Transcript Integrating Chemistry into SCI 210 The Dynamic earth

Integrating Chemistry into SCI
210 The Dynamic Earth
Andrea Koziol, Dept. of Geology
Chemistry in Earth science
• Chemical concepts
actually quite
pervasive
• Touched on in lecture
in a number of
instances
Emphasized in these areas
• Minerals
• Energy and mineral resources
• Greenhouse effect (action of CO2
molecule)
• Chemical weathering
• H2O changes of state, latent heat (clouds
and weather)
• Ozone in the stratosphere
• Numerical dating with radioactive isotopes
Crystalline nature
• Orderly internal arrangement of atoms in
a lattice
• A specific pattern that repeats at regular
intervals
minerals
Oil and gas
• Oil and gas are hydrocarbons: chains or
rings of C and H
• React with O2 to form gas and heat energy
• For example:
• 2 C8H18 + 25 O2 = 16 CO2 + 18 H2O +
heat energy
Natural resources
This is the Greenhouse Effect
• Water and CO2
molecules
absorb this heat
energy
• The atmosphere
is heated from
the ground up
• This heat stays
in the
atmosphere
H2O
Greenhouse effect I
Infrared
CO2
Chemical Weathering
• Chemical weathering: destruction or
altering of minerals when rock comes in
contact with water solutions or air.
• Examples:
• Dissolution by water or carbonic acid,
oxidation, reaction to new minerals
weathering
Chemical weathering examples
• Dissolution by carbonic acid: CO2
dissolves in H2O (rain) to form weak
carbonic acid (H2CO3) which attacks
limestone, marble
weathering
Atmosphere II
Moisture and Clouds
• It’s about H2O and changes in state:
• Ice --- liquid --- water vapor
Latent heat (hidden heat)
• Latent heat: heat added that is not
associated with temperature changes. It is
energy absorbed or released during a
change in state.
• Storing this latent heat, moving it around,
is important!
Atmosphere II
Global: CO2, Greenhouse
Effect, Global Warming
• Today: CO2 concentration in our
atmosphere is >0.036 % or 360 PPM
• If less CO2: cooler temperatures and
cooler climate
• If more CO2: warmer temperatures and
warmer climate
Global climate change
Global climate change
Most up-to-date info
What is ozone?
• Oxygen molecule: O2
• Ozone molecule: O3
• Very little ozone in troposphere
– What is there is a pollutant
• 90% of ozone is in the stratosphere
Ozone
How this works, cont’d.
• O3 + UV light energy = O2
+ O (UV light totally
absorbed)
• O2 + O recombine rather
quickly
• Reaction repeats
• UV light from Sun
almost totally absorbed
Ozone
Parents and daughters
• Starting radioactive isotope: parent
• After decay, it’s different: daughter
• The number of protons, neutrons have
changed by radioactive decay
• Example: carbon-14 (6 protons, 8
neutrons) decays to nitrogen-14 (7
protons, 7 neutrons)
Numerical dating
Rate of decay
• How a parent atom decays, and rate of
decay is fixed.
• Rate of decay doesn’t vary, no matter
what physical or chemical conditions
the isotope is in.
• Every parent atom produces one kind of
daughter
• So: look at amount of parent left,
amount of daughter present.
Numerical dating
Now: radioactivity
• Radioactive
decay is not
linear.
• It is
exponential.
(see fig.10.14,
decrease in # of
parent isotopes
as time passes)
Numerical dating
Radioactive decay example
• Start with 160 parent atoms in our sample. How
much time has passed?
• T = 0 half-l.
160 parents
0 dau.
• T = 1 half-l.
80 parents
80 dau.
• T = 2 half-l.
40 parents
120 dau.
• T = 3 half-l.
20 parents
140 dau.
• Look at ratio of parents to daughters to tell time.
Numerical dating