Chapter 3 - The Chemistry of Global Climate Change Flashcards
What do greenhouse gases do?
absorb radiation/trap heat
ex. CO2, H2O, CH4
CO2
on the rise more now than 150 years ago (due to Industrial Revolution), earth’s temp has risen
What is the Greenhouse Effect?
process where gases trap heat –> heat stays and warms the planet
- essential for life, planet would freeze otherwise (but too much = bad “enhanced greenhouse effect”)
- energy return of over 80% –> increases earths temp
What is the history of our earth’s atmosphere in relation to climate?
early atmosphere: 1000x more CO2
bacteria used CO2 to make sugars
How do we know that the earth’s temp has increased?
- core samples from ocean, bacteria remaining tells temp
- magnetic alignment of earth
- “heavy water” composition of ice
- trapped bubbles tells concentration of ice when bubbles formed
- all data seems to agree
Global Warming:
- Theory
- What’s possible…
- Fact
Theory: global warming is cased by an increase of CO2 and CH4 levels
Possible: increases in CO2 and CH4 levels are a result of warming, not a cause
Fact: CO2 and CH4 trap heat and contribute to global warming
–> cause or effect?
Recent evidence of global warming
- atmospheric CO2 is increasing
- global temps are increasing
- -> biggest boom from Industrial Revolution
Other factors to global warming
- orbital changes: temp maxima, major/minor ice ages
- Airborne dust: volcanic activity
- Cloud cover: weather patterns
- Greenhouse gases
What is the outlook for the future?
In the past 100 years: -CO2 conc. has increased 25% -avg temp increased .5-.7 degrees C Current: -doubling the CO2 conc. --> 1.8-6.3 degree F increase
What are examples of greenhouse gases? what are not examples? Why the difference?
Examples: CO2, CH4, N2O, O3, H2O, CFCs
Not examples: O2, N2, Ar
Difference due to shape!
Bonds are made of ______
electrons
neg charge, repel each other
Molecular Shape: Tetrahedral
bonded atoms: 4
lone pairs: 0
Molecular Shape: Bent
bonded atoms: 2
lone pairs: 2 or 0
Molecular Shape: Trigonal Pyrimidal
bonded atoms: 3
lone pairs: 1
Molecular Shape: Trigonal Planar
bonded atoms: 3
lone pairs: 0
Molecular Shape: Linear
bonded atoms: 2
lone pairs: 0
Shape of a molecule determines ______
HOW a molecule can vibrate
Types of light
UVB/UVC –> bonds break
IR –> can’t break bonds (not enough energy), can cause vibration
How do you determine which wavelength?
- can’t look at a molecule and determine wavelength
- bond strength and flexibility, atom masses
What is symmetric stretching?
What is asymmetric stretching?
—-><—-
What are bending modes?
up/down OR diagonal
*need at least three atoms to bend (O2 can’t bend)
Where does CO2 come from?
natural sources: respiration/photosynthesis
manmade sources: deforestation/burning fossil fuels
Why are O2 and N2 not greenhouse gases?
they don’t absorb IR radiation
can’t vibrate = can’t trap heat
What is the fossil fuel contribution to atmospheric CO2?
6-7 billion tons of carbon released
–> 1/2 goes into the atmosphere
Increasing CO2 levels
Since 1860:
-concentration: 290-385ppm
-increases 1.5 ppm/year
excess CO2 = global warming = big concern
How much does an atom weigh?
depends on the atom
What is the standard for atomic weight?
one Carbon-12 = 12 amu
atomic mass = 12.01 (weighted average atomic mass for carbon –> no carbon atoms actually equal 12.01 amu)
What does the 12 mean in Carbon-12?
mass #, total protons = neutrons
Weighing Carbon
can’t weigh individual atoms
define in grams, not amu
–> 12g C contains 6.022 x 10^23 carbon atoms
Conversions
grams—-(use molar mass)—–> moles —-(use Avagadro’s #)—–> atoms/molecules
How many atoms are in .551g of K?
8.49 x 10^21 atoms K
What is molecular mass (or molar mass)?
the sum of the atomic masses (in amu) in a molecule
–>mass of one mole of “anything” in grams
What is the molecular mass of SO2? Molar mass?
- 07amu
64. 07g
How many moles of C3H8O are in 72.5g?
1.2 moles
- one mole of CO2 = ________
2. has molar mass of…..?
- 6.022 x 10^23 molecules CO2
2. 12.01 + 16 + 16 = 44.01 g
What is a chemical reaction telling?
substances –> new substances
What is a chemical equation telling?
reactants –> products
How do you read this equation?
2Mg + O2 –> 2MgO
- two atoms Mg + one molecule O2 makes 2 MgO units
- two moles Mg + one mole O2 makes two moles MgO
- 48.6g Mg + 32g O2 makes 80.6g MgO
NOT: 2g Mg + 1g O2 makes 2g MgO
How to solve stoichiometry problems
- Balance chemical equation
- Convert to grams of known substances into moles
- Use coefficients - calculate # of moles unknown
- Convert moles to grams
What is the Global Warming Potential (GWP)?
relative contribution of a molecule of an atmospheric gas to global warming
Loss of Polar Ice Cap
- year round sea ice in arctic is decreasing 9% per decade
- ocean warms/ice melts –> more solar energy absorb by water creating pos feedbacks –> more ice melting
- impacts water salinity, changes marine habitats, and widens shipping lanes (adds pollution)
What is one way to reduce the severity of the greenhouse effect?
CO2 sequestration - take CO2 out of atmosphere and compress it
Ozone Hole vs. Global Warming
Ozone Hole: O3, UV light, Montreal Agreement (US did sign)
Global Warming: CO2/CH4, IR radiation, Kyoto Protocol (US did not sign –> it charged each nation for CO2 emissions and US couldn’t scale back enough to not be fined)
What is the enhanced greenhouse effect?
When atmospheric gases trap and return over 80% of the heat energy radiated by the earth
What is global warming?
Increase in average global temps as a result of the enhanced greenhouse effect
