OCR F332 The Atmosphere

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Chemistry of Natural Resources: The Atmosphere
Bonding and Structure
(a) describe examples of giant covalent (network) structures, such as diamond and silicon (IV) oxide; explain
differences in physical properties of CO2 and SiO
2 in terms of their different structures
Giant molecular structures have a huge network of covalently bonded atoms . Diamond (carbon) and silicon (IV)
oxide are two examples of substances with giant molecular structures. The reason carbon and silicon atoms can
form this type of structure is that they can each form four strong, covalent bonds .
They both:
Have a tetrahedral structure
Are bonded to 4 atoms
High melting point
Insoluble in any solvent
Doesn't conduct electricity no free electron
Carbon Dioxide (CO2)
Silicon Dioxide (SiO2)
Covalent molecular structure discrete molecules Covalent network structure a giant repeating
with strong covalent bonds within and weak lattice of covalently bonded atoms with strong
intermolecular bonds between molecules covalent bonds throughout
Double bonds Single bonds
Low melting point High melting point
Soluble Insoluble
Kinetics
(b) recall (and explain in terms of collision theory) the way that concentration, pressure and surface area
affect the rate of a reaction
Concentration Increasing the concentration of the solution means the particles are closer together on
average so there are more frequent successful collisions.
Pressure Increasing the pressure of a gas means the particles are closer together so there are more
frequent successful collisions.
Surface Area A larger surface area of reactants means more particles can come in contact with the
other reactants so there are more frequent successful collisions.
(c) explain use the terms:
Enthalpy
Profile

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Chemistry of Natural Resources: The Atmosphere
Equilibria
(g) explain and use the terms: dynamic equilibrium (rates of forward and back reaction equal; constant
concentrations of reactants and products; takes place in a closed system)
Dynamic equilibrium is when the forward reaction and backwards reaction equals. The concentrations of
reactants and products remain the same and can only happen in a closed system.…read more

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Chemistry of Natural Resources: The Atmosphere
Parts per million (ppm) is used instead of working with small percentages. Some gases are present in small
amounts that's not very convenient to write their quantities are percentages.…read more

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Chemistry of Natural Resources: The Atmosphere
Reaction Mechanisms
(m) describe the difference between homolytic and heterolytic bond fission and recognise examples
Breaking a covalent bond is called bond fission. A single covalent bond is a shared pair of electrons between two
atoms. It can break in two ways:
Heterolytic Fission Homolytic Fission
In heterolytic fission, both the shared electrons go to In homolytic fission, one electron goes to one atom and
one of the atoms when the bond breaks.…read more

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Chemistry of Natural Resources: The Atmosphere
Applications of Organic Chemistry
(p) explain why some properties of CFCs made them such useful compounds and discuss the relative advantages
and disadvantages of replacement compounds for CFCs: hydrochlorofluorocarbons (HCFCs), hydroflurocarbons
(HFCs) and hydrocarbons
CFCs (chlorofluorocarbons) are made up of chlorine, fluorine and carbon atoms they are halogenoalkanes . They
are unreactive , nonflammable and harmless which made them useful for fire extinguishers , as propellants in
aerosols and as the coolant gas in fridges.…read more

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Chemistry of Natural Resources: The Atmosphere
The ozone can also cause photochemical smog , which can be extremely irritating to the respiratory tract, leading
to coughing and various medical conditions if exposure is prolonged.
(r)recall and discuss aspects of the research leading to the discovery of the ozone layer and how the evidence
was first overlooked
In 1970s, the British Antartic Survey found that the concentration of ozone over Antarctica was very low
compared to previous measurements.…read more

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Chemistry of Natural Resources: The Atmosphere
(u)calculate values for frequency and energy of electromagnetic radiation using the equation E = h
E
= h
E = Energy in Joules
h = Planck's Constant (6.63x1034 )
v = Frequency in Hz
(v)explain the `greenhouse effect' in terms of:
(i) solar energy reaches Earth mainly as visible and UVs
(ii) Earth absorbs some of this energy, heats up and radiates IR
(iii) greenhouse gases (e.g.…read more

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Chemistry of Natural Resources: The Atmosphere
(x)recall and discuss different approaches to the control of carbon dioxide emissions:
Burning fewer fossil fuels Biodiesel/bioethanol ­ plants absorb the CO2 that is created in his process
(alternative fuels and (carbon neutral).
economy of use) Hydrogen ­ only produces water.
Nuclear power ­ doesn't create CO2 .
Electricity generation is a major use of fossil fuels ­ making sure appliances
aren't left on will reduce the amount of CO 2 made.…read more

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