The Atmosphere F332 with ideas

Includes all of the Storyline information from The Atmosphere module in F332 Chemistry Salters OCR, natural resources.

It also includes all of the relevant Chemical Ideas, with 10 questions at the end of each storyline sub-topic.


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  • Created by: Xavier
  • Created on: 15-05-12 13:36
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Page 1

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Chemistry Revision
The Atmosphere


A1 ­ What's in the air?
A2 ­ Screening the Sun
A3 ­ Ozone: A vital sunscreen
A4 ­ The CFC story
A5 ­ What is the state of the ozone layer now?
A6 ­ The greenhouse effect
A7 ­ Trouble in the troposphere…

Page 2

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The atmosphere is a thin layer of gas extending 100km above Earth's surface

Chemically important regions are the troposhphere and stratosphere.
As altitude increases, density decreases.

90% of molecules in the atmosphere lie in the lower region called the troposphere.

The concentrations of substances are either measured as percentages…

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Mixing is different in the reverse temperature gradient of the stratosphere: mixing rarely occurs
in the vertical direction, but does occur in horizontal circulation.

6.2 ­ What happens when radiation interacts with matter?

EM radiation transfers energy to chemicals.
These chemicals absorb energy and changes occur.
The changes depend…

Page 4

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Vibrational energy: corrresponds to IR
(we sense IR as heat, bonds in chemicals in our skin vibrate more energetically, the energy is
converted to KE which warms us up).

Rotational energy: corresponds to a lower frequency radiation ­ Microwaves

Translational energy: is even less, it is so small that…

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The following can occur with high frequency EM radiation, in increasing energy:

Electrons may be excited to a higher energy level (electrons excited, return to ground
state, light is emitted). E.g. with chlorine, green light is emitted.
Electrons in a bond may photodissociate into radicals
Electrons are able to…

Page 6

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The sun radiates a wide spectrum of energy.

Some corresponds to the energy required to break chemical bonds ­ even in DNA.
This can cause damage in genes and cause skin cancer.
Years of exposure can make people look wrinkly and leathery: radiation damages proteins of
connective tissue beneath…

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All reactions involve the breaking and remaking of chemical bonds.

Bond breaking = bond fission

Two types = Heterolytic fission and Homolytic fission

Heterolytic fission

Both shared electrons go to just 1 atom
Two ions are formed
It is common when a bond is already polar

E.g. bromomethane


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Even O2 has two unpaired electrons, and so is a biradical: however it is relatively stable.

Radicals are reactive. Filled outer electron shells are more stable than unfilled ones.

When a Cl radical collides with a H2 molecule, it will steal the electron from the H2 bond and form…

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CH3Cl + Cl2 CH2Cl2 + HCl

For every Cl2 molecule used, 1 H atom is replaced on the halogenoalkane, and one HCl (H-Hal) is

In summary,

Radical chain reactions usually occur in the gas phase or in a non-polar solvent
They are often initiated by heating or by…

Page 10

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Ozone is being made and destroyed all the time.
If left to themselves, the rate of proucing ozone = the rate of destroying ozone.
I.e. they are in a "steady state." But not with human inteference!

Reaction (2) should equal reactions (4) and (5). However, when taking measurements we…


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