Water & Life Chapter 3
Dec 26, 2015
Slide 2 of 16
H2O is why we are here
H2O molecules are polar What does their polarity contribute to?
Each H2O molecule can form __ Hydrogen bonds?
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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?
Slide 6 of 16
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?
Slide 7 of 16
Properties of Water
1. High Surface Tension
2. Temperature Moderation
3. Evaporative Cooling
4. Significant Solvency
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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?
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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
Slide 10 of 16
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
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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?
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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?
Slide 14 of 16
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?
Slide 15 of 16
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)