GCSE OCR 21st Century Chemistry Air and Water Complete Revision Summary

This page contains the detailed and easy notes for GCSE OCR 21st Century Chemistry Air and Water for revision and understanding Air and Water .

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GCSE OCR 21st Century Chemistry Air and Water Complete Revision Summary

Air and Water

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Air and Water

  • Present Earth’s Atmosphere
  • The Earth’s Early Atmosphere
  • Increase in Oxygen
  • Decrease in Carbon Dioxide
  • Greenhouse Effect
  • Global Warming
  • Air Pollution
  • Atmosphere Pollutants




PRESENT EARTH’s ATMOSPHERE

Gases

 

Percentage (%)
Nitrogen78%
Oxygen21%
Argon0.9%
Carbon Dioxide0.04%
Trace of other gasesless than 0.1%

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EARLY EARTH’s ATMOSPHERE

VOLCANIC ERUPTION

Carbon Dioxide(CO2), Water(H2O) and Nitrogen(N2)

Water vapour condensed, rained and form oceans

Ice comets melted, rained and made water bodies

Stabilities Earth Atmosphere with no oxygen and life had carbon dioxide, water, nitrogen, with ammonia and methane in traces.
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EVOLUTIION OF OXYGEN

  • 7 billions years ago simple organisms converting chemical into energy evolved.
  • 7 billions years ago algae and bacteria that can photosynthesis evolved.
  • The plants increased the concentration of oxygen sustaining life.
  • Plants colonised sea and land and then animals evolved.

 DECREASE IN CARBON DIOXIDE

  • Used up by the plant in photosynthesis
  • Carbon dioxide got locked up in the rocks when the dead plants and animals died and decayed.
  • Carbon dioxide locked up in sea and also formed fossils fuels like coal, natural gas.

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WHY NITROGEN CONTENT IS HIGHER ?

  • Nitrogen is stable and unreactive gas.
  • It is released in large amount by early volcanic activities.
  • Ammonia and methane were released in small quantities which reacted with oxygen to form nitrogen and carbon dioxide.
  • Nitrogen being unreactive build up in the atmosphere.

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GREENHOUSE EFFECT

It is warming effect found in green house by allowing solar radiations to pass in but preventing long wave heat radiations to pass out due to glass panes, water vapours and carbon dioxide.

GLOBAL WARMING

Rise in mean temperature of the earth. It is due to the excess amount of green house gases present in the atmosphere

  • Climate Change
  • Habitat Loss
  • Floods
  • Change in Migration of Birds
  • Change in distribution of plants and animals
  • Change in seasonal pattern
  • Loss of Biodiversity causing extinction of species.

Air and Water

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REDUCING CARBON FOOTPRINTS

  • Carbon footprint is the total amount of carbon dioxide and other green house gases released
  • Carbon capture and storage where carbon dioxide released from powerstations is pumped underground into the rocks to cut down emissions.
  • Using biofuel as they are carbon neutral
  • Finding alternative source of energy to reduce the dependency on fossil fuels.
  • Carbon sequestration is the process of collecting the carbon dioxide in solid or the liquid form.

AIR POLLUTION

ACID RAIN

Formation

Sulphur and nitrogen present in fossil fuels forms carbon dioxide and sulphur dioxide by combustion.

Carbon dioxide and sulphur dioxide combine with rainwater forming nitric acid and sulphuric acid and falls as acid rain.

Effects

  1. a) Makes soil acidic
  2. b) Damage trees and aquatic life
  3. c) Corrossion of building
  4. d) Errodes building and rocks

Prevention

  1. a) Decrease in use of fossil fuels.
  2. b) Treat the waste to remove nitrogen and sulphur before evolving.
  3. c) Use alternative source of energy.

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SMOG

Smog is opaque or dark fog having condensed water vapours, dust, smoke and gases.

  • Mixture of nitrogen dioxide and sulphur dioxide particulates in the lower atmosphere.
  • Depletes ozones layer, cause dimming effect.
  • Lowers the Earth’s temperature
  • If inhaled causes damage to lungs, respiratory problems and cardiovascular diseases.


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KEY TERMS

Atmosphere – The earth is surrounded by a huge mantle of air called the atmosphere. It is maintained on our planet by its gravitational attraction.

Fossil Fuels – A hydrocarbon fuel, such as oil, coal or natural gas, derived from the accumulated remains of ancient plants and animals and used as fuel.

Sedimentary Rocks – Sedimentary rocks are often deposited in layers and often contain fossils.

Greenhouse effect – It is warming effect found in green house by allowing solar radiations to pass in but preventing long wave heat radiations to pass out due to glass panes, water vapours and carbon dioxide.

Global Warming – Rise in mean temperature of the earth. It is due to the excess amount of green house gases present in the atmosphere

Climate Change – Climate change refers to significant changes in global temperature, precipitation, wind patterns and other climate measures that occur over several decades.




Particulates – Particulate matter is a mixture of dangerous solid and liquid particles in the air. The types of polluting particles are fog, dust, smoke and smoke particles.

Global Dimming – It is defined as the decrease in the amount of solar radiation reaching the Earth’s surface.

Combustion – It occurs when any organic material is reacted (burned) in the presence of oxygen to give off the products of carbon dioxide and water and Energy

Incomplete Combustion – A reaction or process that involves only the partial combustion of a fuel. This could be due to lack of oxygen or low temperature, which prevents complete chemical reaction.
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Disclaimer:

I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.

References:

BBC Bitesize

Wikipedia

Wikimedia Commons

Image Source:

Wikipedia

Wikimedia

Commons

Flickr

Pixabay

Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.

 The Earth’s Atmosphere