Week 3- Seawater Flashcards
Polar molecule
Attract particles with negative and positive ends
ex. water molecules creating hydrogen bonds
Cohesion
Water attracts water creating surface tension (hydrogen bonds)
- Explains why there are droplets of water
Adhesion
Stick to surfaces
- Electrostatic bonds
Why is water considered a universal solvent?
Bc it is a polar molecule
Kinetic energy
Energy an object has bc of its motion
- Water in all states creates kinetic energy
Heat
Amount of energy tranferred from one body to another due to temperature differences
Calorie
Amount of heat required to raise the temp of one gram of water by 1 degree celcius
Temperature
A direct measure of av kinetic energy of the molecules that make up a substance
(response to addition oor removal of heat)
Water in solid state
Molecules vibrate and stay in same position
Water in liquid state
More kinetic energy, bonds are starting to be broken
Water in gas state
More kinetic energy, all bonds broken
Heat capacity
Measure of the heat required to raise the temp of 1 gram of a substance by 1 degree celcius
Low heat capacity
Sand
Heats up quickly
High heat capacity
Water
Heats up slowly
*One of the highest heat capacities on the planet
Latent heat
When water undergoes a change of state a large amount of heat is absorbed or released
Latent heat of condensation
Energy released to atmosphere when going from water vapour to liquid
*Powers tropical storms
Thermostatic properties
Act to moderate temp changes and maintain bearable temp on earth
Global thermostatic effects
Transfers heat from the tropics towards the poles
Moderates global temp
Density of pure water
1.0g/cm3 at 3.98 degrees celsius is the max
What happens to density as heat is removed from water?
It increases
What happens to water when density is at its max?
Water molecules start to occupy less volume and water undergoes a phase change
What happens to the density of water as it freezes
It expands and density decreases
Why does ice float?
Forms a crystal lattice structure and is less dense than water
How many mols does a liquid have in its crystal lattice structure?
27
How many mols does a solid have in its crystal lattice structure?
24
What is the bond angle of the crystal lattice structure of water?
105 to 109 degrees
What percentage of sea water is pure?
96.5% pure water
3.5% dissolved solids
What does the presence of dissolved solids do to freezing point of seawater?
Reduces freezing point to -1.91 degrees celsius and lowers latent heat by 4%
Why is salinity important?
Make life in ocean possible
Affects ocean circulation
Provides info about palaeo-oceanic conditions
What is salinity?
Total amount of solid material dissolved in water, including dissolved gasses
How much salinity in one kilogram of seawater?
34.4% parts per thousand
Major ions representing 99% of all dissolved solids
- Chlorine
- Sodium
- Sulphate
- Magnesium
- Calcium
6.Potassium - Bicarbonate
What is the most dominant component in seawater?
Chloride (19.4 g/kg)
Major dissolved gases in seawater
- Nitrogen (48%)
- Oxygen (36%)
- Carbon dioxide (15%)
Solubility
Amount of a dissolved gas that the water can hold under a particular set of conditions
Saturation
Amount of gas currently dissolved in water
Undersaturated
More gas can dissolve
Saturated or supersaturated
Gas may be released
Are most gases saturated in the ocean?
Yes, such as nitrogen
Not O2 and CO2 bc they’re rapidly used by organisms
When does solubility of a gas increase?
With increasing pressure and decreased temp
ex. as we get deeper we dissolve more N and O2
Why does the amount of O2 decrease as we get deeeper?
- O2 comes from atmospheric diffusion (happens at surface)
- Organisms that perform photosynthesis create O2 using sunlight which happens close to surface
What happens to CO2 as we get deeper?
It increases
What does OML/OMZ stand for and how deep is it?
Oxygen minimum layer or zone
200-1000m
What is the OML/OMZ?
When O2 saturation is at its lowest
- No input from atmosphere or photosynthesis
- Output via respiration and decomposition
O2 saturation Atlantic vs Pacific
Pacific has a lower amount of dissolved O2
Atlantic has newer water molecules that allow for O2 to dissolve
How do we measure salinity?
Salinometer
Measures the electrical conductivity of seawater
Chloride in ocean
Accounts for 55% of total proportion of dissolved solids anywhere in ocean
What equation can we use to find salinity?
Salinity= 1.80655 x chlorinity
Principle of constant proportions
Ration of dissolved solids in the ocean is constant no matter where you are
**Forchhammer’s principle
Ratio of dissolved solids
Chloride= 55%
Sodium = 30.6%
Sulphate= 7.7%
others ones are small
How do ions enter the ocean?
- River discharge
- Volcanic eruptions
- Hydrothermal activity in mid-ocean ridge
Residence time
Average length of time that an ion spends in the ocean
- Times vary depending on how chemically active an ion is (More chemically active= less likely to stay in same form for a long time)
Dissolved solids in seawater vs freshwater
Chloride is 10.1% in fresh water and other compositions are very different from sea water
**due to residency
Longer residence times
More abundant in the ocean
ex. the most abundant dissolved solids in the ocean have long residence times
Why isn’t the ocean getting saltier?
Removal rate of ions= addition rate of ions
How are ions removed from the ocean?
- Biological processes (coccolithophores), absorption and precipitation
- Sea spray
- Biological processes
- Hydrothermal activity at mid-ocean ridge
What decreases salinity?
Adding water
- River discharge/run off
- Melting ice
- Precipitation
What increases salinity?
Removing water
- Evaporation
- Formation of sea ice
Halocline
Layer of rapidly changing salinity with depth
Salinity at higher latitudes
Salinity increases with depth
Salinity at lower latitudes
Salinity decreases as depth increases
What is sea water density?
1.022 to 1.030 g/cm3
*Increases with depth
Three main density zones
- Surface zone
- Pycnocline
- Deep zone
Surface zone of sewater
Density and salinity don’t change much
Pycnocline
Depth of seawater at which density rapidly increases
Deep zone of seawater
Density doesn’t change much
Temp and density
Temp increases, density decreases
Salinity and density
Salinity increases, Density increases
Pressure and density
Pressure increases, density increases
Latitude and changes to seawater
As latitude increases, its colder and surface zone and pycnocline don’t extend to the poles
What has the greatest influence on density?
Temperature
What is the pycnocline also considered?
A thermocline
Rapidly changing temperature in this zone (decreases with depth)
