Seawater properties

Question 1

Distribution of free water on Earth

Answer 1

Ocean - 97%
Ice caps and glaciers - 2%
Rivers, lakes, wetlands, grasslands - <1%

Question 2

Residence times

Answer 2

Ocean - 4,100 years

Atmosphere - 9 days

Question 3

Properties of the water molecules

Answer 3

polar

cohesion, adhesion, dissolution, capillary action

Question 4

cohesion

Answer 4

attachment of water molecules by hydrogen bonds

strong ‘skin’ on water surface

Question 5

dissolution

Answer 5

action of water molecule separating component elements

due to polarity

Question 6

adhesion

Answer 6

attachment of water molecules to other substances by hydrogen bonds
sticks to other stuff
sticks to solids (wetting)

Question 7

capillary action

Answer 7

e.g. cohesion, adhesion, tendency of water to spread if a textile is dipped in water

Question 8

Heat

Answer 8

energy produced by random vibration of atoms or molecules

Question 9

Temperature

Answer 9

The response of an object to the input or removal of heat energy

Question 10

Heat capacity

Answer 10

measure of heat required to raise the temp of one gram of a substance by 1 deg C

Question 11

Thermal inertia

Answer 11

tendency of a substance to resist change in temp

Question 12

Solvent

Answer 12

a substance capable of dissolving other polar molecules and ionic compounds
e.g. water

Question 13

Salinity

Answer 13

measure of dissolved solids in seawater
seawater of salinity of 35% means that 3.5% of the seawater is dissolved substances and boiling away 100kg of seawater produces 3.5kg of residue
ocean salinity is 33-37%

Question 14

constituents of seawater

Answer 14

origin: weathering of rock and input from deep crustal and upper mantle through volcanism
Na and Cl

Question 15

Trace element

Answer 15

less than 1%

Question 16

Dissolution of gases

Answer 16

gases from atmosphere dissolve in seawater at surface
found in different proportions due to different solubilities
increases with cold temp
N2 - 48%
O2 - 36%
C - 15%

Question 17

pH

Answer 17

Water separates to form H+ ions and OH- (hydroxide) ions

acids release H ions and bases combine with themchange of pH unit is a ten-fold change in ion conc

Question 18

Density of seawater

Answer 18

mass/volume in kg/m^3
pure water - 1000 kg/m3
seawater - 1020-1030
increases with salinity and pressure and decreases with temperature

Question 19

Ice formation

Answer 19

Freezing point of pure water 0 deg C
of seawater -2 deg C
sensible heat - heat exchange accompanied by temp change
latent heat - heat exchange without change in temp (change in state)
latent heat of fusion - heat removed from a liquid during freezing or added to a solid during freezing that produces state change but not temp change

Question 20

Vapor formation

Answer 20

evaporation - type of evap without reaching boiling temp
more energy needed to change water into vapor than vapor into ice
approx 50% of solar energy entering ocean results in evap

Question 21

Propagation of light

Answer 21

sunlight is reflected, scattered, and absorbed on its way to and across the ocean
reflection - change in direction of light to return to medium of origin
scattering - dispersion or bounce of light waves
absorption - conversion of light energy into heat
Water absorbs all EM radiation - top meters absob all wavelengthsbut violet, green, and blue travel deeper into water column

Question 22

Zones in water column

Answer 22

photic - thin film of lighted water on surface, 50-100m in depth but as deep as 600m, hosts most life
aphotic - dark, deep ocean that light cannot penetrate

Question 23

Propagation of sound

Answer 23

sound - a form of energy transmitted by rapid pressure changes in an elastic medium
sound intensity decreases with depth due to spreading (propagation away from source), scattering (bouncing off bubbles and particles and organisms), absorption (conversion to heat)
sound travels much more efficiently than light in water
1500 m/s - increases with temp and pressure
min sound velocity at 1000m
Refraction - bending of light or sound waves as they move at an angle other than 90 deg between media of diff optical or acoustic densities
SOFAR layer - layer of min sound velocity in which sound transmission is unusually efficient for long distances - refraction
sonar - sound navigation and ranging
active sonar - device that sends pulses of high freq sound and analyzes echoes (for dpth measurements, geol, etc.)