C1.4 Crude Oil and Fuels Flashcards
What is crude oil?
A mixture of many different compounds, mainly made of hydrocarbons
Why do different parts of a mixture have different properties?
The different parts of the mixture aren’t chemically bonded - this means different parts of the mixture have different properties e.g. boiling points
How is crude oil separated?
With fractional distillation
How does the temperature change as you go up a fractionating column?
It’s hottest at the bottom and coldest at the top
What is the process of fractional distillation? (2)
- The crude oil is boiled and is piped into the bottom of the column
- The different compounds have different boiling points so they condense at different points in the column
How does the number of carbon atoms in a hydrocarbon affect it’s boiling point?
The more the carbon atoms, the higher the boiling points
How are the different groups of hydrocarbons collected in fractional distillation?
The hydrocarbons that condense together are called fractions, theses are tapped off from the column at the different levels they condense at
What are alkanes?
Chains of carbon atoms surrounded by hydrogen atoms - different alkanes have different lengths
What are the first 4 alkanes?
Methane CH4, ethane C2H6, propane C3H8* and butane C4H10
What is the structure of alkanes?
They contain carbon atoms which form 4 bonds, and hydrogen atoms which form 1 bond, there are no double bonds in alkanes and all the atoms are full saturated
What is the general formula for alkanes?
CnH2n+2, n is the number of carbon atoms
As you change the length of an alkanes molecule, how is viscosity affected?
The shorter the molecule chain, the less viscous it is
As you change the length of an alkanes molecule, how is volatility affected?
The shorter the molecule chain, the more volatile (= turns into gas at a lower temp)
As you change the length of an alkanes molecule, how is boiling temperature affected?
The shorter the molecule, the lower its boiling point
As you change the length of an alkanes molecule, how is flammability affected?
The shorter the molecules, the more flammable
What would a hydrocarbon which is a liquid and can be ignited be used for?
Petrol - car fuel
What would a hydrocarbon which is gloopy and viscous be used for?
Lubricating engines or covering roads
What is the equation for the complete combustion of a hydrocarbon?
When there is an adequate supply of oxygen:
hydrocarbon + oxygen ==> carbon dioxide + water vapour
What is produced when there is partial combustion? (5) What problems are there with one of the products produced?
When there isn’t an adequate supply of oxygen: solid particles of soot are produced, unburnt fuel is released, as well carbon dioxide, water vapour and carbon monoxide (which is poisonous)
What is produced when a fuel containing sulphur impurities is burnt?
Sulphur dioxide
What does sulphur dioxide cause?
Acid rain
What does acid rain cause? (4)
It causes lakes to become acidic so plants and animal die as a result of this, it also kills trees, damages limestone building and ruins stone statues
One way of reducing acid rain levels, is by removing the sulphur impurities, what’s wrong with this? (2)
It costs money and requires energy which releases more greenhouse gases
Besides removing the sulphur impurities, what other ways can acid rain be reduced? (2)
By disposing of the sulphur dioxide before it’s released into the atmosphere, Acid Gas Scrubbers are used in power stations to remove the gas, but we could just cut down on the use of fossil fuels to prevent acid rain
What does an increase in carbon dioxide levels result in?
An increase in the average temperature of the earth - global warming
What is global warming?
A type of climate change that causes other types of climate change e.g. changing rainfall patterns
What is global dimming?
Due to particles of soot and ash being produced by fossil fuels, the suns rays are reflected instead of reaching earth - the earth is getting darker
Why is the theory of global dimming sometimes neglected?
Because the stats showing that global dimming is a thing were considered to be measured using inaccurate equipment
What are biofuels?
Fuels made from plant material
What are two examples of biofuels?
Ethanol and biodiesel
How is ethanol made?
By the fermentation of plants
What are the advantages of using ethanol as a fuel? (4)
It is carbon neutral, the process of making ethanol doesn’t require much energy, ethanol is renewable as it’s made from plants, and growing the crops for ethanol is labour intensive which provides jobs for locals
What are the disadvantages of using ethanol as a fuel? (3)
Engines need to be converted before they can work with ethanol, ethanol fuel isn’t widely available (compared to petrol where there are petrol stations everywhere), and growing the crops for ethanol can replace farms which are growing food making food prices inc.
How is biodiesel made?
It can be produced from vegetable oils such as rapeseed oil and soybean oil
What are the advantages of using biodiesel as a fuel? (5)
Carbon neutral, renewable, provides jobs for locals, engines don’t need to be converted (as biodiesel can be mixed with diesel and work in a diesel engine), and it produces less sulphur dioxide and particulates than ordinary diesel and petrol
What are the disadvantages of using biodiesel as a fuel? (3)
We can’t make enough biodiesel to completely replace diesel, it’s expensive to make and like ethanol, growing the crops for biodiesel can replace food farms
How is hydrogen obtained?
From the electrolysis of water - this requires electrical energy, which can be obtained from renewable sources like solar
What are the advantages of using hydrogen as a fuel? (2)
When hydrogen is burnt it combines with air to produce water, so it is very clean, and the hydrogen comes from water which there is an abundance of
What are the disadvantages of using hydrogen as a fuel? (4)
An expensive, special engine is needed to use hydrogen as a fuel, hydrogen isn’t widely as a fuel, you still need another source of energy to make it, and hydrogen is hard to store as it is extremely flammable
