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Ch. 3 Warm-Up

Delve into the crucial properties of water that support life on Earth, such as cohesion, adhesion, and temperature moderation. Learn about its role as a versatile solvent and how hydrogen bonding shapes its functions. Explore the pH scale, buffers in biological systems, and emergent properties like expansive freezing. Discover the significance of water in ecosystems and human biology.

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Ch. 3 Warm-Up

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  1. Ch. 3 Warm-Up What property of water allows a water strider to “walk” on water? Contrast adhesion and cohesion. Give an example of each. Contrast hydrophobic and hydrophilic substances. Give an example of each.

  2. Chapter 3 Water and the Fitness of the Environment

  3. You Must Know • The importance of hydrogen bonding to the properties of water. • Four unique properties of water, and how each contributes to life on Earth. • How to interpret the pH scale. • The importance of buffers in biological systems.

  4. 4 Emergent Properties of Water • Cohesive behavior • Ability to moderate temperature • Expansion upon freezing • Versatility as a solvent

  5. 1. Polarity of H2O • O- will bond with H+ on a different molecule of H2O = hydrogen bond • H2O can form up to 4 bonds

  6. 2. Properties of H2O • Cohesion = H-bonding between like molecules • Surface Tension = measure of how difficult it is to break or stretch surface of liquid

  7. 2. Properties of H2O • Adhesion = bonding between unlike molecules • Adhesion of H2O to vessel walls counters ↓ pull of gravity

  8. 2. Properties of H2O C. Transpiration= movement of H2O up plants • H2O clings to each other by cohesion; cling to xylem tubes by adhesion

  9. 3. Moderation of temperature Heat = Total amount of KE in system Temperature = measure intensity of heat due to average KE of molecules

  10. 3. Moderation of temperature • Water’s high specific heat • Change temp less when absorbs/loses heat • Large bodies of water absorb and store more heat  warmer coastal areas • Create stable marine/land environment • Humans ~65% H2O  stable temp, resist temp. change

  11. 3. Moderation of temperature • Evaporative Cooling • Water has high heat of vaporization • Molecules with greatest KE leave as gas • Stable temp in lakes & ponds • Cool plants • Human sweat

  12. 3. Moderation of temperature • Insulation by ice– less dense, floating ice insulates liquid H2O below • Life exists under frozen surface (ponds, lakes, oceans) • Ice = solid habitat (polar bears)

  13. Hydrogen bond Liquid water:Hydrogen bondsbreak and re-form Ice:Hydrogen bondsare stable

  14. 4. Solvent of life • Solution = liquid, homogeneous mixture of 2+ substances • Solvent = dissolving agent (liquid) • Solute = dissolved substance • Water = versatile/universal solvent

  15. 4. Solvent of life • “like dissolves like”

  16. Figure 3.8 A water-soluble protein

  17. 5. Acids and Bases H2O H+ + OH- (gains proton) H+ + H2O  H3O+ (hydronium ion) (loses proton) H2O – H+  OH-(hydroxide ion)

  18. 5. Acids and Bases Acidic Basic 7 14 0 pH Scale • Acid= increases H+ concentration (HCl) • Base= reduces H+ concentration (NaOH) • Most biological fluids are pH 6-8

  19. Figure 3.10 The pH scale and pH values of some aqueous solutions

  20. Calculating pH [H+][OH-] = 10-14 • If [H+] = 10-6 M, then [OH-] = 10-8 pH = -log [H+] • If [H+] = 10-2 • -log 10-2 = -(-2) = 2 • Therefore, pH = 2 • If [OH-] = 10-10 • [H+] = 10-4 • -log 10-4 = -(-4) = 4 • Therefore, pH = 4

  21. 5. Acids and Bases Buffers: minimize changes in concentration of H+ and OH- in a solution (weak acids and bases) • Buffers keep blood at pH ~7.4 • If blood drops to 7 or up to 7.8, then death Carbonic Acid – Bicarbonate System: important buffers in blood plasma H2CO3 (carbonic acid)  HCO3- (bicarbonate) + H+

  22. Ocean acidification threatens coral reef ecosystems CO2 mixed with seawater  Carbonic acid (lowers ocean pH)

  23. The effects of acid precipitation on a forest

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