C1.4 Crude oil and fuels Flashcards
What is crude oil?
A mixture of compounds which are hydrocarbon molecules
Define ‘mixture’
Two or more elements/compounds not chemically combined, with the chemical properties of each substance unchanged
Where is crude oil derived from?
An ancient biomass found in rocks
What is the general formula for alkanes?
Cn H2n+2
What are alkanes?
Saturated hydrocarbons with as many hydrogen atoms as possible bonded to each carbon
What are the first four alkanes and their formulas?
- Methane (CH4)
- Ethane (C2H6)
- Propane (C3H8)
- Butane (C4H10)
Explain the process of fractional distillation.
- Crude oil is heated to 350c degrees and vaporised
- As vapours rise up the fractionating column they cool and condense
- The hydrocarbons are different lengths so their vapors condense at different times at different points in the column
- They are trapped off as liquids at the levels they condense in the column
What is similar about fractions from crude oil?
They have a similar number of carbon atoms
What do the properties of hydrocarbons depend on?
The length of their molecules
The shorter the hydrocarbon molecule…
- The less viscous
- The more volatile
- The lower the boiling/melting point
- The more flammable
What do most fuels contain?
- Carbon
- Hydrogen
- May also contain sulfur
What is usually released when fuels are burnt?
- Carbon dioxide
- Water vapour
- Carbon monoxide
- Nitrogen oxide (at very high temperatures)
- Sulphur dioxide
- Solid particles (soot)
What happens during the combustion of hydrocarbon fuel?
- Energy is released
- The carbon and hydrogen in the fuels are oxidised
What is combustion?
A chemical reaction of a fuel with oxygen that releases energy
What are advantages of using crude oil?
- Most modern transport is fueled by a crude oil fraction
- So is central heating and electricity
- It is a large industry
- Many materials e.g plastics are made from crude oil
- Most machinery is set up for oil fractions e.g cars and they are readily available e.g many petrol stations
- More reliable than eco alternatives e.g wind turbines
What are disadvantages of using crude oil?
- Non-renewable
- Oil spills disrupt environment and animals e.g sea otters and birds are poisoned
- Burning it causes global warming, acid rain and global dimming (more detail later)
What do carbon dioxide emissions cause?
- A rise in global temperature
- This means changing rainfall patterns and flooding
When does a fuel release sulphur dioxide?
If it contains sulphur impurities
What do sulphur dioxide emissions cause?
- They mix with water in clouds to make sulfuric acid
- This falls as acid rain
- This kills trees and damages limestone buildings
How can acid rain be reduced?
- By removing sulphur from the fuel (this is expensive and uses more energy though)
- By putting acid gas scrubbers in petrol stations to take harmful gases out before they are released into the atmosphere
What do nitrogen oxide emissions cause?
- Acid rain in clouds as well (nitric acid)
- Smog
What is incomplete combustion?
When there is not enough oxygen and some of the fuel doesn’t burn
What does soot cause?
- Global dimming
- The particles reflect sunlight back into space
- They also produce more clouds which reflect sunlight back into space
What does carbon monoxide cause?
It is a poison to humans, reducing the amount of oxygen carried by the blood
Give 3 examples of alternative fuels being developed.
- Ethanol
- Biodiesel
- Hydrogen gas
How is ethanol made and what is it used for?
The fermentation of plants
- To power cars
What are the advantages of ethanol?
- Carbon neutral
- Only product other than carbon dioxide is water
What are the disadvantages of ethanol?
- Engines need to be converted
- Ethanol fuel not widely available
- Increase in food prices as land is used to grow fuel crop
How is biofuel made and what is it used for?
- Produced from vegetable oils e.g rapeseed oil and soybean oil
- To run a biodiesel engine
What are the advantages of biofuel?
- Carbon neutral
- No need to convert engines
- Less sulphur dioxide and soot than ordinary diesel
What are the disadvantages of biofuel?
- Not enough to completely replace diesel
- Expensive
- Increase in food prices
How is hydrogen acquired and what is it used for?
- From the electrolysis of water
- To power vehicles
What is the advantage of hydrogen gas?
- Hydrogen combines with oxygen in the air to form just water (very clean)
What are the disadvantages of hydrogen gas?
- Special, expensive engine needed
- Hydrogen not widely available
- Hard to store
- Electrolysis needed = energy
