Sea water basic concepts - 2 Flashcards
What bonding is found in a water molecule?
Covalent
What are the 5 unique properties of water?
- Higher melting point
- Higher boiling point
- High heat capacity
- Greater latent heat of melting and vaporisation
- Great solvent power
What shape is water molecule?
Asymmetrical
To what degree are the hydrogen molecules separated when water is in its gaseous or liquid form?
105º
To what degree are the hydrogen molecules separated when water is ice?
109.5º
What causes the dipole structure of water?
Asymmetry and distribution of electrons
Which end of the water molecule is slightly positively charged?
Hydrogen end
Which end of the water molecule is slightly negatively charged?
Oxygen end
What kind of bond is created between water molecules due to the dipole structure?
Hydrogen bong (weak electrostatic bond)
How do water molecules cluster together?
In a hexagonal pattern
At what temperature does water reach its maximum density?
3.98ºC
What happens to water below 3.98ºC?
Increasing number of water molecules form hexagonal polymers, decreasing density
What happens to water above 3.98ºC?
Molecules are increasingly energetic and move further apart, decreasing density
How much less dense is ice compared to water?
8%
How does water dissolve salts?
Surround the atoms and neutralise ionic bonds
What do dissolved salts produce?
Anions (-ve) and Cations (+ve)
Define hydration
Process of water surrounding an ion
Define hydrolysis
Process of water breaking bonds that hold other molecules together
In what two ways does salinity affect sea water?
- Affects maximum-density
2. Affects freezing point temperature
How does the addition of dissolved ions affect water?
Lower initial freezing point temperature
Define salinity
The total mass, expressed in grams, of all the substances dissolved in one kg of sea water
What is salinity measured in?
Parts Per Million (ppm)
What is the average salinity of the ocean?
35 ppm
What % of salt ions is from sodium and chlorine?
86%
99% of all the salt ions in the sea are …
Sodium, Chlorine, Sulfate, Magnesium, Calcium, Potassium
Major constituents show little variation over time so are …
Conservative Property of seawater
What are the major nutrients in the ocean?
Nitrogen, Phosphorous, Silicon
Nutrients are scarce so are …
Nonconservative Property of seawater
What are the major gases in the sea (in decreasing abundance?)
Nitrogen, Oxygen, Carbon dioxide, Noble gases: Argon, Neon, Helium
How can we describe the state of salinity in the ocean?
Steady-state (input is equal to output)
What are the sources of salt to the oceans?
- Weathering of rocks on land
2. Reaction with lava
What are the sinks of salt from the oceans?
- Evaporation creating brine … evaporite beds formed
- Wind-blown spray then adsorption by clays
- Shell formation by organisms
- Subduction
Why is river water and sea water composition different?
Residence times vary (ions with long residence times accumulate in the oceans)
What is the heat capacity of water?
4.2 kJ/kgºC
What is the residency time of chlorine?
Infinite
What is the resident time of sodium?
260 x10^6 years
What is the maximum solubility of sea water?
360 g/L
What is the principle of constant proportion?
Ratio of any two major constituents is a fixed value, regardless of salinity
Salinity=
1.80655 x chlorinity
What does a salinometer do?
Indirectly measure salinity by measuring the electrical conductivity of water
