Chemistry AQA GCSE revision Unit 1 C1

Got me an A* so this should help you if you're studying AQA GCSE chemistry - hope it helps and please rate! :)

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  • Created on: 02-03-13 12:37
Preview of Chemistry AQA GCSE revision Unit 1 C1

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Chemistry
Evolution of the atmosphere
Volcanoes gave out gases
1. The Earths surface - molten for millions of years until the Earth cooled and the crust formed. Volcanoes
kept erupting.
2. The volcanoes gave out lots of gas. This was how the oceans and atmosphere formed
3. The early atmosphere was mostly CO2 with no oxygen. There was also water vapour, ammonia and
methane
4. The Oceans formed when the water vapour condensed
Green plants evolved and produced oxygen
1. Green plants and algae thrived in the CO2 atmosphere
2. A lot of the early CO2 dissolved in the oceans
3. The green plants and algae also used up CO2 and produced O2 by photosynthesis
4. Plants, algae and marine organisms died and were buried under layers of sediment. The carbon and
hydrocarbons inside them became `locked up' in sedimentary rocks and fossil fuels
5. When we burn fossil fuels, the `locked up' CO2 is released and the concentration of CO2 in the
atmosphere increases
Ozone layer allows evolution of complex animals
1. Increasing O2 in the atmosphere: killed off some early organisms & created the ozone layer which
blocked harmful rays from the sun, allowing other more complex organisms to evolve
Crude oil
Crude oil is a mixture of many compounds
Hydrocarbons are fuels such as petrol or diesel
The hydrocarbon molecules aren't bonded to each other
The parts of a mixture can be separated out by physical methods
Fractional Distillation of Crude Oil
The more volatile the gas/liquid, the shorter the molecule and the quicker you can condense it.
Cracking crude oil
1. Long-chain hydrocarbons are turned into smaller ones by a process called cracking
2. Cracking is a thermal decomposition reaction
3. You heat the long-chain hydrocarbon molecule to vaporise it
4. The vapour is then passed over a powdered catalyst (aluminium oxide)
5. Most of the products of cracking are alkanes and alkenes
Plant Oils
Some fruits and seeds contain oil e.g. avocados and olives
These oils can be extracted and used for food or fuel

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The plant material is crushed
2. The crushed plant material is pressed between metal plates and the oil is squashed out
3. Oil can be separated from crushed plant material by a centrifuge OR solvents can be used to get oil
from plant material
Distillation refines oil and removes water, solvents and impurities
Hydrogenation of unsaturated oils
1. Unsaturated oils are liquid at room temperature
2. They can be hardened by reacting them with a nickel catalyst at about 600C. THIS IS HYDROGENATION.…read more

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