Chem. Oceano. Unit 2: Water + Salt

3 Phases of Water

1) Liquid - oceans

2) Solid - ice + snow

3) Gas - water vapour

Properties of Water's Liquid Phase

1) Vast

2) Salty

3) Cold

4) Dark

5) Full of life

6) Never still

7) Noisy

Liquid Water

Consists of molecules that move relative to one another.

Gaseous Water

Consists of independently moving molecules.

Ice

Consists of ordered molecules that are tightly bonded to one another in a honeycomb lattice of hydrogen bonds.

Vast

97.4% of the volume of H2O on Earth is in the liquid form.

Salty

The mean salt water content is 34.72 g/kg of seawater.

Cold

The mean temperature of water is 3.52 C.

Dark

Light can only travel through a few 100s of m in H2O.

Full of Life

H2O is an essential/major constituent for all life forms + a good nutrient solvent.

Never Still

H2O is a highly mobile liquid.

Noisy

Sound can travel 1000s of km in H2O.

Properties of Water's Gas Phase

1) Clouds + fog

2) Advection fog

Clouds + Fog

Water vapour condensed to droplets/ice crystals.

More

The warmer the air is, the __________ water vapour it can hold before becoming oversaturated + condensating.

Advection Fog

Forms when humid air moves over cold land/water (ex. St. Johns in the winter + spring).

Properties of Water's Solid Phase

1) Sea ice

2) Icebergs

Sea Ice

Forms from seawater when temp. drops below -1.9 C.

Rejected

Salt from freezing seawater is ________________ from the forming ice, increasing the salinity of the surrounding H2O as brine (important for THC).

Icebergs

Form on land from valley glaciers in the Arctic or the calving of ice-shelves in the Southern Ocean.

Does Not

Melting icebergs add freshwater to the ocean, melting sea ice _______________.

0.91

The density of ice is _________ the density of liquid H2O, leaving 9% of an icebergs mass floating above the surface.

Ionic + Covalent Bonds

Bonds between atoms within the same molecules (stabilizes octets).

Ionic Bonds

Donate electrons to form anions and cations.

Covalent Bonds

Share electrons by attracting the positively charged nuclei of the two atoms (one side is more electronegative than the other).

Increases

Electronegativity ______________ as you move up and to the right on the periodic table.

Polar

Water is _____________ because O is covalently bonded with H and is more electronegative (2 positive poles (Hs) and 1 negative).

Attract

In liquid/solid water, molecules ____________ each other as the negative end of one is attracted to the positive ends of another molecules (ex. hydrogen bonding in H2O).

Hydrogen Bonding

The electrical charge attraction between a hydrogen atom and a highly electronegative atom (N, O, F) in the same molecule.

Different Molecules

Unlike covalent bonding, H-bonds occur between atoms of ___________________________.

Less

Opposite to most in the solid phase, ice is _____________ dense than liquid H2O.

Insulating

Because ice possesses a honeycomb structure, there is lots of empty space inside that exhibit ____________________ properties.

Melting, Freezing, + Latent Heat of Melting

Ice exhibits high ___________________________________________ (more energy) needed to break some H-bonds in melted.

High Specific Heat

The amount of heat needed to warm 1 kg of H2O by 1C.

Overcome

High boiling/evaporation/condensation temperatures are needed to ____________________ H-bonding.

Maximum Density of Freshwater

1 g/cm^3 at 4C.

Actual Density of Freshwater

Below 4C, proto-ice clusters form, lowering density.

High Surface Tension

Created when H-bonds form a web of molecules on the surface.

Low Compressibility

H-bonds restrict how many H2O molecules are pushed together.

Heat Capacity

The steeper a graphical slope, the lower the ___________________ is (g/C)

Melting + Boiling

In a plot of heat capacity transitions, the completely flat lines correspond to __________________.

High Dissolving Power

Polar substances have a _____________________________ and is linked to the asymmetric charges in H2O (why H2O is the universal solvent).

Unusual Physical Properties of Water

1) High specific heat

2) High latent fusion of heat

3) High Latent heat of evaporation

4) Thermal expansion/ density max above freezing (FW + brackish), max at freezing (SW)

5) High surface tension

6) High conduction of heat

7) Low molecular viscosity

Unusual Chemical + Biophysical Properties of Water

1) High dissolving power

2) Highest dielectric constant

3) Small electrolytic dissociation

4) High transparency

Factors Affecting Light in the Ocean

1) Height of the sun above horizon

2) Smoothness of sea surface.

65%

__________ of light entering the ocean is absorbed within the first 1 m + converted to heat.

1%

___________ of light entering the ocean reaches a 100 m depth.

First

Long wavelengths (red light) are absorbed _____________.

Last

Short wavelengths (blue light) are absorbed ______________.

Back-Scattered

The colour of the ocean we see (blue) is the light that is ________________ toward your eyes - everything else is quickly absorbed.

20 m

In turbid coastal areas, light can penetrate __________________.

Yellow-Green

In turbid coastal areas, water appears _______________________ because particles in shallow depths reflect these wavelengths before they can be absorbed + algae absorb blue light.

Increases

The speed of sound in H2O __________________ with temperature (salinity) + pressure.

SOFAR Channel

A zone of minimal sound velocity in the pycnocline (1 km deep) created by vertical variations in temp. + pressure.

Dispersion

The refraction of sound waves within the SOFAR channel prevents the _______________ of sound energy and objects here cannot be detected from the surface.

Zone of Silence

Sound waves travel 1000s of km within the channel with little/no drop-off signal (military, earthquakes, whale communication).

Density + Conductivity

Adding salt to water increases _____________________________.

Temperature + Freezing Point

Adding salt to water decreases __________________________ + disrupts H2O molecules from their tendency to form ordered groups.