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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 _________ ? How does Cohesion differ from Adhesion?

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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 _________ ? • How does Cohesion differ from Adhesion? • 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 – • Is surface tension a result of cohesion or adhesion? • Why?

  8. Temperature Moderation Temperature – measure of -- Water  Water can  Guess what type of bonding is responsible for high specific heat?

  9. Sea Breeze? (cranberry juice & …) • @ Day, • Air • Onshore breeze • @ Night • Hot air • Offshore breeze

  10. Evaporative Cooling • Water has high specific heat due to? • Responsible for cooling • Heat • Highest energy molecules • Vaporization involves the breaking of which bonds? • Conversely, when water vapor condenses, which bonds are formed?

  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 • Also dissolves • Polar substances = hydro • Water does not dissolve • Nonpolar substances = hydro • Hydro = water

  15. Remember… • Hydrophilic = ____ molecule • Will • Hydrophobic = _____ molecule • Will • What about ionic compounds?

  16. Acids & Bases • Hydrogen ion = _____ = _________ (H3O+) • Hydroxide ion (OH-) BUT only 1 in 554,000,000 H2O molecules is dissociated!!

  17. Definitions • There are 3, but we use the simplest, the Arrhenius definition • An acid_________________________________, it ______________________(ionizes) • A base________________________________, it ______________________________(ionizes) • HCl H+ + Cl- Acid or Base? • NaOH Na+ + OH- Acid or Base? • H2O  H+ + OH- Acid or Base?

  18. Acidic / Basic Solutions • @ 25⁰C, the product of [H+][OH-] = 10-14 • IF [H+] = [OH-], then [H+] = 10-7 • Called a ___________ as the amount of acid ___ base • IF [H+] > [OH-], then [H+] > 10-7 • Called an __________ as the amount of acid ___ base • Remember 10-6 OR 10-4___ 10-7 • IF [H+] < [OH-], then [H+] < 10-7 • Called a __________ as the amount of acid ___ base • Remember 10-8 OR 10-10___ 10-7

  19. pH Scale • pH = -log [H+] pOH = -log [OH-] • So for pH, just take the exponent of the [H+] • Guess what you should do for pOH? • If [H+] = 10-6, what is pH? • If [OH-] = 10-5, what is pOH? • AND just as [H+][OH-] = 10-14, pH + pOH = 14 • IF pH = 8, then pOH = ?? • IF pOH = 9, then pH = ??

  20. Buffer • … substances that _________________ • Mammals have a pH blood buffer, called the _______________ • H2CO3 HCO3- + H+ • What happens when acid enters? • What happens when base enters?

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