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Seawater (Properties of pure water vs salt water (Osmosis - water moves…
Seawater
Properties of pure water vs salt water
Salt water is electrically conductive; pure is not
Salt water has a slightly lower heat capacity
Salt water has a slightly slower evaporation rate
Salt water boils at a higher temperature than pure water
Salter water freezes at a lower temperature than pure water
Osmosis - water moves from areas with higher water concentration to areas with lower water concentration
Hypertonic - water rushes into a cell that high salt content
Hypotonic - water rushes out of a cell that has a low content
Isotonic - water and salt content balance inside and outside cell
Layers in the ocean
At the surface evaporation increases salinity
At the surface precipitation and river discharge decreases salinity
Density of seawater depends on temperature and salinity
Decreasing temperature and/or increasing salinity increases density
Surface layer - top layer of the ocean
Warm, low salinity and low density
May be absent at higher latitudes
Pycnocline - layer where density of water rapidly increases
Below surface layer
May be absent at higher latitudes
Themocline - increase in density due to rapid decrease in temperature
Halocline - increase in density due to rapid increase in salinity
Deep zone - bottom layer of the ocean
Cold, high salinity and high density
Ectotherms - animals have body temperatures the same temperature as their surroundings ("cold-blooded"). These animals may move slower in the deep zone.
Endotherms - animals can regulated their body temperature ("warm-blooded"). These animals can move faster, but need to consume more energy.
Water molecule
Has two hydrogen atoms and one oxygen atom, H2O
The atoms share electrons in a strong covalent bond
Water is a polar molecule
The hydrogen side of the molecule has an overall positive charge
The oxygen side of the molecule has an overall negative charge
Water molecules bond with each other hydrogen (positive charge) to oxygen (negative charge) using weak hydrogen bonds
Cohesion - hydrogen bond attraction between water molecules
Surface tension - skin on top of water's surface due to cohesion
Adhesion - hydrogen bond attraction between water molecules and different polar molecule substances
Hydrogen bonds between water molecules cause water to forms a crystal structure that makes water less dense as ice than it is as a liquid
Viscosity - how much a substance resists flowing
Decreasing the temperature of water increases its viscosity
Water has a very high heat capacity
It requires a lot of energy to heat up (heats up slowly)
It holds on to its heat energy for a long time (cools down slowly)
Areas near large bodies of water, like the ocean, is cooler in the summer (water heats up slowly) and warmer in the winter (water cools down slowly).
Thermal inertia - how much a substance resists changing temperature
Water has a high thermal inertia and does not change temperature quickly
Water has three states of matter
When water is changing states of matter the energy is being used to form or break hydrogen bonds, so TEMPERATURE DOES NOT CHANGE.
Latent heat of vaporization - heat absorbed to break ALL of the hydrogen bonds between water molecules and change water from a liquid to a gas
Most of amount of energy is needed for this change of state
Latent heat of fusion - heat absorbed to break SOME of the hydrogen bonds between water molecules and change water from a liquid to a gas
Dissolved gases in our oceans
Cold water is able to "hold" more gases than warmer water
Dissolved carbon dioxide (CO2)
Lower at the surface than it is a deeper depths because it is being used by plants and algae during photosynthesis. Photosynthesis does not occur a deeper depths.
Respiration by animals adds additional carbon dioxide to water
Carbon dioxide combines with water to form carbonic acid
Ocean water is slightly basic, alkaline, with a pH of around 8
The ocean is becoming more acidic as more carbon dioxide combines with water and lowers the pH
The dissolved ions makes seawater act like a buffer so that the pH does not change quickly
Seawater becomes more acidic as depth increases due to the increase in dissolved carbon dioxide
Dissolved oxygen (O2) is higher at the surface than it is a deeper depths because it is being made by plants and algae during photosynthesis. Photosynthesis does not occur a deeper depths.
Respiration by animals removes additional oxygen from the water
Dissolved nitrogen (N2)
Used by plants and algae to make different proteins
Animals eat the plants and algae to get the nitrogen "fixed" by the photosynthetic organisms
Light through layers of ocean
Red light is the first type of visible light to be absorbed and scattered. Blue light is the last type of visible light to be absorbed and scattered.
Organisms are often clear or red. The lack of red light makes them appear black in the water column
Photic zone - top layer of the ocean where enough light is present for photosynthesis to occur
Disphotic zone - middle layer of the ocean where there is some light, but not enough for photosynthesis to occur
Aphotic zone - bottom layer of the ocean where light does not reach
Seawater as a solution
Solution - contains solutes and solvents that are evenly dispersed among another substance
Solutes - substances being dissolved
Solvents - substances dissolving other substances
Water is known as the "universal solvent" because it dissolves so many substances
Mixture - combination of substances that are not chemically bonded or in fixed proportions
Homogeneous - has uniform appearance throughout
Heterogeneous - has visible different substances
Dissolved salts in our oceans
When water dissolves salt the hydrogen side of some water molecules pulls away the negatively charged chlorine ions of the salt crystal, while the oxygen side of some water molecules pulls away the positively charged sodium ions of the salt crystal
The oceans maintain an overall salinity of around 35 ppt. This is known as chemical equilibrium.
Ions are added to our oceans by river runoff, volcanic activity, groundwater, vents on the seafloor, and decay of once-living things.
Ions are removed from our oceans by entrapment as water percolates through seafloor features, sea spray, uptake by living organisms, incorporation into sediments, and subduction
By mass most of ions are chloride (Ca-). The second most abundant ion are sodium ions (Na+). This is because the chloride atom is larger than the sodium atom.
Principle of constant proportions states that no matter how much the salinity varies, the proportions of several key inorganic elements and compounds do not change.
Changing the amount of water will change the salinity, but not the relative portions of the different ions
Conservative constituents, like dissolved salts, follow the principal and spend the longest time in the ocean
Non-conservative constituents, like dissolved gases, do not follow the principal and spend the shortest time in the ocean.
Vary based on seasonal, biological or short geological cycles
Sound through layers of ocean
Sound travels farther than light can travel
Travels fastest through water than air
Travels generally faster through colder water than warm water
Travels generally faster through water under higher pressure
SOFAR layer - depth where sound can travel the farthest with the lowest amount of energy