The Physical Properties of Water

1. The Physical Properties of Water An Introduction to the World’s Oceans Sverdrup et al. - Chapter Five - 8th Ed.

2. Table 5.1 top

3. Table 5.1 bottom

4. The Water Molecule • H2O: two hydrogen atoms and one oxygen atom • Covalent bonds • Polar molecule • Hydrogen bonds

5. Temperature and Heat • Molecules in motion: solids, liquids & gases • increasingly disorganized • Average atomic or molecular kinetic energy measured by temperature in degrees of three scales • Fahrenheit (o F), Celsius (o C) or Kelvin (K) • 32 o F = 0 o C = 273.15 K ( freezing point of water ) • 212 o F = 100 o C = 373.15 K ( boiling point of water ) • 0 K = absolute zero • Heat: measure of the total amount of kinetic energy

6. Changes of State • Three states of water: solid, liquid and gas • dew point • Changes of state • Hydrogen bonds • Latent heat of fusion • 80 calories / g- o C • Latent heat of vaporization • 540 calories / g- o C • Pressure dependence • Depressed freezing/boiling • Sublimation – ice to vapor • Salinity effects

7. Table 5.2

8. Heat Capacity • Heat capacity: quantity of heat required to produce a unit change in temperature • Hydrogen bonds and high heat capacity of water • Stability of Earth’s temperature • High heat capacity • High latent heat of fusion • High latent heat of vaporization

9. Cohesion, Surface Tension, and Viscosity • Hydrogen bonds hold water together • Cohesion • Surface tension: measure of how difficult it is to stretch or penetrate the surface of a liquid • Viscosity: resistance to motion or internal friction • Effects of temperature on viscosity

10. Density • The effect of pressure • Water is nearly incompressible • Pressure increases with depth • Density increases with depth • The effect of temperature • Density decreases temperature • Density of ice • Density of moist air • The effect of salt • Density increases with salinity • Combined effect of temperature and salinity near the freezing point

11. Table 5.4

16. Dissolving Ability • Water is the “universal solvent” • Polar nature of water molecules

17. Transmission of Energy • Heat • Conduction • Convection • Radiation • Light • Electromagnetic radiation • Absorption, scattering, and reflection • Attenuation and Beer’s Law • Attenuation and wavelength of light • Sound • Speed of sound in seawater • Dissipation • Sound shadow zones • Sofar channel

18. Light & Sound • Scattering & absorption (attenuated) • frequency dependent • Photic & aphotic zones • Refraction • Sound also scattered and absorbed (attenuated) • frequency dependent • Velocity increases with salinity, P & T. • 1500 m/sec in H2O vs. 334 m/sec in air @ sea level • Speed of sound = (axial modulus/density) ½ • Deep Scattering Layer & other “organism” affects • The SOFAR layer (sound fixing and ranging) • SONAR (sound navigation and ranging)

19. Fig. 5.9 Attenuation of “Light” • Absorbed • By water • By organisms - photosynthesis • Scattered • Reflected

20. Table 5.6

22. Fig. 5.10 Refraction of Light

23. Secchi Disk

24. Marine Optical Buoy

25. Fig. 5.13 Travel time vs. depth d = ½ v t

26. Fig. 5.14 Precision Depth Finder

29. Acoustic Thermometry of Ocean Climate • Sound speed and travel time: function of temperature • Low frequency sound pulses can measure global warming • Effects on marine mammals

30. Ice and Fog • Sea ice • Formed by low air and water temperatures • Freezing seawater • Salt water in ice escapes over time • Icebergs • Formed by glaciers on land • Iceberg activity may be due to global warming, driving an increased rate of melting • Fog • Condensation of moisture forms clouds • Three types of fog • Advective fog—warm, water-saturated air passes over cold water • Sea smoke—dry, cold air moves over warm water • Radiative fog—warm, moist air cools at night

32. Fig. 5.18c,d

34. Green Icebergs • Color of icebergs normally blue to white • Green ice contains dissolved organic material from seawater • Formed by freezing seawater under ice shelves

35. The End