In-Depth Notes on Water and Seawater Chemistry

The Unique Nature of Water

• Basis for life on earth
  • Human body consists of approximately 60% water
  • Marine organisms contain about 80% water, with specific examples like jellyfish being 95% water
• Molecular Composition
  • Water is composed of three molecules:
  • 2 hydrogen atoms (H)
  • 1 oxygen atom (O)

States of Water

• Water exists in three states:
  • Liquid
  • Solid (ice)
  • Gas (water vapor)

Heat Properties of Water

• Heat Storage
  • Water temperature changes slowly and holds temperature well
• Ice Formation
  • Few hydrogen bonds break at low temperatures, causing water to become less dense as it freezes
  • Stabilized hydrogen bonds cause water molecules to be held farther apart, which results in lower density of ice compared to liquid water
• High Heat of Vaporization
  • At high temperatures, hydrogen bonds can be broken, requiring a significant amount of energy to vaporize water due to the need to break multiple hydrogen bonds

Seawater Composition

• Major Sources of Salts in Seawater
  1. Rocks on land
  2. Earth's interior
• Seawater Temperature
  • Varies from -20 to 86°F (-29 to 30°C)
• Average Ocean Salinity
  • Average salinity is about 35 PSU (Practical Salinity Units)
  • Variations in salinity by location:
  • Red Sea: 40 PSU
  • Baltic Sea: 7 PSU
  • Pacific Ocean: 34.5 PSU
  • Factors affecting salinity include precipitation, evaporation, and freezing

Thermocline

• The thermocline is a transition layer of water in the ocean characterized by a steeper vertical temperature gradient than that in layers above and below it.