Air and Water

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  • Created by: Lotto65
  • Created on: 22-12-15 17:35

Gases in the Atmosphere

There are many gases in air of varying proportions...

Nitrogen= 78%

Oxygen= 21%

Carbon Dioxide= 0.04%

Argon= 0.9%

Other gases= Traces (technically 0.06%) --> water vapour included

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Fractional Distillation of Air

PRODUCES PURE LIQUID OXYGEN AND NITROGEN GAS

1) Air is filtered to remove dust

2) Air is cooled to -200 degrees Celcius to become a liquid

3) As it cools, water vapour condenses and is removed

4) Then, carbon dioxide freezes and is also removed

5) Remaining air enters fractionating column---> warmer at bottom

6) At -185 degrees celcius at the bottom and -190 degrees celcius at the top, the oxygen remains as a liquid and exits through the bottom

7) Nitrogen boils into a gas and leaves through the top

8) A separate distillation process takes place to separate oxygen from argon which leave the tower together as liquids

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Oxygen and Oxides

Reactive gas in air --> Oxygen

When we burn something, it reacts with oxygen (combustion) in the air to form oxides

Metal oxides are solids and basic --> Non -metal oxides are gases and acidic

Some oxides are neutral e.g. water and carbon monoxide

Amphoteric oxides --> Dissolve in acids like a base but react with alkalis like an acid so behave like both --> Aluminium oxide and Lead oxide

These reactions are examples of oxidation where oxygen is added

Oxygen removed from oxide --> reduction --> extraction of metals from ores --> Iron  (III) oxide reduced to iron in blast furnace

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Water Treatment

Drinking water --> Low level of salts and microbes --> NO HARMFUL SUBSTANCES

Treatment process --> Sedimentation and filtration to remove solids --> Sterilisation to kill microbes using chlorine         Or distillation --> Expensive as lots of energy required

Desalination --> Few sources of natural freshwater so seawater converted to usable water

--> Distillation at lower pressure and boiling point to save energy

Test for pure water --> Boils at 100 degrees Celcius

For fluoridation of waater supplies --> Dental health improves

Against --> People have no choice and cannot measure how much each person gets

Filter Jugs --> Carbon (reduces chlorine levels and other organic impurities); Ion exchange resin ( Removes calcium, magnesium, lead, copper and aluminium ions); Silver nanoparticles ( Discourage growth of bacteria in the filter)

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Rusting

Corrosion of iron to form hydrated Iron (III) oxide

NEEDS WATER AND OXYGEN FOR SOMETHING TO RUST

Iron + Oxygen + Water --> Hydrated Iron (III) Oxide

Preventing rusting:

Coat in Oil --> Grease --> Paint --> Less reactive metal --> More reactive metal --> Plastic

Sacrificial protection --> Coat in more reactive metals (zinc, magnesium, aluminium) --> Works even if coating is scratched or iron is exposed

Rust indicator --> Turns blue at first signs of rust --> Used in experiments

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