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Chapter 3: Water and Life

Chapter 3: Water and Life

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Chapter 3: Water and Life

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  1. Chapter 3: Water and Life

  2. Essential Knowledge 2.a.3 – Organisms must exchange matter with the environment to grow, reproduce, and maintain organization (3.1-3.3).

  3. 7 Properties of Water 1) Cohesive 2) Adhesive 3) High surface tension 4) Stabilizes temperatures 5) High heat of vaporization 6) Expands when frozen 7) Versatile solvent

  4. 1) Liquid Water Is Cohesive • Water sticks to water. • Why? • Because the polarity of water results in hydrogen bonding. • Contributes to transport of nutrients (plants)

  5. 2) Liquid Water is Adhesive • Water sticks to other molecules. • Why? • Hydrogen bonding. • Plants: • Water adheres to cell walls (helps pull water and nutrients through plant)

  6. Water transport in trees uses Cohesion and Adhesion

  7. 3) Water Has A High Surface Tension • The surface of water is difficult to stretch or break. • Why? Hydrogen bonding. • Greater surf tension than most liquids

  8. 4) Water Stabilizes Temperature • Water can absorb and store a huge amount of heat from the sun. • Result - climate moderation • Result - organisms are able to survive temperature changes.

  9. 5) 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. • Results: • Water cools organisms from excessive heat buildup. • Why? • Hydrogen bonding

  10. 6) Water Expands When It Freezes • The distance between water molecules INCREASES from the liquid to the solid form. • Result: • Aquatic life can live under ice. • Why? • Hydrogen bonding

  11. Solids and Liquids Water Benzene Floats Sinks

  12. States of Matter Solid Liquid Gas

  13. 7) Water Is A Versatile Solvent • Water will form a solution with many materials. • Considered the best solvent • Why? • Hydrogen bonding

  14. Solvent • The dissolving agent. • The material in the greater quantity. • Ex: • Water • Alcohols • Buffers • Water is the best solvent • Why? Versatile (can dissolve MOST solutes)

  15. Solute • The substance that is dissolved. • The material in the lesser quantity. • Ex: • Salt • Sugar • Kool-aid powder

  16. 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.

  17. Hydrophobic • Materials that repel water. • Hydro - water • phobic - to fear • Have non-polar covalent bonds. • Remember: In npc bonds, e- are shared evenly. • Ex: • Lipids • Cell membrane components

  18. Quick Review • What is cohesion? • What is adhesion? • Name the main reason that water possesses the properties that it does. • Give an example of each of the following: • Solute • Solvent

  19. SolutionConcentration • Usually based on Molarity. • Molarity - the number of moles of solute per liter of solution. • Use mass to calculate # of molecules

  20. Moles • The molecular weight of a substance in grams. • One Avogadro’s number of molecules. • 6.02 X 1023 = 1 mole

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

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

  23. Dissociation of Water, Continued Adding certain solutes disrupts the balance between the two ions. The two ions are very reactive and can drastically affect a cell.

  24. Acids • Materials that can release H+ (when dissolved in water) • pH = 0-7 (6.9) • Example: HCl HCl H+ + Cl-

  25. Bases • Materials that can absorb H+ • Often reduce H+ (by producing OH- ) • pH = 7.1-14 • Example: NaOH, blood (7.4-7.8), bleach

  26. Neutrals • Materials that are neither acids nor bases. • pH = 7 (ish) • Usually 6.5-7.4 • Ex: • Urine

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

  28. pH Scale

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

  30. pH, cont. • Acids: pH <7 etc. • Bases: pH >7 etc. • Each pH unit is a 10x change in H+ • [H+] + [OH-] = 14 • Therefore, if you know the concentration of one ion, you can easily calculate the other.

  31. Buffers • Materials that have both acid and base properties. • Resist pH shifts. • Cells and other biological solutions often contain buffers

  32. Buffers, cont. • Advantage: • Prevents damage to cell/DNA • pH changes can denature proteins • Ex: • Buffers in blood keep pH around a slightly basic pH • Most are acid-base pairs

  33. Summary • Recognize the chemical structure of water. • Relate the structure of water to its properties. • Identify and discuss the unique properties of water. • Calculate specific concentrations of solutions (moles). • Recognize pH and the pH scale. • Recognize acids, bases, and buffers.