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– ionic bonds form by attraction between

particles with opposite charges

Water

• H2O

• covalent bonds hold the 2 hydrogen & 1 oxygen together

Water

• Water molecules have an uneven distribution of charge = polar– H positive– O negative

Water

• Polar nature of water leads to:– attraction of other water molecules– attraction of other charged or polar molecules

Water

• Hydrogen Bonds– form between hydrogen of one water molecule

and the oxygen of another– cohesion

cohesion

Water spider

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3 “states” of Water

• Solid

• Liquid

• Gas

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

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

Water

• Universal solvent

• Solution– solvent – solute

Seawater

• 96.5% water & 3.5% solutes

• solutes change properties of water

Seawater

• 96.5% water and 3.5% solutes

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

Seawater

• Salinity– total concentration of all dissolved inorganic

solids

– average = 3.5% or 35 ppt (35o/oo)

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

• 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

• The hydrologic cycle describes the exchange of water between ocean, land and atmosphere.– On land precipitation exceeds evaporation.– In the ocean evaporation exceeds precipitation.

Recycling of Water

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

• 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 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

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

• Depends on temperature and salinity

• density increases as temperature decreases

• density increases as salinity increases

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).

Fig 6-19, p.136

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

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

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.

• 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• 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 Ocean

• 3. the deep zone– a cold (1 to 3oC), dense layer on the bottom

– most of the ocean (80%)

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

– pycnocline

– deep layer

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Contrasting features of shallow and deep ocean water

Thermocline, Halocline, and Pycnocline

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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

• 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

Slide 52

Slide 53

“regular” ocean light penetration – blue dominates

Slide 54

strobe light penetration – blue HUES (+ other colors) dominate

SOUND

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

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

sofar layer, in which sound waves travel at minimum speed

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?

• 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.

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

• In turbid coastal waters light rarely penetrates deeper than 20m.– The water appears

yellow to green because particles reflect these wavelengths.

Fnft: Yangtze River

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