Properties of Water

1. Properties of Water • Polarity & H-bonds • Water Density • Water as a Solvent • Surface Tension • Heat (Sensible vs Latent) • Reynolds Number (Inertia to Viscosity) • Molecular Diffusion • Flow Type (Laminar vs Turbulent) • Light Attenuation

2. Water Density

3. Stratification by Temperature or Dissolved Ions (salts): Epilimnion Hypolimnion

4. Water as a SolventGeologic Weathering Solute solubility increases with increasing temperature due to increases frequency of molecular interaction and less H-bonding between water molecules and more hydration of solutes by water molecules. Gas solubility decreases with increasing temperature due to increased vibration and expansion of molecules plus the reduced partial pressure favors a gas equilibrium shift from water to air, something solutes don’t experience because water binds solutes electrostatically.

5. At water-air or water-solid interfaces molecules of water are nearly completely H-bonded together, like a molecule thick layer of ice. • This added tension force is utilized by many aquatic & semi-aquatic arthropods • It is also what explains waters ability to be drawn against gravity when in narrow spaces; capillary action. Surface Tension Water strider (right) Fishing Spider (left)

6. Sensible versus Latent Heat of Water Liquid water temperature responds in a constant manner as heat is added or removed; we call this sensible heat as we can make sense of heat change by measuring temperature change with a thermometer. However, no temperature change is seen upon removing the 80cal/g from liquid water at 0ºC to get ice at 0ºC. This is called the latent heat of fusion (freezing). There is also a latent heat of evaporation of 585 cal/g to get water to go to gas, i.e. energy needed to break all H-bonds.