science

chemistry bits and bobs

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  • Created by: catherine
  • Created on: 08-07-08 16:06

limestone

Limestone - mainly calcium carbonate

Used for:- building materials, making glass, making cement, neutralise lakes and rivers.

How is it obtained???? - Thermal decompotion

When heated it breaks down to QUICK LIME (calcium oxide) which is then used for it's reaction in water, for example it neutralises the acidicity of rivers and lakes.

Cement is made by roasting powered limestone mixing it with powered clay, water and so forth to produce concrete.

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crude oil

Crude Oil - mixture of compounds hydrocarbons

Used for- petrol, refinary gases, air craft fuel, diesal, ship fuel, roads.

obtained by - fractional distillation

The materials above need to be separated from the organic crude oil, they have due to the different sizes in molecules they have different boiling points. Fractional distillation works through heating, cooling and condensing.

Those with larger molecules, therefore higher boiling points they are less volatile and are less useful. These material can be briken down even further by a process calledCRACKING. (vapourising through hot catalyst - thermal decomposition)

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metals

Metals - from the earths crust

used for - Transition metals (belong in the middle group)have many useful properities their good conductors of electricity, heat and can be shaped easily.

how are they obtained- Depending their reactivity metals can be separated from they ores through either electrolysis or through reduction with carbon.

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earths atmosphere

Earth's atmosphere - Made up mainly of nitrogen (78%), oxygen (21%) and other gases, noble gases like argon, CO2(0.04) and water vapour.

Used for- oxygen is used in respiration, argon is used for bollons as it is less denser then air and nylon lights as it lights up when electicity is past through it.

Fuels used are made up of hydrocarbons in combustion, when there is enough air the hydrocarbon is oxide into carbon dioxide, this can increase carbon dioixe in the air.When there notenough air it produces harmfulsubstances like CARBON MONOXIDE and SULFUR DIOXIDE which are harmful to the earths atmosphere.

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Generating electricity

Nuclear energy - nuclear reactions to produce energy, the disadvantage of this is the waste needs to be stored for many years, it can be harmful and is very active.

Fossil fuels - energy is release through burning fossil fuels. There are two main disadvantages to this it's a non-renewable source, it also produces alot of carbon dioxide and other harmful gases.

Wind farms - Renewable energy, depends on the wind to generate eletricity. Disadvantage (as some moany gits may say, they are noisy and spoil the view)

Wave kinetic energy - Dependant ontide and wavescan destroy the wild life in rivers opening.

Solar energy - Can only be used when the sun is out!!!

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