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Water & Life

Water & Life. Chapter 3. H2O is why we are here. H 2 O molecules are polar What does their polarity contribute to? Each H 2 O molecule can form __ Hydrogen bonds?. Cohesion & Adhesion. Caused by Hydrogen bonding Cohesion – Water-to-water Adhesion – Water-to-something other than water

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Water & Life

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  1. Water & Life Chapter 3

  2. H2O is why we are here • H2O molecules are polar • What does their polarity contribute to? • Each H2O molecule can form __ Hydrogen bonds?

  3. Cohesion & Adhesion • Caused by Hydrogen bonding • Cohesion – Water-to-water • Adhesion – Water-to-something other than water • When water travels upward in a straw, is that cohesion or adhesion? Why? • Diameter of straw: small or large? Why?

  4. Transpiration (Plants)

  5. Structure & Function in Water Transport • What structural feature of water enables it to be transported upward? • What structural feature of plant vessels enables water to be transported upward?

  6. Properties of Water • 1. High Surface Tension • 2. Temperature Moderation • 3. Evaporative Cooling • 4. Significant Solvency

  7. Surface Tension • Surface Tension – water can stand above the rim of a glass due to hydrogen bonds • Is surface tension a result of cohesion or adhesion? • Why?

  8. Temperature Moderation Temperature – measure of average kinetic energy of molecules -- Water does this because it has a high specific heat  Water can absorb large amounts of heat but change little in temperature  Guess what type of bonding is responsible for high specific

  9. Sea Breeze? (cranberry juice & …) • Day, land heats up faster (low specific heat) • Air over land rises • Onshore breeze • Night, lands cools faster • Hot air rises over water • Offshore breeze

  10. Evaporative Cooling • Water has high specific heat due to? • Responsible for cooling • Heat is released as liquid is vaporized into gas • Highest energy molecules are vaporized first • Vaporization involves the breaking of which bonds?

  11. Hydrogen Bonding is cool

  12. Water • Which is more dense, liquid or solid H2O? • As temperature increases, what happens to density? • Why? • What does this mean for ocean stratification? • Which temperature (Celsius) is H2O the most dense?

  13. Properties of Water • 1. There are two cities, Davie and Pompano Beach, which will have a higher temperature during summer? • Why can we not use Weston instead of Davie? • 2. What bonds are broken during evaporative cooling? • 3. What force is responsible for cohesion? • 4. What force is responsible for adhesion?

  14. Like dissolves like… • Water is polar so it dissolves polar substances • Also dissolves ionic solids (salts) • Polar substances = hydrophilic • Hydro = water -philic = to like • (Dendrophiliac – one who likes trees) • Water does not dissolve nonpolar substances • Nonpolar substances = hydrophobic • Hydro = water -phobe = to fear • (Triskaidekaphobe – one who fears the number 13)

  15. Remember… • Hydrophilic = polar molecule • Will dissolve in water • Hydrophobic = nonpolar molecule • Will NOT dissolve in water • What about ionic compounds?

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