F335 STORYLINES NOTES

Notes on the Chemical Storylines for the F335 exam.

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  • Created on: 25-05-13 16:50
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22/05/13
F335 STORYLINES NOTES
AGRICULTURE AND INDUSTRY
1. Growing one crop multiple times on the same soil can destroy the soil's fertility by
depleting specific nutrients. Agricultural technology appropriate for one place may
not be suitable for another because of differences in growing conditions and soil
types. Sustainable farming is agriculture that can go on indefinitely without
degrading the environment.
2. Soil is a mixture of weathered rock fragments (mineral matter) and organic matter
(plant/animal remains and excreta) making a porous fabric capable of holding air and
water. During decomposition, elements in organic compounds are converted into
inorganic ions - mineralisation. Essential ions are held in the soil because clay minerals
can bind positive ions to their surfaces. H+ can displace metal ions in clay soils, making
the soil more acidic. If the pH of soil is too low then crop growth is restricted. Basic
carbonates can be added to make it less so. The amount needed depends on the
soil's buffering capacity is it's capacity to resist the base's neutralising action. The
soil acts as buffer when the base is first added as it resists the pH change. It can do
this as the H+ in soil replace some H+ in soil solution.
3. Humus is a group of organic compounds found in soil, formed from the
decomposition of plant and animal remains by micro-organisms. Major components
are esters and phenols. If these lose H+ ions the negative groups can ionically bond to
metal cations so humus can hold a variety of nutrient ions like clay.
4. Plants draw nutrients from an inorganic store partly in soil and partly on top. The
organic store (on top and in soil) is replenished by manure, excretions and
death/decay of living organisms. Weathering of soil and rock minerals releases ions
into the organic store (in soil). Nutrients can lost from both by leaching out of the top
layers by rainwater, and nitrogen can be lost by conversion into gases.
5. Nitrogen is added to soil through fixation, where some bacteria in soil and legume
root nodule convert N2 gas to NH4+. Lightning, natural fires and burning hydrocarbon
fuels produce nitrogen oxides which are deposited in soil. Nitrogen is lost from soil
through denitrification, leaching, loss of ammonia gas and uptake by plants.
Denitrification is where anaerobic bacteria reduce nitrate(V) in steps to N2 gas.
Leaching is when nitrate(V) ions which are not held by clays or humus drain away in
rainwater. Leaching is reduced when winter crops are grown. Nitrogen is
transformed in soil through mineralisation and nitrification. Mineralisation is when
organic nitrogen compounds are broken down to NH4+ by several steps. NH4+ is
converted to nitrate(V) ions by some micro-organisms. Nitrification is when NH4+ is
oxidised by some aerobic bacteria to produce nitrate(III) which is then oxidised to
nitrate(V).
6. Organic chemistry is the study of compounds of carbon, excluding CO2 and CO.
Organic farming uses fertilisers and pesticides of only plant/animal origin. A strict
set of rules must be followed during food production. SA* doesn't allow chemically
synthesised fertilisers. Farmers use crop rotation schemes (land has time to
regenerate nutrients), grow crops that are ploughed back into soil (green manures -
fix nitrogen), apply compost/manures (increase nitrogen content directly). and
apply certain permitted mineral fertilisers e.g. sulfur.
7. In the Haber process, nitrogen and hydrogen from the air are reacted together with
an iron catalyst in a vessel at 400-500oC and 25-150 atmospheres. Most ammonia is
used in inorganic fertilisers in salt or liquid form. The range includes ammonium

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V) ammonium sulfate and ammonium phosphate. Some ammonia is used in
the fermentation industry to adjust pH.
8. Pesticides (insectides, herbicides, fungicides) kill insects that eat our crops,
weeds that compete with the crops for soil nutrients, and moulds that rot plants and
seeds. Some are banned, e.g. DDT, which can remain in the soil, accumulate in food
chains, and affect predators and contaminate food supplies (or leach into water
supplies).…read more

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A paint is usually made up of two main parts: the colouring matter (pigment) and the
liquid that carries the pigment and allows it to spread and bind to a surface (binder).
The binder must be viscous enough to prevent paint from running but not too sticky
otherwise the artist's freedom would be restricted.
7.…read more

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Salt was used to preserve food before
refrigerators and freezers were invented.
3. Underneath the sediments of the ocean floor are lavas, generated by long, thin
underwater ridges. Lava and gases high in chlorine, bromine and sulfur compounds
well up from the ridges, and water percolating through hot lava dissolves these
compounds.
4. The distinctive smell of the seaside if caused by dimethyl sulfide, a volatile gas.…read more

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Water is one of the
best substances for doing this so has a high cp.
11. Salty water is denser than pure water, and water is denser when it is colder.…read more

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MATERIALS REVOLUTION
1. Cholesterol is a lipid found in cell membranes. There are two types; LDL and HDL. LDL
carries cholesterol around the body where it is deposited in arteries causing
narrowing and eventually blockage. HDL collects cholesterol and transports it to the
liver to be broken down. Statins lowers blood cholesterol levels. Mevastatin was the
first compound to significantly inhibit cholesterol but higher doses were too toxic for
humans. Lovastatin had a similar inhibiting effect and was much less toxic.…read more

Comments

Sam

You don't have a similar document for the storylines of the F334 exam do you? Would be great!

Sam

By the way on the last page of the document the title is Material Revolution rather than Medicines by Design as I'm assuming its meant to be :)

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