Basic chemistry for understanding biology

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CHAPTER 3

• Physical and Chemical Properties of Water

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The properties and biological importance of water

• Life on Earth evolved in the water, and all life
  still depends on water.
• 80 of living organism mass.95 of a jellyfishs
• Almost all the chemical reactions of life take
  place in aqueous solution
• Water formula H2O
• 2 Hydrogen atoms
• 1 Oxygen atom

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Waters atoms

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Properties of Water
Covalent bonding vs. Hydrogen bonding
Covalent Bond
Since Oxygen needs 2 electrons, 2 hydrogens will
bond to Oxygen. Each Hydrogen also needs 1
electron, so together, they all share 2 electrons
or covalent bonds.
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Water H2O

• Water molecules are charged, with the oxygen atom
  being slightly negative, and the hydrogen atoms
  being slightly positive . These opposite charges
  attract each other, forming hydrogen bonds.

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States of Matter Water molecules
Water turns to ice at 0 degrees Celsius, and
vapor at 100 degrees Celsius
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Properties of Water - Density

• Density mass/volume
• Water is unique in that the solid state (ice) is
  less dense than the liquid state, so ice floats
  on water.
• Water molecules get further apart as it freezes,
  causing it to EXPAND The decrease in density
  causes ice to float.
• This allows aquatic ecosystems to exist even in
  sub-zero temperatures.

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Water as a solvent

• Solvent A liquid, solid, or gas that dissolves
  another liquid, solid, or gas called solutes.
• When many salts dissolve in water they ionize
  into positive and negative ions
• ex. NaCl     Na Cl-
• Ions- electrically charged particles, water
  molecules are very attracted to them

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Properties of Water - Cohesion

• Cohesion stick together
• Water molecules "stick together" due to their
  hydrogen bonds
• Surface tension is caused by cohesion

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Salinity

• Six ions compose over 99 of dissolved solids in
  water
• Sodium and Chloride make up 85 of that (explains
  why ocean water tastes salty)
• Salinitytotal amount of salt dissolved in
  seawater
• If 35 grams of salt remain when 1,000 grams of
  seawater evaporates salinity 35 parts per
  thousand (ppt or psu)
• This is the avg of open ocean

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Salinity of ocean water varies

• Inflow from river, evaporation rates, melting of
  ice, precipitation, ocean currents
• SALTIEST Red Sea/Persian Gulf and North Atlantic
  (40ppt)

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Rule of Constant Proportions

• The relative amounts of various ions in seawater
  always stay the same, regardless of its salinity

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Salinity Temperature? Density

• Temperature affect waters density
• As temps ? Density / Temps ? Density
• Salinity affects waters density
• As salinity ? Density / Salinity ?
  Density
• Soooo it gets denser as it gets saltier, colder
  or both

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Buoyancy

• Upward force that keeps things afloat
• Floats ()buoyant, Sinks (-) buoyant, Hovers
  neutral

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• The amount of pressure we experience at sea level
  is one atmosphere (1 atm) or 14.7 psi
  (pounds/square inch)
• In water, pressure increases 1 atm every 10 m of
  depth
• Scuba divers and marine organisms have the weight
  of the water column on them

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http//www.youtube.com/watch?vYU2PSHeFSlA
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Pressure and Density

• Water is incompressible (you cannot decrease its
  volume with added pressure) negligible
• Gases ARE compressible due to Boyles Law
  PVconstant
• If P , then V and vice versa

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• IN GASESmolecules are further apart, more room
  to squeeze together liquids and solids dont
  compress
• Density of air INCREASES when under pressure
• Examples of compressed air (gas)

3,000psi
40psi
65psi
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Scuba diver tank

• Made of thick aluminum
• Rounded edges
• Air is put in tank w/ compressor
• 50 ft3 squeezed in, requires 3,000psi OMG!

1 ft3
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Cartesian Diver

• Things you will need

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• Bring supplies Tomorrow!!
• This will be your chance to make mistakes
• You will need a working, functional cartesian
  diver that I will test out individually

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Same process takes place in fish swim bladder.
Muscles compress/decompress the air in bladder to
control how much it floats
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The Bends

• N gas dissolves into bloodstream at high
  pressures.
• If diver surfaces too quickly to lower pressure,
  the gases come out as bubbles in your tissue
• Extreme pain/tissue damage
• Decompression chamber to dissolve gas into blood
  again, then reduce pressure slowly

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Oxygen Solubility

• Oxygen is MORE soluble (dissolved) into colder
  water
• Plankton? fish more abundant in
  cooler/deeper/nutrient-rich water
• Oxygen is LESS soluble in warmer water
• Plankton? fish less abundant in nutrient-poor
  warm water

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Properties of Water - pH

• Water itself is partly ionized
• H2O    H OH-
• pH Scale 1-14
• Acidic pH 1-6
• Acid release H ions
• Neutral pH 7
• Basic pH 8-14
• Bases accept H ions
• Many biochemical reactions are sensitive to pH

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Transparency

• Allows sunlight to penetrate water to
  photosynthetic organisms
• Affected by material suspended or dissolved in
  water
• Secchi disk

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Ocean Blue

• Water is more transparent to blue light
  wavelength
• Other colors of spectrum get absorbed at shorter
  depths while blue can penetrate further down
• Deep ocean organisms colored red, orange, purple.

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What direction does water go down the toilet when
you flush??
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Coriolis Effect

• Earth is round/rotating. Anything moving over
  surface tends to get deflected
• Winds and ocean currents bend to right in N.
  Hemisphere and left in S. Hemisphere

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In ONE word, what makes wind?

• SUN!!!!!!!!!

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Wind

• Warm air at the equator rises (less dense)
• Adjacent air gets sucked in to replace rising
  air.creating trade winds (come in at angle due
  to Coriolis effect)
• Steadiest winds on earth
• Westerlies and polar easterlies run opposite to
  trade (vary)

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Currents

• Wind hitting water creates surface currents that
  move at 45 angle (due to Coriolis)
• Top layer pushes water below that deflects at
  different angle (Ekman spiral)

EKMAN TRANSPORT
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Gyres

• Currents combine into a huge, circular systems
  called gyres
• Gyres warm the poles, cool the tropics and
  regulate the earths climate

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Three layer water column

• Surface (mixed layer)
• Thermocline layer (Intermediate)
• Deep layer (very cold)

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Overturn

• If the surface water gets cold enough (winter),
  it becomes denser and sinks. This is downwelling.
• Displaces deeper water below, deep water rises
  (upwelling)

Sometimes wind can cause this effect in lakes
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The Great Ocean Conveyor

• Constantly replenishes ocean depths with oxygen
• Regulates Earths climate

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• Waves travel through water they do not take the
  water with them.
• Bob up and down
• As a wave arrives it lifts water particles. These
  travel forward, then down and back so that each
  particle completes a circle.
• Circling movements near the surface set off
  smaller movements below them.

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Tides

• Rise and fall of sea surface
• Caused by gravitational pull of moon and sun and
  centrifugal force from rotation of Earth, moon
  and sun
• Spring tide (surge up like a spring of water)
• Neap tide (tidal range is small)

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