1. PHYSICAL PROPERTIES OF SEAWATER

2. How Unique is Water?
Water is one of only 3 naturally occurring liquids (mercury and ammonia)
Only substance occurring naturally that exists in all 3 states – solid, liquid, and gas – on Earth’s surface
Extremely large liquid range (0oC - 100oC)
Expands, becomes less dense as a solid

3. The Nature of Pure Water
Water made of 2 hydrogen atoms and 1 oxygen atom
Water is a polar molecule (+ end & – end)
Water’s unusual structure causes them to “stick together”
Water molecules form hydrogen bonds
Hydrogen bonds not very strong, but make water different from any other substance on Earth

4. Figure 3.1

5. Water has… Cohesion – sticks to itself Adhesion – sticks to others
Surface Tension – a measure of how difficult it is to stretch or break the surface of water
No waves without surface tension

6. Water has… Low Viscosity – little resistance to flow
Good for Earth’s marine organisms – WHY?

7. The Three States of Water
Water is the only substance that naturally occurs as a solid, liquid and gas on Earth
Evaporation absorbs heat
Condensation releases heat

8. Water is Weird Density – the mass of a certain volume of a substance
Solid water is less dense than liquid water
Water becomes more dense as it cools
Water is most 4º C
Becomes less dense as it nears 0º C
Good for the planet – WHY?

9. Heat Capacity
The amount of heat required to raise the temperature of 1 gram of a substance 1º C
Water has one of the highest
1 calorie raises 1 gram of water 1º C
It absorbs large amounts of energy before the temperature changes
Good for earth’s climate – WHY?

10. Changes of State Latent Heat of Fusion / Melting –
The amount of heat required to melt a substance without change in temperature
80 calories per gram

11. Changes of State Latent Heat of Vaporization / Condensation–
The amount of heat required to change a substance from a liquid to a gas without change in temperature
540 calories per gram

12. Why is Water Important? Water is the universal solvent
Water can dissolve more than any other natural substance
Water can dissolve many hydrophilic substances
Ionic compounds
Other polar compounds
Form “spheres of hydration”
Sphere of Hydration Video

13. Figure 3.5

14. Seawater has dissolved solids…
Source –
Chemical weathering of crustal rocks
Hydrothermal vents
From volcanic eruptions

15. Water … Density of pure water is 1 g/mL @ 4º C
Density of seawater is g/mL @ 4ºC
Density is determined by temperature and salinity
Seawater gets denser as it gets saltier, colder or both
Because temperature varies more than salinity, density is controlled by temperature

16. Density… Changes with depth Densest water sinks
Ocean becomes layered, stratified
Seen in profiles of salinity, temperature, and density
The greater the difference in density between surface and deep water, the more stable the water column and the harder it is to mix vertically

17. Figure 3.31

18. Pressure…
Water is noncompressible – does not change volume with increasing pressure
So is seawater
Pressure increases with increasing depth
Has small effect on volume
1 atm (14.7 lbs/in2) for every 10 m (33 ft)
Pressure in deepest trench ~1100 atm
As pressure increases, gases are compressed

19. Figure 3.13

20. Buoyancy
The ability of an object to float by displacing a volume of water equal to its own weight

21. Water… Transmits energy
Heat
Light
Sound
Refraction – the bending of light and sound waves due to density differences that affect the speed of energy transmission
increases with increasing salt, decreases with increasing temperature

22. Water… Transmits heat energy by Conduction – molecule to molecule
Convection – moving fluids & density driven
Radiation – direct from source (sun)

23. Water is … Transparent – transmits light energy readily
Important for photosynthesis
Oceans are blue because blue light penetrates the deepest
Coastal waters sometimes green because blue absorbed

24. Water… Transmits sound faster & farther than in air
1500 m/s in seawater (& 60 times farther)
334 m/s in air
At 1000 m combination of salinity, temp & pressure creates a zone of minimum velocity for sound – the Sofar Layer (sound fixing and ranging layer)
Sound waves produced here do not escape & travel long distances

25. SOFAR Channel