• 1) HISTORY OF WATER CHEMISTRY. Empodocles (400 BC) said all matter was composed of 4 primary elements, Aristotle (300 BC) agreed; but Lavoisier (1783) showed water was divisible

• 2) UNUSUAL PHYSICAL AND CHEMICAL PROPERTIES OF WATER DUE TO POLARITY OF MOLECULE: MAKES IT "STICKY"

  • asymmetrical alignment of hydrogen atoms in water molecule causes polarity
  • covalent bonds- strong bond that shares electrons between atoms
  • hydrogen bonds- weak bond due to charge asymmetry between atoms or molecules; (they give clear ocean water it's blue color because they absorb red light preferentially)

• 3) WATER IS A REMARKABLE THERMAL BUFFER:

  • its heat capacity, latent heat of melting, & latent heat of vaporization are the highest of common liquids & solids
  • these have major consequences for global climate

• 4) WATER IS A REMARKABLE SOLVENT (can dissolve more substances than any other liquid)

• 5) ORIGIN OF SEAWATER AND MEASUREMENT OF SALINITY:

  • seawater is not just concentrated river water (ionic proportions differ: excess Cl- and Na+, deficient in Ca+2, CO3-2 and SiO2, in seawater)
  • arose initially via outgassing from earth's mantle ('juvenile water'; highly acidic due to excess Cl- and H+); still occurs at 0.1 km3/yr from mid-ocean ridges
  • proportions of ions in seawater are remarkably constant worldwide
  • salinity can be measured by CHLORINITY (salinity= 1.80655 * chlorinity; chlorinity= concentration of halide ions: Cl, Br, Fl, I), CONDUCTIVITY or SPECIFIC GRAVITY
  • salinity of open ocean is 35 g/kg of water= 35 parts per thousand

• 6) EFFECTS OF TEMPERATURE & SALINITY ON SEAWATER:

  • increasing temperature has 4 effects: a) increases solubility of ions, b) decreases solubility of gases, c) decreases viscosity, and d) decreases density
  • increasing salinity has 4 effects: a) increases density (major effect), b) decreases freezing point, c) decreases rate of evaporation (minor effect), and d) alters temperature of maximum density

For a cool paper modeling how quickly the arrangement of water molecules changes as water freezes see:

• Matsumoto,M. et al. 2002.
  Molecular dynamics simulation of the ice nucleation and growth process leading to water freezing.
  Nature 416, 409 - 413 (28 March)