week 3-lily Flashcards
Water: the molecule
H2O - 2 hydrogen atoms for every 1 oxygen atom
how is H2o held together by
covalent bonds
h2O covalent bonds (about them)
- strong bonds (lots of energy to break them)
- 2x lone pair electrons on oxygen
- “bent” shape of water molecules (104.5 degrees) between the hydrogen molecules
- creates polarity (dipolar) of water
dipolar
two poles
Water is a ____ molecule
polar
what does Water is a polar molecule mean
means that it has an unequal distribution of electrical charge across the molecule (positive and negative ends)
- due to difference between size of H and O atoms
- lone pairs push the hydrogen atoms to one “side” of the molecule
- angle is less than bonded tetrahedral
- lone pairs created greater repulsion
shape of water
critical for its lattice structure
lattice structure
- better frozen (doesn’t move)
- happens because of o2 binding with hydrogen from other water molecules
what is the binding of hydrogen with other molecules called (oxygen of other molecules)
hydrogen bonds
Electronegativity (Χ):
measure of an atom’s ability to draw electrons in bonding
Electronegativity of water module :Large difference (1.4) =
polarity
- which means the bond is polar (electrons aren’t shared equally).
oxygens Electronegativity
ΧO = 3.5
hydrogens Electronegativity
ΧH = 2.1
ΧO = 3.5 ; ΧH = 2.1 what does this mean?
oxygens pulls much harder than Hydrogen
Intermolecular H-bonding
between H in one water molecule and O in another
Covalent (intramolecular) bonds
(which holds H and O together in one water molecule) is super strong.
which bond is stronger, intermolecular or intramolecular
Covalent (intramolecular) bonds much
stronger than intermolecular bonds
what does the bonds of water result in
properties of cohesion and adhesion
- also makes the water “universal solvent”
universal solvent
ability to dissolve polar and ionizable solutes
what are the strongest intermolecular bonds?
H-bonds
where do H-bonds form
between hydrogen and elements with high electronegativity
what is the strongest H-bond
H-F (Xf= 4.0)
also H-N, and H-O
what are intermolecular bonds responsible for?
- Cohesion – Water sticks to itself (why you get water droplets).
- High Specific Heat Capacity – Water absorbs a lot of heat before it changes temperature (they dont want to change temp much because you have to break bond which takes alot of energy)
- Earth’s Energy Balance – Water’s ability to absorb, store, and release heat
Cohesion
water attracts water; surface tension
Adhesion
‘stick’ to surfaces
What is a solvent?
- Ability to dissolve more substances than most any other liquid
- Particularly important for “salty” ocean water
sodium chlorides
Na+–> sodium ion (a cation)
CL- —> an anion
ions
atoms with an unbalanced charge
- difference between # of electrons and # of protons
- held together by electrostatic attraction (ionic bonds)
what is a water
universal solvent
water being a universal solvent
Water molecules can reorient themselves based on the charges of dissolved solutes. This means that water molecules adjust their positions to interact with different types of substances.
substance that dissolve water can be
- ionic compounds (NaCI)
- intermolecular
thermal properties of water
- Water exists naturally in all three states (solid, liquid, gas) in the environment
- Play crucial role in circulation and other ocean processes
- Storehouse for heat energy
water going from solid –> liquid–> gas
ice: molecules locked in place
liquid: molecules move freely (due to melting)
gas: independent molecules (due to vaporization/evaporation)
what does melting, vaporization, and sublimation (solid to gas) absorb
heat and cool the environment
what does freezing, condensation, and deposition release and do?
releases heat when going into these forms and warm the environment
what happens to the bond when water is changes phases?
- need to break or create bond to change from one phase to another (requires alot of energy)
- do this by removing (forming bonds) or adding (breaking bonds) energy
Heat is
ENERGY: or the amount of energy transferred from one body to another due to a difference in temperature
what is heat proportional to
average kinetic energy
units for heat/energy
joule (J)
Temperature (T) is
direct measure of the average kinetic energy of the molecules that
make up a substance
- object’s response to an input (or removal) of heat
unit of temperature
kelvin
absolute zero
0k = -273.15 degrees Celsius
example of conversion from kelvin to celsius
(remember: Δ1 K = Δ 1oC)
TemperatureinK=Temperaturein°C+273.15
- 20°C = 293.15 K
very hot day, middle of summer what is happening with water and sand?
water is still cold
sand is very hot
very hot day, middle of summer why is water still cold
heats up slowly – high specific heat capacity
very hot day, middle of summer why is sand is very hot
heats up very quickly – low specific heat capacity
Very cold day, middle of winter what is happening with water
water can be much warmer than air (retains heat longer)
- higher specific heat capacity
Temperature difference can cause oceans and lakes to
steam- (water vapor- releasing heat from water)
Measure of a substance’s ability to absorb (and hold) heat
SI Unit = 4.184 kJ / kg / K
pure water has a very high heat capacity- what is it
(4.184 kJ / kg / oC)
Specific heat capacity of Iron (Fe)
451 J· kg-1· K-1
takes alot of time for water to heat up or cool down; why?
sensible heat and latent heat
Sensible Heat:
Energy that changes the temperature of water without changing its state (solid, liquid, gas).
- the heat capacity of H20
Latent Heat:
Energy that changes the state of water (e.g., from liquid to gas) without changing the temperature.
to change from one phase to another of water;
heat energy must be either absorbed or released
- energy is required/lost to break/ form H-bonds
breaking or forming of H-bonds is
latent heat
(freezing/melting & evaporating/condensing)
specific heat capacity & latent heat graph
refer to page 21 and 22 of lecture 3.
liquid going to solid
more condensed phases
liquid going to gas
less condensed phases
heat removed from the tropical oceans (evaporation latitudes)
- is carried toward the poles and is released at higher latitudes through precipitation (at the precipitation latitudes)
why does ice float
due to density and thermal properties
- water temp, salinity and pressure matters
pure water density
1.0g/cm3
water becomes less dense as it cools down
ice is less dense than liquid water that’s why it can float
density at 20 degrees celsius (density slowly increasing as heat is removed (up til 4 degrees) why?
- removing heat
- molecules move more slowly and pack closer together
density at its max, water molecules start to occupy less volume what starts to happen?
below 4°C, water begins to expand as it freezes (creating more hydrogen bonds), which is why ice is less dense than liquid water.
- creates space between water molecules as it cools/starts freezing
density of ice
0.917g/cm3
density of salinity water
1.028g/cm3
(salt increases the density of water)
Salinity also affects
freezing point and boiling points of water
- freezing point depression
- boiling point elevation
salt water and freezing point depression
when salt is added to water, it lowers the temperature at which the water will freeze.
salt water and Boiling point elevation
the boiling point of seawater is higher than that of pure water
the presence of dissolved solids (salt) in water
reduces the latent heat of fusion (the energy needed to melt ice) and vaporization (the energy needed to boil water)
salt water lowers latent heat
decrease is about 4%
- The dissolved salts make it easier for the water molecules to change phases because they disrupt the hydrogen bonding between water molecules, meaning less energy is needed for phase transitions
What is salinity?
- Total amount of solid material dissolved in water, including dissolved gasses
- Averages 3.5% ; usually give as parts per thousand (per mil) – e.g., 35‰
one kilogram of seawater what makes it up
965.6g of water
34.4 grams of other components (salinity)
what represents 99% of all dissolved soilds
7 ions (Cl and Na dominate)
and 90 other elements
what are the most abundant ions producing salinity
chloride - 18.980g
sodium- 10.556g
what makes up the salinity of water (list the ions)
- chloride
- sodium
- sulfate
- magnesium
- bicarbonate
- calcium
- potassium
- other
what can change salinity?
Addition or removal of water (not changing amount of dissolved solids)
water cycle effects on ocean salinity
decrease salinity–> precipitation of rain or snow, river runoff, groundwater flow to ocean, melting of ice
increase salinity–>freezing of seawater (salt remains in the water not the ice), evaporation of seawater (salt doesn’t evaporate)
where are the ions in the salinity coming from?
- river discharge
- volcano
- atmospheric deposition
- hydrothermal activity (chemical reactions at the mid- ocean ridge both add and remove various dissolved components)
- biological processes
river discharge puts what into ocean
- carbonate
- calcium
- sulfate
- sodium
volcano puts what into water?
- chloride
- sulfate
(sulfur)
mid-ocean ridge what is added or removed from oceans
added: calcium and potassium
removed: magnesium and sulfate
how are ions (dissolved components removed)
by adsorption, precipitation, ion entrapment in sea spray, and marine organism that produce shells or skeletons
what bring the greatest amount of dissolved solids to ocean?
rivers
look at composition of seawater vs river water
slide 37 lecture 3
salinity of seawater
35%
salinity of river water
0.12%
why discrepancy with seawater and river water
residence time
Residence time
average length of time that an ion spends in the ocean
* Times vary depending on how chemically active (reactive) an ion is
what has the longest residence time
chloride (100,000,000 years)
with new material constantly being added to ocean and long residence times of these ions, why arent ocean getting saltier?
removal processes
what are ion removal processes
- adsorption and precipitation
- sea spray
- biological processes
- hydrothermal activity at the mid ocean ridge
Salinity varies in the ocean
- Evaporation enriches dissolved solutes
- Precipitation dilutes dissolved solutes
how can you measure salinity
- salinometer
- principle of constant proportions
salinometer
measures the electrical conductivity of seawater
principle of constant proportions
ratio of dissolved solids in the ocean is constant across different location in the ocean
who established principle of constant proportions
William Dittmar
principle of constant proportions; Based on the assumption
Ratios of major dissolved salts at Site 1 = Ratio of major dissolved salts at Site 2
- Different salinities but proportions of major salts remains the same
- measure concentration of one major dissolved solid- determine salinity (typically Cl by weight in water sample)
Salinity (‰) =
1.80655 x chlorinity (‰
remote sensing to measure sea surface salinity example
- Aquarius instrument, aboard satellite (2011-2015)
remote sensing Uses
microwave radiometer
microwave radiometer
- Salinity affects electroconductivity, which in turn alter microwave
radiation released from the oceans - Interference from ocean roughness (waves)
- Satellite also included radar scatterometer
- is indirect method (measuring microwave waves which gives info about the salt)
Salinity (and density) also vary by
depth
what does salinity changes in depth result in
layered ocean
- 2 water masses of differing densities are present
example of layer ocean (what is the layers)
- fresh water
- hydrogen sulfide
- salt water (deepest because it is most dense)
refer to image on slide 45 lecture 3
density increase with
depth
what are the 3 zones of water masses
- surface zone
- pycnocline
- deep zone
surface zone
freshwater (2% of ocean water)
pycnocline
- layer of rapidly changing density
- low density to higher density (18% of ocean water)
deep zone
- high density (80% of ocean water)
what helps make these 3 zones?
temperature (cold) (until 4 degrees because remember it becomes less dense after is cools more that 4 degrees/freezing)
pycnocline at low latitudes
very pronounced because of the large difference in temperature between the warm surface waters and the much colder deeper waters
pycnocline at high latitudes
(near the poles), there is little to no pycnocline because the temperature of surface water is already close to the temperature of deep water.
- Since the temperature doesn’t change much with depth in these regions, there is no rapid density change.
Halocline
layer of rapidly changing salinity with depth
the salinity curve for high latitudes (halocline)
shows decreased salinity at the surface and increased salinity at depth
the salinity curve for mid-latitudes (halocline)
shows increased salinity and decreased salinity at depth
what explains the mirrored shapes of these salinity profiles at high and low latitudes?
high (and equatorial) latitudes: precipitation more than evaporation
low to mid latitudes: evaporation more than preciptiation
thermocline
layer in the ocean where the temperature changes rapidly with depth.
what affects the thermocline
- Seasonality
- Location on Earth
- Influence on density (colder water sinks, warmer water rises)
mid-latitudes thermocline
permanent
- turnover change between seasons
- Near the equator (low latitudes), water is consistently warm, and the thermocline is typically more pronounced
high latitudes (near the poles), thermocline
the temperature difference between surface and deep waters is less pronounced, and the thermocline is absent because the surface and deep waters are all cold
Earth’s ocean and atmosphere are intimately intertwined
Air and ocean act as one inter
dependent system
what are major driver of ocean circulation
winds
Massive amounts of ___ and ____ exchanged between oceans and
atmosphere
energy and matter
Key features of weather and climate driven by
ocean-air interactions
Latitude and solar radiation
- Unequal intensity of solar irradiation (insolation)
caused by curvature of the Earth’s surface - Less insolation per area (W/m2) with ↑ latitude
At the equator; sunlight
hits the Earth at a direct, vertical angle (high angle of incidence), concentrating the energy over a smaller surface area. This means the area receives more solar radiation
- less atmospheric absorption
- lower albedo
At higher latitudes (closer to the poles), sunlight
hits the Earth at a slanted angle (low angle of incidence). This spreads the sunlight over a larger area, reducing the intensity of radiation received per square meter
- more atmospheric absorption
- higher albedo (reflection)
Latitude and solar radiation – balanced out via circulation
refer to page 57 lecture 3
The Southern Hemisphere has
greater proportion of ocean (81%) compared to the Northern Hemisphere (61%).
because there is more oceans in southern hemisphere and oceans absorb heat, you think they warmer right? NO. why?
Antarctica (located in south pole) is very cold → circumpolar vortex = less south to north energy transfer
- reflects solar radiation due to its high albedo
Characteristics of the atmosphere; Composition (of dry air)
dominated by N and O
troposphere
heated from below, temperature decreases as you move higher in troposphere
- where all weather is generated
in the stratosphere
atmospheric temperature generally increases with increasing altitude
- because reacting (with ozone) in here it is absorbing heat
ozone layer
protects earth from harmful radiation
for review of the atmosphere and temperature
refer to slide 59 lecture 3
cold air
- slow moving
- less contact
- less recreations
- more dense
- hold less water vapor
hot air
- fast moving
- more contact
- more reactions
- less dense
- holds more water vapor
atmospheric density varies which creates
a convections cell
convection cell
hot radiator –> hot air rises–> cold window—> cools air and causes it to fall
Manifestation
Precipitation (i.e., orographic precipitation, convective storms)
Interrelationship of temperature, density/pressure, and relative humidity
example of relationships on image slide 61 lecture 3
Change atmospheric pressure
air moves due to changes in molecular density
Adiabatic
A process that occurs without heat exchange with surroundings
Warm surface air
low pressure zones, air rises, expands
Cool upper troposphere air
sinks & compresses, creating surface high pressure zone
a column of cool dense air causes
high pressure at earths surface, which leads to sinking air and molecule close together
(wind moves air from high pressure to low pressure)
a column of warm less dense air causes
low pressure at earth’s surface which leads to rising air and molecules far apart
(wind moves air from high pressure to low pressure) thats why the warm air is rising
rising air cools due to
expansion
sinking air warms due to
compression (work)
