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Unit 2 Module 4 Notes

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CHEMISTRY

2.4.1 CHEMISTRY OF THE AIR GREENHOUSE GASES


Water vapour Carbon dioxide Methane

ABSORPTION OF INFRARED RADIATION


Molecules of H2O, CO2 and CH4 Absorbed by C=O, O-H and C-H bonds Molecule vibrates

VIBRATING MOLECULES


Vibrate, rotate, stretch Emit energy in form of radiation Radiation absorbed by greenhouse gas molecules

DETERMINANTS OF THE GREENHOUSE EFFECT OF A GAS

Atmospheric concentration in atmosphere Ability to absorb IR radiation

ABSORPTION-EMISSION PROCESS

Keeps heat close to Earth's surface

GLOBAL WARMING





Climate change Caused by increase in greenhouse gases (burning coal, oil etc.) Causes flooding Causes extreme storms Causes ice to melt Causes rising sea levels

STOPPING GLOBAL WARMING

Reduce carbon dioxide emissions by 70-80%

CHEMISTS' ROLE IN MINIMISING CLIMATE CHANGE

Provides scientific evidence to governments verifying global warming Monitors progress of initiatives

INITIATIVES


Kyoto protocol Development of non-carbon fuels (wind, solar power etc.) Hydrogen fuel cells for cars

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Using renewable resources (biofuels etc.) EU targets Cleaner cars (less emissions of CO2)

CARBON CAPTURE AND STORAGE (CCS)

Sequestration Captures CO2 from power stations and stores it away safely

STORAGE IN OCEANS (CCS)

Liquid carbon dioxide injected deep in the oceans

STORAGE UNDERGROUND (CSS)

Store CO2 gas in underground porous rock (acts as a sponge) Keep it from leaking away

STORAGE AS CARBONATES




Storing carbon in stable minerals Reaction between CO2 and metal oxides Producing stable carbonates E.g. CaO (s) + CO2 (g)  CaCO3 (s) E.g. limestone rock (CaCO3)

Ozone


O3 Continuously being formed and broken down Broken down in stratosphere by UV radiation

CHEMICAL EQUILIBRIUM

O2 + O ↔ O3

CYCLE



UV radiation breaks O2 molecules into two oxygen atoms O atoms react with O2 molecules Process generates heat O3 absorbs UV and converted back to O2 and O

BALANCE OF OZONE IN OZONE LAYER

Ozone is being formed at the same rate as it is being broken down Stable balance

BENEFITS OF THE ABSORPTION OF UV BY OZONE


Process protects living organisms from harmful effects of UV Ozone layer filters out short wavelengths Ozone converts UV into heat

CFCs

Non-toxic
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