General chemistry
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General Chemistry. Element composed of atoms Nucleus protons and neutrons electrons. General Chemistry. Molecule a group of atoms held together by chemical bonds. General Chemistry. Bonds covalent bonds form when electrons are shared. General Chemistry. Bonds

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General Chemistry

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General chemistry

General Chemistry

  • Element

    • composed of atoms

      • Nucleus

        • protons and neutrons

      • electrons


General chemistry1

General Chemistry

  • Molecule

    • a group of atoms held together by chemical bonds


General chemistry2

General Chemistry

  • Bonds

    • covalent bonds form when electrons are shared


General chemistry3

General Chemistry

  • Bonds

    • ionic bonds form by attraction between particles with opposite charges


Water

Water

  • H2O

  • covalent bonds hold the 2 hydrogen & 1 oxygen together


Water1

Water

  • Water molecules have an uneven distribution of charge = polar

    • H positive

    • O negative


Water2

Water

  • Polar nature of water leads to:

    • attraction of other water molecules

    • attraction of other charged or polar molecules


Water3

Water

  • Hydrogen Bonds

    • form between hydrogen of one water molecule and the oxygen of another

    • cohesion


Cohesion

cohesion

Water spider

fnft


3 states of water

3 “states” of Water

  • Solid

  • Liquid

  • Gas

  • (and it can go back and forth between these “states” many times!)


General chemistry

So you can have more than 1 state at a time…and why ice floats!


Water4

Water

  • Universal solvent

  • Solution

    • solvent

    • solute


Seawater

Seawater

  • 96.5% water & 3.5% solutes

  • solutes change properties of water


Seawater1

Seawater

  • 96.5% water and 3.5% solutes

  • The SOLUTES are: 85% Salt (Sodium Chloride) and 15% “other.”


Seawater2

Seawater

  • Salinity

    • total concentration of all dissolved inorganic solids

    • average = 3.5% or 35 ppt (35o/oo)


Seawater3

Seawater

  • Source of ocean’s salts

    • weathering of surface rocks

      • sodium, magnesium, calcium

    • outgassing

      • chlorine, carbon dioxide, sulfur, hydrogen


Water is recycled continually between the ocean and the land

Water is recycled continually between the ocean and the land

  • The reservoirs of water include:

    • Oceans:

      • cover 60% of the northern hemisphere

      • cover 80% of the southern hemisphere

      • contain 97% of Earth’s water

    • Rivers, lakes and glaciers

    • Groundwater

      • contains a larger volume of water than all of the combined water in lakes and rivers


General chemistry

  • The hydrologic cycledescribes the exchange of water between ocean, land and atmosphere.

    • On land precipitation exceeds evaporation.

    • In the ocean evaporation exceeds precipitation.


Recycling of water

Recycling of Water


Heat vs temperature

Heat vs Temperature

  • Heat

    • energy produced by the random vibration of atoms or molecules

  • Temperature

    • an objects response to the input or removal of heat energy


Heat capacity

Heat Capacity

  • the heat required to raise the temperature of 1 gram of a substance by 1oC

  • Heat capacity of water = 1 calorie

    • the highest of all known substances

  • water resists changing temperature when heat is added or removed


Density and temperature

Density and Temperature

  • density of water increases as water is cooled until a maximum of 1 g/cm3 is reached at 4oC

  • the density decreases as freezing takes place

  • ice is less dense than water


General chemistry

Why does ice float – ice is less dense than (liquid) water


Seawater vs pure water

Seawater vs. Pure Water

  • Seawater has a

    • lower heat capacity

    • lower freezing point

  • density increases until freezing point is reached

    • ice is pure water & cold, salty water left behind sinks


Density of water

Density of Water

  • Depends on temperature and salinity

  • density increases as temperature decreases

  • density increases as salinity increases


General chemistry

Temp., Salinity and Density have a complex relationship – you can

have the SAME density at different concentrations of Temp. and salinity.


Density zones in the ocean

Density Zones in the Ocean

  • 1. surface zone or mixed layer

    • temperature and salinity are constant with depth

  • 2. a middle layer where density changes rapidly with depth (because of extreme env. changes) = pycnocline

    • Thermocline: temp. changes rapidly w/ depth

    • Halocline: salinity changes rapidly w/ depth

    • NOTE: These 3 zones can ALL coincide together!

      3. The DEEP ZONE (80% of all ocean water) is the layer below the pycnocline (but little change occurs here).


General chemistry

Fig 6-19, p.136


The surface layer

TheSurface Layer

  • About 100m thick

  • Comprises about 2% of the ocean volume

  • Is the most variable part of the ocean because it is in contact with the atmosphere.

  • Is less dense than the layers below because of its lower salinity or higher temperature.


Sea surface temperatures

Sea Surface Temperatures

  • Insolation and ocean-surface water temperature vary with the season.

  • Ocean temperature is highest in the tropics (25oC) and decreases poleward.


The pycnocline

The Pycnocline

  • Is transitional between the surface and deep layers.

  • Comprises 18% of the ocean basin.

  • In the low latitudes, the pycnocline coincides with the thermocline.

  • In the mid-latitudes it coincides with the halocline.


General chemistry

  • Tropical and subtropical oceans are permanently layered with warm, less dense surface water separated from cold, dense deep water by a thermocline.

    • The thermocline is a layer in which water temperature and density change rapidly.

  • Temperate regions have a seasonal thermocline and polar regions have none.


The deep layer

The Deep Layer

  • Represents 80% of the ocean volume.

  • Water in the deep layer originates at the surface in high latitudes, where it:

    • cools

    • becomes dense

    • sinks to the sea floor

    • flows equatorward across the ocean basin


Density zones in the ocean1

Density Zones in the Ocean

  • 3. the deep zone

    • a cold (1 to 3oC), dense layer on the bottom

    • most of the ocean (80%)


General chemistry

  • The water column in the ocean can be divided into the:

    • surface layer

    • pycnocline

    • deep layer


General chemistry

fnft


General chemistry

fnft


General chemistry

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General chemistry

Contrasting features of shallow and deep ocean water


Thermocline halocline and pycnocline

Thermocline, Halocline, and Pycnocline


General chemistry

fnft


Refraction light and sound

Refraction, Light and Sound

  • Refraction: The “bending” of waves. Light and Sound are a direct result/reaction of these waves.

  • Light and Sound waves travel at DIFFERENT speeds depending upon the medium that they are in.


Light in the ocean

Light in the Ocean

  • Sunlight does NOT penetrate (always) to the “bottom.” This is because of many factors such as turbidity (sediments in the water), depth and the scattering/absorption of light through a water medium.

  • Scattering determines how light is absorbed.

  • Water thus absorbs (and scatters) the light

  • PHOTIC vs. APHOTIC zones


General chemistry

Different wavelengths of light produce different colors. As they are

“absorbed/scattered” in the water the colors reach different depths.

Why buy a RED wetsuit?


General chemistry

“regular” ocean light penetration – blue dominates


General chemistry

strobe light penetration – blue HUES (+ other colors)

dominate


Sound

SOUND

  • Similar to light – sound “waves” travel differently through water.

  • Speed of sound in average seawater (w/ average salinity) is 1500 m/sec.


General chemistry

Relationship between water depth and sound velocity.


General chemistry

sofar layer, in which sound waves travel at minimum speed


General chemistry

A side-scan sonar

image of the SS

Nailsea Meadow

resting on the

seabed at a depth

of 113 meters

(367 feet).


What does this mean to marine life

What does this mean to MARINE LIFE?

  • Light effects WHERE plants and animals can live.

  • Temperature effects WHERE plants and animals can live.

  • Salinity effects WHERE plants and animals can live.

  • Dissolved gases are an important factor too.


General chemistry

Open ocean (clear) vs. coastal (sedimented) waters


General chemistry

  • In turbid coastal waters light rarely penetrates deeper than 20m.

    • The water appears yellow to green because particles reflect these wavelengths.

Fnft: Yangtze River


General chemistry

Photic vs. aphotic zones – light penetration @ diff. depths.


General chemistry

Temperature relationships in different ocean environments


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