Basic chemistry

○
Atomic structure
 Nucleus = protons (positive) + neutrons
(neutral)
http://www.rstp.uwaterloo.ca/manual/matter/graphic/atom.jpg

Electrons (negative charge)
 Found in shells around nucleus
 1st shell can hold 2 electrons; 2nd and

3rd shells can hold 8 electrons
 Not all atoms have shells that are
completely filled
Atoms bond with other atoms to fill
outer shell

Chemical bonds


Attractive force that holds atoms together
Three major types
○ Ionic bonds
○ Covalent bonds
○ Hydrogen bonds
http://serc.carleton.edu/images/usingdata/nasaimages
○ Ionic bonds – weak bonds
 Atoms “exchange” electrons  fill outer shell
-  becomes positive ion if lose electron
-  becomes negative ion if gain electron
- + & – ions attracted to each other
 Na & Cl  Na+ + Cl-
http://www.physicalgeography.ne
t/fundamentals/images
http://www.msnucleus.org/member
ship/html/k-6/rc/minerals/3
Covalent bonds – strong bonds




Atoms “share” electrons to fill outer shell
H (hydrogen) has one electron, needs 1 more
O (oxygen) has 6 electrons in outer shell, needs two
electrons


Therefore, oxygen and 2 hydrogens bond to form water
Covalent bonds are stronger because there is sharing of
the electrons
http://www.theochem.ruhr-unibochum.de/~axel.kohlmeyer/cpmd-vmd
http://ghs.gresham.k12.or.us/science/ps/sci/ib
bio/chem/notes/chpt2

Polarity of covalent bonds
Nonpolar covalent – electrons are shared equally
○ Polar covalent - electrons not equally distributed
in molecule
○
○
Water is a dipolar molecule (two polar covalent bonds)
 O strongly attracts electrons  slightly
negative
 H slightly positive
-
○
Think of oxygen as being the “bully” – it’s larger so it pulls the
electrons towards it’s nucleus more often
Allows formation of H-bonding between water molecules
H2O molecule
One hydrogen H and two oxygen O atoms
bonded by sharing electrons
 Both H atoms on same side of O atom
 Dipolar covalent bond

Hydrogen bonding

Polarity 
 small negative charge at
O end
 small positive charge at
H end
 Attraction between + and
– ends of water molecules
to each other or other
ions
 Happens because of the
polar covalent bond
Fig. 5.3
Hydrogen bonding and water

Hydrogen bonds are
weaker than covalent
bonds but still strong
enough to result in unique
properties of water
http://faculty.uca.edu/~benw/biol1400
 Cohesion = sticks to other
water molecules
 Adhesion = sticks to other
types of molecules
 High surface tension
http://ucsu.colorado.edu/~meiercl/photography
Hydrogen bonding and water
 H-bonds absorb red light,




reflect blue light  blue
color
High solubility of
chemical compounds in
water
Solid, liquid, gas at
Earth’s surface
Unusual thermal
properties
Unusual density
http://www.pacific-promotion.com.fr/Phototek
Unusual thermal properties of H2O
H2O has high boiling
point
 H2O has high freezing
point


Most H2O is in liquid
form of water on
Earth’s surface
 VERY important for life
http://www.magnet.fsu.edu/education/tutorials/magnetacademy/s
uperconductivity101/images/superconductivity-temperature.jpg
Fig. 5.6
Unusual thermal properties of H2O

Water high heat capacity (specific heat)
 Amount of heat required to raise temperature
of 1 gram of any substance 1o C
 Water can take in/lose lots of heat without
changing temperature – must break H-bonds
 On the other hand, rocks have low heat
capacity
○ Rocks quickly change temperature as they
gain/lose heat
Global thermostatic effects

Moderates temperature on Earth’s surface
– water temp less variable and less extreme
than air temperatures
 Equatorial oceans (hot) don’t boil
 Polar oceans (cold) don’t freeze solid
Global thermostatic effects

Marine effect
 Oceans moderate temperature changes day/night; different
seasons

Continental effect
 Land areas have greater range of temperatures day/night
and during different seasons
 Look at the differences between coastal Florida compared
to Orlando
Density of water
Density of water
increases as
temperature decreases
down to 4oC
 From 4oC to 0oC
density of water
decreases as
temperature decreases
 Density of ice is less
than density of water

http://www.grow.arizona.edu/img/water
Density of water
Fig. 5.10
Density of water

Dissolved solids reduce
freezing point of water
 As water freezes, the
crystalline structure
“pushes out” much of the
dissolved solids
 Creates icy “slush” and
surrounding waters become
saltier
 Putting salt on icy roads
melts ice
○ Salt lowers freezing point
of water on roads allowing
it to remain liquid at colder
temps
http://www.ibarron.net/users/robert/pics/2003/Norway/OsloFjord11.jpg
Water = Life
•
Summary:
• Unique properties of water that make life possible
• High heat capacity and specific heat
• Moderates climates
• Keeps equatorial regions from boiling and pole regions from
freezing solid
• High latent heat – when undergoing change of state, large
amount of heat is absorbed or released
• Sweat evaporating from your skin draws heat from your
body, keep you cool
• Ice is less dense than liquid water
• Cohesion
• Water moving up xylem in plants
• Surface tension – allows plankton to stay near surface of
water
Salinity



Six elements make up 99%
of dissolved solids in
seawater – from erosion of
land, volcanism
Total amount of solid
material dissolved in waterTraditional definition
Typical salinity is 3.5% or
35o/oo


o/oo
or parts per thousand (ppt) =
grams of salt per kilogram of water
(g/Kg )
Adding salts changes
many properties of
water
Fig. 5.12
Pure water vs. seawater
Salinity variations
Open ocean salinity 33 to 38 o/oo
 However, coastal areas salinity varies more
widely

 Influx of freshwater lowers salinity or creates
brackish conditions
 Greater rate of evaporation raises salinity or
creates hypersaline conditions
 Salinity may vary with seasons (dry/rain)
Deep ocean variation of salinity

Surface ocean salinity is
variable
○ Due to occurrences at
surface – rain,
evaporation, etc
Deeper ocean salinity is
nearly the same (polar
source regions for
deeper ocean water)
 Halocline, rapid change
of salinity with depth

pH – Acidity and alkalinity
Acid releases H+ when
dissolved in water (HCl,
H2SO4)
 Alkaline (or base) releases OH(NaOH)
 pH scale measures the
hydrogen ion concentration

 Low pH value, acid
 High pH value, alkaline (basic)
 pH 7 = neutral
http://www3.oes.edu/ms/science6/Pictures%20of%20Science%20Concepts/pH%20Scale.gif
Figure 5.17

Oceans absorb carbon dioxide from the atmosphere
○ How do humans put excess CO2 in atmosphere?


CO2 reacts with seawater to form carbonic acid
 Releases H+ , decreasing pH
The additional H+ bind to carbonate ions to form
bicarbonate
○ Less carbonate in the water makes it difficult for corals, mollusks,
echinoderms, calcareous algae, etc. to form calcium carbonate
Ocean Acidification

Ocean water is basic – pH ~8.1
○ Surface waters have already absorbed enough
CO2 to experience a pH decrease of 0.1 since
pre-industrial times
- May not seem like a lot but remember that pH is
measured on a logarithmic scale so that represents a
30% drop in a relatively short time period
Density of seawater
1.022 to 1.030 g/cm3 surface seawater
 Saltwater more dense than pure water

 That is why you can float better in saltwater
Ocean layered according to density
 Density seawater controlled by temperature,
salinity, and pressure

 Most important influence is temperature
 Density increases with decreasing temperature
Density of seawater


Overall, temp has greatest effect
on density
However, salinity greatest
influence on density in polar
oceans
 polar ocean is isothermal (same
temperature as depth
increases)
 Currents from lower latitudes
bring higher salinity water into
polar areas
 But polar waters are overall
isothermal AND isopycnal
http://www.waterencyclopedia.com/images/wsci_03_img0394.jpg
Density versus depth
Pycnocline, abrupt change of density with
depth
 Thermocline, abrupt change of temperature
with depth
 Density differences cause a layered ocean

 Mixed surface water
 Pycnocline and thermocline
 Deep water
Misconceptions
Increases in global temperatures in the
atmosphere and the consequent warming
of the oceans will only create a problem
for people living along the coast.
 Water exists in the ground in actual rivers
or lakes that are constantly renewed.
 People drink bottle water because it is
better for our health; the safety of tap
water is below consumption standards.

Ocean Literacy Principles



1e - Most of Earth’s water (97%) is in the ocean. Seawater has unique properties: it is saline, its
freezing point is slightly lower than fresh water, its density is slightly higher, its electrical conductivity is
much higher, and it is slightly basic. The salt in seawater comes from eroding land, volcanic
emissions, reactions at the seafloor, and atmospheric deposition.
1g - The ocean is connected to major lakes, watersheds and waterways because all major
watersheds on Earth drain to the ocean. Rivers and streams transport nutrients, salts, sediments and
pollutants from watersheds to estuaries and to the ocean.
3a - The ocean controls weather and climate by dominating the Earth’s energy, water and carbon
systems.
Sunshine State Standards









SC.6.E.7.1
Differentiate among radiation, conduction, and convection, the three mechanisms
by which heat is transferred through Earth's system.
SC.6.E.7.6
Differentiate between weather and climate.
SC.8.P.8.1
Explore the scientific theory of atoms (also known as atomic theory) by using
models to explain the motion of particles in solids, liquids, and gases.
SC.8.P.8.4
Classify and compare substances on the basis of characteristic physical
properties that can be demonstrated or measured; for example, density, thermal or electrical
conductivity, solubility, magnetic properties, melting and boiling points, and know that these properties
are independent of the amount of the sample.
SC.8.P.8.6
Recognize that elements are grouped in the periodic table according to
similarities of their properties.
SC.8.P.8.8
Identify basic examples of and compare and classify the properties of
compounds, including acids, bases, and salts.
SC.912.E.7.9
Cite evidence that the ocean has had a significant influence on climate change
by absorbing, storing, and moving heat, carbon, and water.
SC.912.P.8.4
Explore the scientific theory of atoms (also known as atomic theory) by
describing the structure of atoms in terms of protons, neutrons and electrons, and differentiate among
these particles in terms of their mass, electrical charges and locations within the atom
SC.912.P.8.5
Relate properties of atoms and their position in the periodic table to the
arrangement of their electrons.