Lecture 13: Water on Earth Flashcards
(11 cards)
How much water is present in the hydrosphere?
Hydrosphere = 1.4 x 10^9 km3
Where is the water on earth stored?
Water in air and soil moisture - 0.001%
Surface water (lake, rivers) - 0.022 %
Groundwater - 0.400 %
Icecaps and glaciers - 2.380 %
TOTAL FRESHWATER - 2.8%
What’s the rest, then? - 97.2% Ocean
Describe waters covalent bonding:
Hydrogen bonds are about 10% as strong as covalent ones
Results: surface tension, capillarity, adhesion, and blue colour
what is cohesion?
Cohesion is the tendency for like particles to stick together
What is adhesion?
Adhesion is the tendency for unlike particles to stick together
Describe water tension:
the attraction of water molecules to each other (cohesion) …
is greater than their attraction to molecules in the air (adhesion)
Water has a higher surface tension than most liquids
What makes up sea water?
Seawater is about 96.5% H2O
Seawater is a soup of chemicals
Cations, anions and compounds
Concentration is determined by: sources, cycles, transport, residence time, chemical reactions
Difference between dissolved and suspended material
Where do these compounds found in seawater come from?
From rocks: water is a powerful solvent
DOWN: Weathering of land rocks, transport by water, meteorites, rain, wind-blown
UP: Mid-ocean ridge brines and other hydrothermal vents, underwater lava
So why is the ocean not getting saltier and saltier?
Compounds are removed by: biological activity, settling, precipitation
Do salinity’s differ due to different salts?
No matter where you collect seawater, and no matter what its overall salinity is, the proportions of major salts are about the same
They are called “conservative elements”
Cl- Na+ SO42-
Mg2+ Ca2+ K+
Mixing is faster than changing inputs/outputs
Overall describe fresh water in terms of freezing point, cooling and evaporation, Density, material and ph.
Freshwater
Freezing point = 0°C
Cooling freshwater increases in density to 4°C, then decreases, then freezes
Freshwater evaporates quickly
Density is determined by T
and P
A predictable and
homogeneous material
pH = about 7
Overall describe sea water in terms of freezing point, cooling and evaporation, Density, material and ph.
Seawater
Freezing point typically about -1.9 °C
Cooling seawater increases in density till it freezes
Seawater evaporates more slowly than freshwater
Density is determined by T, S and P
A very mixed soup of chemicals
pH = about 8.1
