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Element= a substance composed of many “identical” particles called atoms.

= the most basic substances that matter can be broken into by chemical means

= the “ingredients” making up everything

Chapter 5 – Water and Seawater

What elements are in water?

hydrogen (H) and oxygen (O)

Information about all known elements is shown in the Periodic Table

Electron (-)

Proton (+)

Neutron

Nucleus

Electron Shells

The Parts

of an Atom

Atom = the smallest piece of an element that retains the properties of that element.

Atoms contain two main parts and three types of subatomic particles

Nucleus

Protons

Neutrons

Electron Shells

Electrons

Figure 5.1, p. 130

Particle Name Where Found Electrical Charge Mass Y/N? Other
Proton Nucleus + Yes Determines Type of element
Neutron Nucleus ø Yes # can change for the same element
Electron Electron Shell - No # can change for the same element

For an atom to be electrically neutral, # electrons = # protons

http://www.vtaide.com/png/atom.htm

Ion = an electrically charged atom.

# of electrons (-) ≠ the # of protons (+)

Negative ions (too many electrons)

Positive ions (too few electrons)

These will be attracted to each other.

Oxygen

O-2

Lithium

Li+1

http://itc.gsw.edu/faculty/speavy/spclass/chemistry/ions.htm

Compound = substance formed when two or more ions bond together.

= different properties than the elements which formed it.

= examples include water (H20) carbon dioxide (CO2) and halite or table salt (NaCl).

Molecule = the smallest piece of a substance that retains the properties of that compound.

Ex. NaCl = recipe for 1 molecule of salt

Bonding = a group of processes that hold molecules together. = molecule “glue”

Wicander and Monroe, @009, Essentials of Geology

A Water Molecule is held together by covalent bonds =

atoms in the molecule share electrons.

2H +1 + O-2 => H20

Garrison, 2012, Essentials of Oceanography

Recipe for 1 molecule of water

Water molecules are electrically neutral, but polarized.

Their angular shape clusters the – charges on one side, and the + charges on the other side.

Opposites still attract, so…

http://www.free-extras.com/images/mickey_mouse-1101.htm

A water molecule looks like Mickey Mouse, so they are electrically polarized.

Fig.5.3, p. 131

Hydrogen bonds => The + end of one water molecule sticks to the – end of the next water molecule.

http://www.qualityuswater.com/weregreen.htm

Water has some special properties due to its polarized nature:

Cohesion = water sticks to itself (hydrogen bonding)

Surface tension = water has a thin “skin” on the surface

can support light objects but they are NOT floating

http://www.britannica.com/EBchecked/topic-art/575080/117360/Aluminum-coin-supported-by-the-surface-tension-of-water

What causes surface tension?

The molecules of a liquid are always trying to pull one another together. In the middle of a liquid, a molecule is pulled equally hard from all directions, so the attractive forces cancel out. But a molecule on the surface is only pulled downward. This downward tug draws the surface of the liquid tightly together, so it appears to have a skin.

http://www.daviddarling.info/childrens_encyclopedia/matter_Chapter3.html

Water has some special properties due to its polarized nature:

Cohesion

Surface tension

Adhesion -> why stuff gets wet

Dissolving ability = The polarized water

molecules can attach to and pull apart the

ions in compounds.

water is the universal solvent.

http://tasblogs.tas.edu.tw/wpmu/oliverf18109631/2010/11/24/33/

http://bioap.wikispaces.com/Ch+3+Collaboration

See also figure 5.4, p. 131

Water Molecules dissolve salt crystals by pulling the sodium and chloride ions apart.

Salt water is not water and salt,

it is water with chloride and sodium ions floating around in it.

Heat = The energy produced by the random vibration of atoms or molecules -> depends on the rate of vibration and the number of particles (mass).

Heat is stored energy

Heat is measured in calories

http://hop.concord.org/h1/phys/h1p.html

Temperature => measures only the rate of vibration and not how many particles are vibrating.

Higher the temperature => faster vibration.

measured in degrees.

In the U.S. we use Fahrenheit degrees (°F)

In the metric system, we use Celsius degrees (°C)

Scale Freezing point Boiling point conversion
Fahrenheit 32 °F 212 °F F-32° X 5/9
Celsius 0 °C 100 °C C X 9/5 + 32°

Density = mass per volume = mass/volume. Density is a measure of how “heavy” something is.

Density is measured in grams per cubic centimeter = g/cm3

Which is more dense? Why?

http://www.dimensionsguide.com/brick-sizes/

http://southernartistictouch.blogspot.com/2010/03/italian-bread-bread-machine.html

The three states of matter:

Solid – atoms or molecules are “frozen” into a rigid structure where they vibrate. Solids maintain their shape and size. Water molecules experience hydrogen bonding.

Liquid – atoms or molecules have more energy and are moving randomly. Liquids maintain their size but will change flow to fill the bottom of their container. Water molecules still experience hydrogen bonds, but they break and reform.

Gases – atoms or molecules have so much energy they move rapidly past each other. Gases expand to fill their container. Water molecules no longer experience hydrogen bonding.

Specific Heat Capacity = the amount of heat required to raise the temperature of 1 gram of a substance by 1 °C.

Measured in cal/gm/°C or calories per gram per degree Celsius

Latent Heat = the amount of heat required to change an object’s phase (added to melt, removed to freeze) . Note that there is no change in temperature as the phase changes.

Measured in cal/gm or calories per gram.

Salt = inorganic solids dissolved in water –

these are not just table salt…

Salinity = the % of water, by weight, that is dissolved inorganic solids (salts)

=> salinity is measured in parts per thousand ‰

1 ‰ = 0.1%

=> average ocean salinity is 35 ‰ = 3.5%

This means that if I evaporated 1000 cups of seawater I would get 35 cups of salt!

http://article.wn.com/view/2010/11/22/Drilling_the_Dead_Sea_for_history/

Some definitions you should know:

Solution = a homogeneous substance made of two components: a solvent and a solute.

An example is saltwater.

Solvent = the dissolver.

Water is a great solvent.

Solute = what dissolves.

Salt is a solute.

Saturated Solution = holds as much solute as it can for the given temperature and pressure conditions.

Colligative Properties of Salt Water (properties of a solution)

Specific Heat Capacity (heat needed to raise the temperature) decreases as salinity goes up

(the saltier the water is, the faster it heats up)

Freezing point decreases as salinity goes up

(salty water has to get colder to freeze)

Salty water evaporates more slowly than

fresh water

because the dissolved ions attract

the water molecules.

http://offthemark.com/search-results/key/truck/

http://dailydogrel.wordpress.com/2011/01/07/puddle-huddle/

Salts enter the oceans:

1) Rivers which carry dissolved rocks (why water tastes)

2) Volcanic eruptions (outgassing again)

3) Hydrothermal vents (dissolving rocks of the oceanic crust)

4) Dissolution of sediments on the seafloor

Salts exit the ocean:

1) Sea spray deposits salts on shore (hydrogenous sediment)

2) Biologic activity – nutrients for life (biogenous sediment)

3) Adsorption – sticking to other sediments as they sink

4) Hydrogenous sediments of the deep sea floor

Evidence suggests that the average salinity of the oceans has been stable for 1.5 BY, so

Salts in = salts out

The Ocean is in Chemical Equilibrium

http://article.wn.com/view/2010/11/22/Drilling_the_Dead_Sea_for_history/

http://fishes.southernfriedscience.com/?tag=tube-worms

Chemical Makeup of Average Seawater: water = 96.6% (by weight) major constituents = 3.4% minor constituents <0.01%

The major or conservative constituents of seawater.

99.99% of all salts in the ocean.

The most abundant ions in seawater:

Chloride (Cl-),

Sodium (Na+),

Sulfate (SO42-),

Magnesium (Mg2+),

Calcium (Ca2+),

Potassium (K+), and

Bicarbonate (HCO3-).

All IONS because they have been dissolved (taken apart) by the water!

The Principle of Constant Proportions states: Although the total salinity (amount of the major ions) varies from place to place, the ratio of one ion to the others remains fixed (except near the coast).

If I have 100 pennies and 15 nickels, the ratio will be 100 to 15, no matter if I throw them in a cup of water or a pool of water, right?

Minor and Trace Elements

0.01% of total salinity

non-conservative as their amount varies with location and season..

do not follow the principle of constant proportions!

Garrison, 2010, Oceanography, In Introduction to Marine Science

Residence Time = the average time a substance remains in solution, in this case, remains dissolved in the ocean.

= Amount of the element in the ocean

Rate at which the element is added or removed

Major

Minor

The major or conservative elements have long residence times. For example, Chlorine ions remain in the ocean an average of 100,000,000 years.

Remember the Principal of Constant Proportions?

The major ions always occur in the same ratio to each other regardless of salinity values.

This occurs because the ocean is well stirred by the action of winds, waves, and current.

The only place the principal of constant proportions does not hold true is near the coast.

WHY?

Because new salts are

constantly added by rivers

and haven’t had time to

get stirred in.

Residence Time = the average time a substance remains in solution, in this case, remains dissolved in the ocean.

The Principle of Constant Proportions states: Although the total salinity (amount of the major ions) varies from place to place, the ratio of one ion to the others remains fixed (except near the coast).

The Major or Conservative Ions have EXTREMELY long residence times, and obey the Principal of Constant Proportions. They have been well stirred into the ocean.

The Minor and Trace Ions have short residence times, and do not occur in constant proportions to each other. They are used In short term biological and geologic reactions.

Concept Review-

Gases also dissolve in seawater – good thing or nothing could live in the ocean!

1) most abundant are nitrogen, oxygen, and carbon dioxide.

2) dissolve into the water at the surface,

3) released during biologic processes

4) Nitrogen is used by organisms to create proteins 5) Carbon dioxide and oxygen concentrations are linked by photosynthesis and respiration

Photosynthesis (“plants”) uses CO2 to store the sun’s energy as food, and releases O2 as a waste product.

6H20 + 6CO2 + sun + nutrients => C6H1206 + 6O2

Respiration (“animals”) uses O2 to break down food to retrieve energy, and releases CO2 as a waste product.

C6H1206 + 6O2 => 6H20 + 6CO2 + energy

pH is a measure of how acidic or basic a solution is.

Pure water is neutral (neither acid or basic) and has a pH of 7.

Acids have pH values less than 7, the lower the pH, the more acidic the substance is – think lemon juice!

Bases have pH values greater than 7, the higher the pH, the more basic the substance is – think ammonia!

Average

Seawater pH = 8

Like Fig. 5.20, p. 148

At depth, higher concentrations of carbon dioxide lowers pH to 7.5 in middle depths, and 7.0 at the deep sea floor.

So what???????????????

Remember the CCD… the calcium carbonate compensation depth?

This slight increase in the acidity of the deepest ocean water creates the CCD, dissolves calcium carbonate (shells and bones) and restricting shelled life.

Water has SOme very important properties that make it great at climate control!

Water becomes less dense right as it begins to freeze

the internal angle widens

molecules bond together in a crystal lattice structure

SO ICE FLOATS

http://www.physicalgeography.net/fundamentals/8a.html

Note – this graph represents the behavior of pure water, not seawater!

Water has one of the highest specific heat capacity and latent heats of any common substance. =>extra energy needed to break the hydrogen bonds holding water together.

Heat Capacity of liquid water = 1 cal/gm/°C

Granite / rock = 0.2 cal/gm/°C

Alcohol = 0.3 cal/gm/°C

Ice = 0.5 cal/gm/°C

Steam = .47 cal/gm/°C

raising the temperature of water even a little bit stores a lot of heat, while cooling water releases a lot of heat.

3) Water also has some of the highest latent heats of any common substance. =>extra energy needed to break the hydrogen bonds holding water together.

a. Latent heat of melting = latent heat of freezing = heat that must be added to melt a solid, or removed to freeze a liquid (with no change in temperature)

The latent heat of fusion for water = 80 cal/gm

b. Latent heat of vaporization = latent heat of condensation = the heat that must be added to evaporate a liquid at 100° or removed to condense as gas at 100° (with no change in temperature)

The latent heat of vaporization for water = 540 cal/gm

c. Latent heat of evaporation = heat required to evaporate water at less than 100° (varies with water temperature)

Process Heat required/released Name of constant
Heating/cooling water 1 cal/gm/°C Heat capacity
Freezing/thawing 80 cal/gm Latent heat of fusion
Evaporating/condensing 540 cal/gm Latent heat of evaporation
Heating/cooling of ice and steam ≈ 0.5 cal/gm/°C Heat capacity

Note – the temperature does not change until all ice turns to water (or all water turns to ice)

Note – the temperature does not change until all water turns to steam (or all steam turns to water)

The calories we count are 1000 of these calories!

The heat energy that is added as things warm up has to be removed again as they cool down.

Water’s high heat capacity and latent heats , along with the fact that ice floats, allows our oceans to moderate our daily, seasonal, and tropics to poles temperature changes.

When it is hot the water warms and stores heat cooling the air (day / summer / in the tropics),

When it is cold the water cools and releases the stored heat warming the air (night / winter / at the poles)

at the poles, ice melts, storing heat and cooling the air ( summer or day)

the ice reforms, releasing heat and warming the air (night or winter)

Less temperature variation means weaker storms, smaller waves, and slower ocean currents.

36

What three factors control the density of seawater?

Temperature

Salinity

Pressure

http://www.phawker.com/page/407/

http://www.o-digital.com/wholesale-products/2179/2187-6/UHF-Male-Connector-73928.html

http://chestofbooks.com/crafts/popular-mechanics/Practical-Mechanics-for-Boys/Chapter-I-On-Tools-Generally.html

Effect of Temperature on water density:

As temperature goes up, water density goes down

As temperature goes down, water density goes up (except as water freezes)

Remember, this is for pure water! Salty seawater freezes at a lower temperature (about -2 ° C).

Fig. 6-12, p. 165

Seawater Surface Temperatures

warmer colors = warmer temperatures.

http://www.ssec.wisc.edu/data/sst/

This diagram shows the average temperature distribution with depth at 3 mid-ocean latitudes.

Mixed layer – the top layer with nearly constant temperature. (stirred by winds, waves and currents)

Thermocline – the zone of rapid temperature change

Deep layer – the uniformly cold water below the thermocline.

When we dissolve “stuff” in water, we add mass (“weight”) without changing the volume.

Since density = mass/volume, density goes up as salinity goes up!

But temperature also has an effect – this graph assumes a constant temperature!

What natural factors can alter the

surface salinity in the ocean?

Evaporation and precipitation work together:

only water evaporates, concentrating the salts in the remaining water and increasing the salinity and density; and

precipitation (rain, snow, and sleet) adds pure water, decreasing the salinity and density.

http://www.hnsa.org/doc/sonar/chap2.htm

What natural factors can alter the

surface salinity in the ocean?

Evaporation and precipitation

Freezing and thawing of sea ice:

Only water freezes, concentrating salts in the remaining water and increasing salinity and density; and

Ice melting adds pure water, decreasing the salinity and density.

Seasonal variation in salinity near the poles, more salty in winter, less salty in summer

Melting of ice onland decreases salinity as well.

Remember, the higher the salinity, the denser the water, so the highest salinities are found at the deepest depths. Data from the east coast of Canada.

Mixed layer = top zone of uniform salinity

Halocline = zone of rapid change of salinity

Deep zone = deep layer of nearly constant salinity.

Melting Ice

Evaporation

Water is incompressible - it cannot be squeezed into a smaller volume. So despite pressures of up to 7350 lb/in2 at the seafloor, pressure has a negligible effect on water density!

Garrison, 2009, Oceanography

Salinity and temperature work together to control the density of water. There are many combinations of salinity and temperature that can give the same water density.

The thermocline creates a pycnocline!

The halocline creates a pycnocline!

So, the ocean has layers due to changes in density. This density stratification is due to differences in temperature and salinity.

A water mass is a layer of water with nearly uniform density due to its combination of temperature and salinity.

Water masses acquire their density at the surface due to conditions there (temperature, evaporation, precipitation, etc). Water masses sink to their equilibrium depth once formed.

Note that the density stratification breaks down at the poles, due to the uniformly cold and salty water found there.

These density layers act like rigid boundaries, and prevent vertical water movement over much of the ocean. No layers = no barriers to vertical water movement at the poles.