Fuels and Earth Science

What is crude oil?

• A fossil fuel formed over millions of years from the remain of marine organisms

• It is a complex mixture of hydrocarbons

• There are multiple fractions crude oil can be split into

What are hydrocarbons?

Compounds of only hydrogen and carbon

What are finite resources

Resources that are no longer being made or are made extremely slowly

How can crude oil be separated and why?

By fractional distillation because the hydrocarbons that make up crude oil have different boiling points

What happens during the fractional distillation of crude oil?

• The oil is heated to evaporate it

• The column has a temperature gradient-hotter at the bottom and cooler at the top

• Each fraction can cause one part of the crude oil to condense

How does the length of a chain in a hydrocarbon affect it’s boiling point?

• As the length of the chain increases, the boiling point of the hydrocarbon also increases

• This means that in fractional distillation, the shortest chains will rise to the highest part of the fractionning column

What are the different fractions of crude oil?

Gases, petrol, kerosene, diesel oil, fuel oil, bitumen

What is the fraction gases of crude oil used for?

Domestic heating and cooking

What is the fraction petrol of crude oil used for?

Fuel for cars

What is the fraction kerosene of crude of oil used for?

Fuel for aircraft

What is the fraction diesel oil of crude oil used for?

Fuel for some cars and trains

What is the fraction fuel oil of crude oil used for?

Fuel for large ships and some power stations

What is the fraction bitumen of crude oil used for?

Surfacing roads and roofs

What is a homologous series?

A family of compounds with a general formula they all follow

What are the products of the complete combustion of an alkane?

Carbon dioxide + water

What is the bonding like between all atoms in an alkane?

Only single bonds

What is the general formula for alkanes

C_nH_2n+2

What happens during the complete combustion of a hydrocarbon?

• Hydrogen is oxidised to make H20 (water)

• Carbon is oxidised to make CO2 (Carbon dioxide)

• Energy is transferred to the surroundings by radiation as heat and light

What are the products of the incomplete combustion of a hydrocarbon?

• Water is still produced just like in complete combustion

• Carbon is partially oxidised to make CO (Carbon monoxide)

• Carbon may be released as carbon particles or soot

• Less energy is given out than complete combustion

Why is it hard to detect carbon monoxide?

It is odourless and colourless

What are the symptoms of carbon monoxide poisoning?

Dizziness, chest pain, headache, breathing problems, drowsiness

What things can release carbon monoxide?

• There is always incomplete combustion in vehicle engines

• Faulty gas boilers can produce carbon monoxide and soot

Is rainwater alkaline, acidic or neutral?

Acidic

What pH does rainwater have to be to be considered acid rain?

Less than 5.6

How is acid rain formed?

• Hydrocarbon fuels can contain impurities such as sulfur compounds

• These impurities oxidise to form sulfur dioxide when the fuel is burnt in power station and vehicles

• This sulfur dioxide dissolves in rainwater to form an acidic solution

What are the affects of acid rain?

• Speeds up the weathering of buildings and statues

• Trees are damaged

• Rivers, lakes and soil are more acidic, harming organisms living in them

How can we reduce environmental damage caused by acid rain?

• Removing sulfur from petrol, diesel oil and fuel oil at an oil refinery before selling it

• Prevent sulfur dioxide leaving power stations through chimneys

• Adding calcium carbonate or calcium hydroxide to neutralise excess acid from the rain

What are non-renewable resources?

Resources that are being used up faster than they are being produced

What are the products of the combustion of hydrogen?

Hydrogen + Oxygen → Water (This water is water vapour)

How is hydrogen manufactured for fuel in cars for example?

• Electrolysis of water

• Cracking of oil fractions

• Reaction of natural gas with steam

What are the advantages of using petrol as a fuel?

• Burns easily

• Does not produce ash

• Releases more energy per kg when it is burnt than other fuels like wood or coal

• Being a liquid, it is easy to store and transport

What are the disadvantages of using petrol as a fuel?

• Produces carbon dioxide and carbon monoxide as well as water when it is burnt

• Carbon monoxide is a poisonous substance

• Carbon dioxide contributes to the greenhouse effect

What are the advantages of using hydrogen as a fuel?

• Burns easily

• Does not produce ash or smoke

• Only produces water when it burns

• Releases nearly three times as much energy per kg when burnt than petrol

What are the disadvantages of hydrogen as a fuel?

• Is a gas, so it has to be stored at a high pressure which can be dangerous

• Filling stations would need to be adapted for hydrogen to be used in cars

• Hard to store because it is a gas

What is cracking?

Breaking down large hydrocarbon molecules into smaller, more useful hydrocarbons

What was the early atmosphere comprised of?

• Little or no oxygen

• A large amount of carbon dioxide

• Water vapour

• Small amounts of other gases

What evidence do we have for what the early atmosphere of Earth was comprised of?

• The mixture of gases released by volcanoes

• Other planets in our solar system

What was the Earth’s early atmosphere caused by?

Volcanic activity that released a mixture of gases into the air

What is today's atmosphere comprised of?

• 78% Nitrogen

• 21% Oxygen

• 1%- Other gases including argon, water vapour and carbon dioxide

How did oxygen levels increase over time on Earth?

• Earth cools and water vapour condenses, causing oceans to form

• Forms of life evolve in the oceans and they photosynthesise

• Oxygen builds up in the oceans

• Oxygen builds up in the atmosphere

How did levels of carbon dioxide decrease over time on Earth?

• Carbon dioxide dissolved in the oceans

• Some marine organisms used this carbon dioxide for photosynthesis, taking carbon dioxide out of the air and releasing oxygen

• Other marine organisms used the dissolved carbon dioxide to make calcium carbonate for shells

• The shells of dead marine organisms fall to the sea bed and become part of the sediment

• Over millions of years the layers of sediment become squashed and form sedimentary rocks

What is the greenhouse effect useful for and why is it also a problem?

• The greenhouse effect keeps Earth warm enough for organisms to exist

• If too much heat is trapped it can cause global warming and climate change

What happens in the greenhouse effect?

• Greenhouse gasses in the atmosphere absorb heat radiated from the Earth

• The greenhouse gasses then release this energy in all directions, keeping the Earth warm

What are the three main greenhouse gasses and what are their sources?

• Carbon dioxide- burning fossil fuels

• Methane- livestock farming e.g cattle, landfills

• Water vapour- evaporation from oceans

Why is water vapour seen as a much less problematic greenhouse gas?

Water vapour leaves the atmosphere as rain and snow

What happens when greenhouse gasses are released into the atmosphere?

They absorb infrared radiation warming up the atmosphere

What is global warming?

An increase in the warming effect of the atmosphere

What is climate change and what is it’s effect??

• Long term changes to weather patterns

• Rising sea levels due to melting ice caps

• Unusual weather patterns

What happens to the heat and light energy emitted from the sun when it comes to Earth?

• Earth absorbs most of the radiation

• Some is emitted back into space

• Some is emitted from the Earth to gases in the atmosphere

• Some of these gases may re-emit this infrared radiation

What are the two techniques for cracking?

• Thermal cracking- Large hydrocarbons heated up to 730^oC and 70 atmospheres

• Catalytic cracking- Large hydrocarbons heated to 500^oC over a zeolite catalyst

How does carbon monoxide behave as a toxic gas?

• Carbon monoxide reacts with haemoglobin in blood

• Stops oxygen being carried by haemoglobin in blood, so less oxygen reaches the brain