absorbed when hydrogen bonds break • Heat is released when hydrogen bonds form

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

17. Celsius Scale • Will be used for most of our temperature measurements. • O oC - water freezes • 100 oC - water boils • 37 oC - 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. • Result - climate moderation • Water stabilizes air temperatures by absorbing heat from the Sun and from air that is warmer and releasing the stored heat to air that is cooler. • Water is effective as a heat bank because it can absorb or release a relatively large amount of heat with only a slight change in its own temperature. This is the reason coastal areas generally have milder climates than inland regions. • Result – stabilized ocean temperatures create a favorable environment for marine life • 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.

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. • Water must absorb a large amount of heat to break its hydrogen bonds from a liquid to a gas. • This helps to moderate Earth’s climate.

21. Evaporative Cooling Evaporative Cooling

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

23. Water Expands When It Freezes • The distance between water molecules INCREASES from the liquid to the solid form. • Why? • 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.

26. Solids and Liquids Water Benzene 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.

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

29. Water Is The Universal Solvent • Water will form a solution with many materials. • Why? 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. Solvent The dissolving agent. The material in the greater quantity. SoluteThe substance that is dissolved. The material in the lesser quantity. SolutionHomogeneous mixture of two or more substances.

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

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

37. Without Water Life Would Not Be Possible!!

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

39. Moles • 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. • Avogadro’s number is the number of molecules in a mole. 6.02 X 1023

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

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

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

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

44. Acid Rain

45. Acid Rain

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

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

48. pH Scale

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