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C1b
1.1 Cracking Hydrocarbons

Fractions from crude oil can be broken down by thermal decomposition in a
catalytic cracker.
The fraction is vaporised and passed over a hot catalyst.
The cracking of fractions causes the molecules to split apart and form smaller
molecules.
Some of the smaller molecules are alkanes,…

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New polymers have been produced to replace traditional materials in many uses.
Polymers have been developed to coat fabrics that make them waterproof but are
able to let gases through,
New polymers have been developed for medicinal purposes.
Hydrogels (these are used in agriculture and food).
Smart polymers can be…

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Additives are used in foods to improve:
Appearance.
Flavour.
Texture.
Taste.
Shelf Life.
Additives can be natural products or synthetic chemicals.
Substances like salt, vinegar and sugar have been used as additives for ages.
There are six main types of additive:
Colours.
Preservatives.
Antioxidants.
Emulsifiers.
Acidity Regulators.
Flavourings.
E-numbers are…

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Tectonic plates move because of convection currents in the mantle, due to
radioactive decay.

3.3 The Earth's Past Atmosphere

The Earth's early atmosphere was formed by volcanic activity.
Consisted mainly of CO2. May have been water vapour, with traces of methane
and ammonia.
As plants colonised the Earth, the levels…

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