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Unique properties of water overview
 

Unique properties of water overview

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Hydrogen bonds, crystal lattice, specific heat, etc.

Hydrogen bonds, crystal lattice, specific heat, etc.

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    Unique properties of water overview Unique properties of water overview Presentation Transcript

    • The Water Planet
      • 97% of all water on our planet is in the oceans.
      • Fresh water represents the remaining 3% (2/3 is snow and ice in glaciers / polar ice caps).
      • Liquid and solid water cover roughly 3/4 of Earth's surface area.
      • 29% of the earth’s surface is above sea level (71% is below )
    • Unique properties of water
      Absorbs or releases more heat than most other substances for every temperature degree of change
      Water is a good solvent and can dissolve more substances than other fluids, even rocks
      Water exists in 3 physical states that can power thunderstorms/hurricanes and help transport the sun's energy, nutrients, and organisms
    • More than half the world's population live within 60km of a coastline
      South Florida, USA
    • Overview
      Chemical properties of water
      H bonds
      Ice
      Salinity and Sources
      Physical properties of water
      Biomechanics
      Density
      Temperature
    • Chemical properties of water
      Hydrogen Bonds
      Crystalline Structure
      Surface Tension
      Tensile Strength
      Specific Heat
      Evaporation
      Molecular Interactions
      Movement and Transport
    • Chemical properties of water
      Hydrogen Bonds
      Crystalline Structure
      Surface Tension
      Tensile Strength
      Specific Heat
      Evaporation
      Molecular Interactions
      Movement and Transport
    • Hydrogen Bonds
      d-
      O
      H
      H
      d+
      d+
    • Hydrogen Bonds
    • Hydrogen Bonds
      3 physical states of water:
      WATER VAPOR
    • Crystalline Structure
    • Crystalline Structure
    • Ice
    • d-
      O
      H
      H
      d+
      d+
      Surface tension
      Water has high surface tension due to lateral and downward attraction between individual molecules, which stretches the water's surface, creating a thin skin
    • Surface tension
      Water has high surface tension due to lateral and downward attraction between individual molecules, which stretches the water's surface, creating a thin skin
    • Surface tension
      • Water striders can walk upon the water's surface.
      • Members of the neuston depend upon the surface film of water for transport and food.
      • Liquid water on surfaces to which it does not adhere well "beads-up."
      • Surface tension of the water allows wind to push against it, generating waves in large water bodies.
      • [Detergents reduce the surface tension of water (by as much as 70%) and allows it to spread out on a surface.]
    • Tensile strength
      Water is strong under tension.
      The force needed to pull pure water apart can be as much as 3 x 107 Newtons/m2
      120 lbs = 530 Newtons
      Limpet attachment strength = 1 x 106 Newtons/m2
    • Specific heat
      Water can absorb a great deal of energy which goes to breaking hydrogen bonds but does not lead to measurable temperature increases.
      Because of the massive number of hydrogen bonds in water, it requires a lot of energy to see even a small change in water temperature.
    • Evaporation
       A water molecule makes the transition from a liquid phase into a gas phase.
      Because the escaping molecule had a higher than average energy level, it leaves the liquid cooler (lower in energy) upon evaporation.
    • Hydrogen Bonds - Summary
      • High heat capacity (1 cal/g/°C);
      • Heat of vaporization (540 cal/g);
      • Heat of fusion (-80 cal/g);
      • Solid less dense than liquid phase;
      • High surface tension
    • Molecular interactions
      Solutes
      Dissociation of Water Molecules
      KD = [H+][OH-]/[H2O] = 1.8 x 10-16M
      where KD is the dissociation constant (equilibrium constant) for the dissociation of a proton from a water molecule (the smaller the KD, the stronger the binding)
    • pH of solutions
      pH - an index of the relative concentration of H+ ions in solution
      [H+] = [OH-] = 10-7M in pure water([H2O] = 55 M)
      pH º -log10[H+]
      In pure water, pH = 7
    • pH of solutions
      The pH scale ranges from 0 to 14
      The higher the pH, the lower the [H+] (alkaline, basic solutions have a high pH)
      The lower the pH, the higher the [H+] (acidic solutions have a lower pH)
    • pH of solutions
      Examples:
      Gastric juice = 1.0 Seawater  8.0
      Orange juice = 4.3 Urine = 6-8.0
      Blood plasma = 7.4 Ammonia = 12.0
    • pH and the sea
      A difference in pH from 8 to 7.8 can significantly decrease coral growth rates
      Increased CO2 in the atmosphere lowers pH
      Active photosynthesis and nitrogenous waste excretion can increase local pH
    • Water as a polar solvent and Salinity
      Strong Electrolytes (substances that dissociate completely when dissolved in water - ions)
      Salts consist of ions:
            NaCl ® Na+ + Cl- salt
                          HCl ® H+ + Cl- strong acid
                            NaOH ® Na+ + OH- strong base
      For strong electrolytes, KDȴ
    • Water as a polar solvent
      Weak Electrolytes (substances that dissociate in water only to a small extent (KD»10-3M to 10-11M)
      H2CO3 H+ + HCO3- KD = 1.7 x 10-4M
      KD»10-3M to 10-11M
    • CO2(g)            CO2(aq)
      (CO2 from the atmosphere
      dissolves into seawater)
      CO2(aq) + H2O(l)            H2CO3(aq)
      (Carbonic acid)
      H2CO3           H+ + HCO3-KD = 4.2 × 10-7
      HCO3-    H+ + CO32-KD = 4.8 × 10-11
      CaCO3(s) + 2 H+(aq)            Ca2+(aq) + H2CO3(aq)
      Carbon dioxide-carbonate equilibrium
      bicarbonate
      carbonate
      • High CO2= low [CO32- ]
      Ocean acidification
    • Water as a polar solvent
      Because of its small size and polar nature, water dissolves many materials, more than any other liquid
      Oceans of water act as sink for CO2 molecules – leads to acidification
      Seawater contains almost every known naturally occurring element
    • Seawater constituents
      Component
      Concentration
      Percentage of Salinity
      chloride 
      18.98 
      55.03 
      sodium 
      10.56 
      30.59 
      sulfate 
      2.65 
      7.68 
      magnesium 
      1.27 
      3.68 
      calcium 
      0.40 
      1.18 
      potassium 
      0.38 
      1.11 
      bicarbonate 
      0.14 

    • Seawater constituents
      • Average ocean water has a salinity of 35.0
      • This means that 1000 g of average seawater contains 965 g of water and 35 g of salts.
    • Dissolved
      chemicals
      Wind, water, and
      ice erosion
      Biological uptake, or absorption of particles, or precipitation
      Eroded rock particles
      Wind, water, and
      ice erosion
      River and wind transport and deposition
      Sediments
      Volcanic ash and igneous rocks
      on land
      Fallout of volcanic
      ash over oceans
      Compaction and
      water loss
      Subduction, melting,
      and vulcanism
      Scraped of and uplifted
      ot subduction zone
      Sedimentary rock on oceanic crust
      Sedimentary rock on land
      Seawater constituents
    • Seawater constituents
    • Movement and Transport
      Diffusion – high concentrations  low concentration
      Air vs. water
      Mass transport – particles carried by fluid flow
    • Diffusion
      high concentration  low concentration
      C = concentration
      D = diffusion coefficient
      x = length
      t = time
    • Mass Transport
      high concentration  low concentration
    • Physical properties of water
      • Viscosity
      • Reynolds number, Boundary Layers, and Mass transport
      • Density
      • Temperature
    • Water as a fluid
      Fluid (flu·id) French fluide, from Latin fluidus, from fluere to flow; akin to Greek phlyzein to boil over):
       having particles that easily move and change their relative position without a separation of the mass and that easily yield to pressure; capable of flowing.
    • What is a fluid?
      Viscosity (m): the resistance of a fluid to motion or internal friction
      Reynolds number (Re): the ratio of inertial forces to viscous forces in a fluid
      Density (r): the mass of a substance per unit volume
    • Viscosity
      m = 1 x 10-3 N s/m2
      m = 50 N s/m2
      At 20º C
      m = 0.07 N s/m2
      At 100º C
      The viscosity of liquids can vary drastically and decreases rapidly with an increase in temperature.
    • Reynolds number
    • Reynolds number
      Re = rUx/m
    • Reynolds number
      Re = rUx/m
      Re = 108
      Re = 1
    • Copepod swimming
      Low Re
    • Boundary Layers and Mass Transport
      Re = 101
      Laminar
      Turbulent
    • Boundary Layers
    • Boundary Layers and Mass Transport
      Re = 103
      Re = 108
    • Density
       the mass of a substance per unit volume
    • Temperature
    • Temperature
    • Thermoclines