FOSSIL FUELS and the CARBON CYCLE

Doc Brown's GCSE/IGCSE/O Level KS4 science-CHEMISTRY Revision Notes

Oil, useful products, environmental problems, introduction to organic chemistry

1. Fossil Fuels - where do they come from? and the Carbon Cycle

What is a fossil fuel? What is the origin of coal, peat, oil, natural gas? What is the Carbon Cycle? These revision notes on the use of fossil fuels and relationship with the carbon cycle, should prove useful for the NEW AQA GCSE chemistry, Edexcel GCSE chemistry & OCR GCSE chemistry (Gateway & 21st Century) GCSE (91), (9-5) & (5-1) science courses.


GCSE/IGCSE/O Level Oil Products & Organic Chemistry INDEX PAGE

ALL my Advanced A Level Organic Chemistry revision notes


1. The origin of oil and other fossil fuels - what are they formed from?

  • Advanced Chemistry Page Index and LinksCrude oil is formed from organic material of the remains of plant and animal organisms that lived millions of years ago.  These remains form sediments e.g. at the bottom of seas, and  become buried under layers of sedimentary rock. They  decay, without air (oxygen), under the action of heat and pressure to form crude oil over millions of years.

    • Crude oil is a non-renewable energy resource taking millions of years to form from degraded organic biomass, so we are consuming fossil fuels at a much faster rate than they are being formed.

    • The vast majority of compounds found in crude oil are hydrocarbons, that is compounds/molecules made up of carbon atoms combined with hydrogen atoms.

  • It is a fossil fuel because it is formed from once living organisms and the Sun is the original source of energy. It is a non-renewable and finite (limited reserves) energy resource because it takes millions of years to form and we burn it faster than its is formed! It is also known as a finite energy resource because it will eventually run out! We do not have unlimited oil reserves!

    • The majority of fossil fuels (e.g. oil and gas) are made of hydrocarbon compounds - molecules composed of carbon and hydrogen atoms, though coal is mainly carbon with small quantities of other elements.

  • Coal, peat and natural gas are the other principal non-renewable fossil fuels formed from the remains of plants or animals.

    • Coal, formed millions of years from the remains of tropical plant material, mainly consists of carbon,  Burning coal produces a lot of pollution as the greenhouse gas carbon dioxide. The pollutants include soot particles (black deposits of carbon), sulphur dioxide (lung irritant and acid rain gas) and poly-aromatic hydrocarbons which are carcinogenic.

      • The main reaction on burning is ...

      • carbon + oxygen ====> carbon dioxide

      • C(s) + O2(g) ====> CO2(g)

      • ... so the main product of burning coal is carbon dioxide

      • This is an example of an oxidation reaction - an atom (carbon) has gained oxygen (become combined with oxygen).

    • Natural gas, mainly the hydrocarbon methane CH4, is often found with oil. It consists of 25% by mass of hydrogen and 75% carbon, and, apart from the 'greenhouse' CO2, produces far less pollution than coal on combustion.

    • Peat ('turf') is formed over hundreds-thousands of years from the decay of plant material in the absence of oxygen, in boggy-water logged ground. It is a poor quality fuel since the carbon content is much less than in coal and large amount of ash formed on combustion. However, there is a peat fired power station in Ireland.

  • Advanced Chemistry Page Index and LinksTHE CARBON CYCLE: When the fossil fuels are burned the 'carbon', as carbon dioxide, is returned to the atmosphere of the Earth's environment. There, it gets absorbed by plant leaves and used up in photosynthesis with the help of sunlight energy and green chlorophyll. The plant material decays reforming carbon dioxide, or, is eaten by animals and used in respiration to form carbon dioxide. Either way, this completes the carbon cycle. See also evolution of Earth's atmosphere

    • photosynthesis: carbon dioxide + water ==> glucose + oxygen

      • 6CO2 + 6H2O ====> C6H12O6 + 6O2 

    • respiration: glucose + oxygen ==> carbon dioxide + water

      • C6H12O6 + 6O2  ====> 6CO2 + 6H2O

      • and fossil fuel combustion, forest fires etc. all return carbon dioxide to the atmosphere

    • Some of the carbon ends up as coal from decayed plants or oil from decayed animal remains i.e. fossil fuel formation, which ultimately also becomes part of the carbon cycle.

    • Until the industrial revolution, the processes in the carbon cycle were in equilibrium, however, the large-scale burning of fossil fuels is disturbing the balance between these same processes and carbon dioxide levels have been steadily rising, particularly over the last 200 years.

  • POLLUTION PROBLEMS from burning fossil fuels are dealt with in section 4. Pollution, carbon monoxide, sulfur/nitrogen oxides, acid rain, what makes a good fuel?, global warming-climate change

More on the CARBON CYCLE with reference to the diagram below

  • You need to be able to show an understanding of how carbon is recycled in the CARBON CYCLE (diagram above).
    • a) during photosynthesis plants remove carbon dioxide from the atmosphere
      • carbon dioxide + water == light energy/chlorophyll  ==> glucose + oxygen

      • This is the process by which plants make food, for themselves, and for most animal life, including us too!

      • Note that the only way carbon dioxide is removed from the air is photosynthesis in green land based plants or marine organisms like phytoplankton (this point ignores long term formation of carbonate rocks like limestone).

    • b) carbon compounds pass along a food chain
      • All food chains involve the passing of carbon compounds e.g. sugars, carbohydrates, fats and proteins up to the next trophic level i.e. the consecutive eating along a food chain (and waste produced on the way).
        • e.g. grass ==> cow ==> human
    • c) during plant or animal aerobic respiration organisms release carbon dioxide into the atmosphere
      • sugars e.g. glucose + oxygen ==> carbon dioxide + water (+ energy)
      • this is the main aerobic energy releasing process in most living organisms.
    • d) decomposers release carbon dioxide into the atmosphere - slow aerobic respiration
      • Microorganisms like bacteria and fungi in the soil feed off decaying plant material and animal droppings or remains.
      • Most dead plant matter consists of cellulose which most animals can't digest, but bacteria and fungi, do have the enzymes to break it down and without their help there would be no carbon cycle.
      • Most of these bacteria and fungi respire aerobically so they need a good supply of oxygen to produce the carbon dioxide essential to keeping the carbon cycle going.
    • e) combustion of fossil fuels releases carbon dioxide into the atmosphere
      • Coal, formed millions of years from the remains of tropical plant material, mainly consists of carbon,  Burning coal produces a lot of pollution as the greenhouse gas carbon dioxide.

        • The main reaction on burning is ...

        • carbon + oxygen ====> carbon dioxide

        • C(s) + O2(g) ====> CO2(g)

      • Natural gas (mainly methane) and petrol molecules like octane (and lots of other molecules) from oil and gas reserves.

        • methane + oxygen ===> water + carbon dioxide

        • octane + oxygen ===> water + carbon dioxide

 


GCSE/IGCSE/O Level Oil Products & Organic Chemistry INDEX PAGE

ALL my Advanced A Level Organic Chemistry revision notes

Multiple Choice Quizzes and Worksheets

KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products (easier-foundation-level)

KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products (harder-higher-level)

KS4 Science GCSE/IGCSE m/c QUIZ on other aspects of Organic Chemistry

and (c) doc b 3 linked easy Oil Products gap-fill quiz worksheets

ALSO gap-fill ('word-fill') exercises originally written for ...

... AQA GCSE Science (c) doc b Useful products from crude oil AND (c) doc b Oil, Hydrocarbons & Cracking etc.

... OCR 21st C GCSE Science (c) doc b Worksheet gap-fill C1.1c Air pollutants etc ...

... Edexcel GCSE Science Crude Oil and its Fractional distillation etc ...

... each set are interlinked, so clicking on one of the above leads to a sequence of several quizzes

 

Notes information to help revise KS4 Science Additional Science Triple Award Separate Sciences Chemistry revision notes for GCSE/IGCSE/O level Chemistry Revision-Information Study Notes for revising AQA GCSE Science AQA GCSE Chemistry, Edexcel GCSE Science, Edexcel GCSE Chemistry, OCR 21st Century Science Chemistry, OCR Gateway Science chemistry, WJEC/CBAC GCSE science-chemistry CCEA/CEA GCSE science-chemistry (and courses equal to US grades 8, 9, 10) GCSE chemistry IGCSE chemistry revision notes on fossil fuels KS4 GCSE Science revision notes on fossil fuels GCSE chemistry guide notes on fossil fuels for schools colleges academies science course tutors images pictures diagrams for fossil fuels science chemistry revision notes on fossil fuels for revising chemistry module topics notes to help on understanding of fossil fuels university courses in science careers in science jobs in the industry laboratory assistant apprenticeships technical internships USA US grade 8 grade 9 grade10 AQA chemistry science GCSE notes on fossil fuels Edexcel chemistry science notes on fossil fuels for OCR 21st century chemistry science notes on fossil fuels OCR GCSE Gateway science chemistry notes on fossil fuels WJEC gcse science chemistry notes on fossil fuels CCEA/CEA gcse chemistry notes science O level chemistry notes for fossil fuels IGCSE chemistry revision notes on fossil fuels O level chemistry notes gcse chemistry revision free detailed notes on fossil fuels to help revise igcse chemistry igcse chemistry revision notes on fossil fuels O level chemistry revision free detailed notes on fossil fuels to help revise gcse chemistry free detailed notes on fossil fuels to help revise O level chemistry free online website to help revise fossil fuels for gcse chemistry  free online website to help revise fossil fuels for igcse chemistry free online website to help revise O level fossil fuels chemistry how to succeed in questions on fossil fuels for gcse chemistry how to succeed at igcse chemistry how to succeed at O level chemistry a good website for free questions on fossil fuels to help to pass gcse chemistry questions on fossil fuels a good website for free help to pass igcse chemistry with revision notes on fossil fuels a good website for free help to pass O level chemistry


ALPHABETICAL SITE INDEX for chemistry     

GCSE/IGCSE/O Level Oil Products & Organic Chemistry INDEX PAGE

ALL my Advanced A Level Organic Chemistry revision notes

 Doc Brown's Chemistry 

*

For latest updates see https://twitter.com/docbrownchem

TOP OF PAGE

visits since January 2000