1. PHYSICAL PROPERTIES OF WATER

2. How Unique is Water?
Water is one of only 3 naturally occurring liquids (mercury and ammonia) on Earth
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. Water is a polar molecule – it has a positive and negative end

5. Figure 3.1
Hydrogen Bond – attraction between positive end of one water molecule and the negative end of another

6. 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

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

8. 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

9. 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?

10. 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?
Point Pleasant
Mohave Desert

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

13. Figure 3.5

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

15. Exploring the Density of Water Lab
Review your notes – What is unique about water’s density as solid/liquid?
At what temperature is water densest?

16. JQ: What is a hydrometer? How does it work?

17. Density… Pure Water less dense than salt water
Warmer water less dense than colder water
Denser near poles or equator?

18. Density… Density increases as you go deeper
Ocean is 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

19. Figure 3.31

20. Pressure…
Water is noncompressible – does not change volume with increasing pressure
Pressure increases with increasing depth
1 atm (14.7 lbs/in2) for every 10 m (33 ft)
Pressure in deepest trench ~1100 atm
As pressure increases, gases are compressed (remember “The Bends”?)

21. Figure 3.13

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

23. 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
The denser the water, the greater the refraction

24. Archer fish – evolved to account for refraction in order to hunt
Link
Archer fish – evolved to account for refraction in order to hunt

25. 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

27. 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

28. Sofar Channel