Figure 3.0 Earth

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Figure 3.0 Earth
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Water It IS important

• While adaptation to the environment through
  natural selection does occur for life to exist
  at all, the environment MUST be a suitable abode
• Water is a HUGE contributor to the fitness of
  Earth for life

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The water molecule

• Bent
• Polar
• Opposite charges on opposite sides
• Can form H bonds with up to four neighbors
• Emergent properties
• Due to the H bonding ? structured organization of
  molecules

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Properties

• Cohesive
• High surface tension
• Beading
• Adhesive
• High specific heat
• Stabilizes air temperature by absorbing heat
• Can absorb lots of heat with only a small rise in
  temperature due to H bonds
• Must break bonds before temp increases ?
  increased molecular motion.

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Phases of water

• High specific heat (1 cal/goC) will absorb a
  great deal of energy before changing phase
• http//mutuslab.cs.uwindsor.ca/schurko/animations/
  waterphases/status_water.htm
• What happens when it freezes?

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Figure 3.1 Hydrogen bonds between water
molecules 
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Figure 3.3 Walking on water
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Additional Properties

• High heat of vaporization
• 540 cal/g of water needed for water to evaporate?
  high boiling point
• On earth Solar heat is absorbed by the oceans and
  then is consumed by evaporation? heat released ?
  condensation
• RESULT evaporative cooling (hottest molecules
  leave first!

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Figure 3.4 Evaporative cooling
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Figure 3.x1 Water
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Specific Heat and the Oceans

• Absorb a lot of heat with little change in
  temperature
• Can release heat at night (lots for a little
  change in water).
• Stabilizes climates!

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Why does ice float?

• Think about cohesive properties of water
• What causes this?
• How is it related to surface tension.
• Why does it float??

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Figure 3.5 The structure of ice (Layer 2)
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Figure 3.5x1 Ice, water, and steam
Changing phases meakes seasonal transitions less
abrupt ? acclimation of organisms to the
environmental changes WATER IS A GOOD MODERATOR!
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Figure 3.6 Floating ice and the fitness of the
environment
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Figure 3.6x2 Ice floats and frozen benzene sinks
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Figure 3.7 A crystal of table salt dissolving in
water
http//programs.northlandcollege.edu/biology/Biolo
gy1111/animations/dissolve.html
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Water as a solvent

• Dissolves polar compounds
• Creates homogenous mixtures
• Solutions (solvent/solute)
• What are hydrophilic compounds
• Usually ionic or polar
• Affinity for water
• Doesnt have to dissolve

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Figure 3.8 A water-soluble protein
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Acids, Bases, pH

• Dissociation of water molecules
• Form hydronium and hydroxide ions in very small
  amounts
• Ions are very reactive and can disrupt a cells
  proteins and other molecules
• Generally ions are balanced but if an acid is
  added Hydroniums increase, a base reduces
  hydrogen ion concentration.

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Acids

• pH - log H
• Neutral 10-7 M
• pH - -7 7
• Buffers minimize changes in the concentrations
  of H or OH-
• ACCEPT OR DONATE H WHEN NEEDED
• Example carbonic acid ? bicarbonate ion and
  hydrogen

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Unnumbered Figure (page 47) Chemical reaction
hydrogen bond shift
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Figure 3.9 The pH of some aqueous solutions
http//www.johnkyrk.com/pH.html
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Acid Rain

• pH 5.6 (normal rain)
• lt 5.6 ? acid rain
• Causes
• Sulfur oxides and nitrogen oxides (fossil fuels,
  factories, automobiles)
• Result
• Dec pH ? dec solubility of minerals
• Some minerals wash out. Some (aluminum) become
  toxic)

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Figure 3.10 The effects of acid precipitation on
a forest
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Figure 3.10x1 Pulp mill
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Figure 3.10x2 Acid rain damage to statuary, 1908
1968