Fuels
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- Created by: squeaky biscuit
- Created on: 08-12-14 18:45
Crude oil
- Hydrocarbons are compounds which only contain hydrogen and carbon
- Crude oil is a complex mixture of hydrocarbons
Crude oil fractions
- Crude oil is heated in a heater and separated into simpler, more useful mixtures. Which are:
- Gases- used in domestic heating and cooking
- Petrol- Used as a fuel for cars
- Naphtha
- Kerosene- Used as fuel for aircrafts
- Diesel oil- Used as fuel for some cars and trains
- Fuel oil- Used as fuel for large ships and in some power stations
- lubricating oil
- Bitumen- Used to surfaces roads and roofs
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Crude oil fractions and combustion
- Hydrocarbons in different fraction differ from each other in:
- Number of carbon an hydrogen atoms their molecules contain
- boiling points
- ease of ignition
- Viscosity
Combustion
- Complete combustion of hydrocarbons:
- involves oxidation of the hydrocarbons
- produces carbon dioxide and water
- gives out energy
- The chemical test for finding carbon dioxide is that you bubble the gas through limewater. if it turns milky then the gas is carbon dioxide
- Word equation for the reaction when methane burns:
- methane + oxygen -> carbon dioxide + water
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incomplete combustion and acid rain
- Incomplete combustion of hydrocarbons can produce carbon and carbon monoxide because there is not enough oxygen for all the carbon atoms to form carbon dioxide
- Carbon monoxide is a toxic gas because it replace oxygen on the red blood cells
- Problems with carbon monoxide are it is:
- Odourless
- colourless
- toxic
- lethal
- methane + oxygen àcarbon dioxide+ carbon monoxide + carbon (soot) + water
- Impurities in some hydrocarbon fuels result in the production of sulphur dioxide because when the fuel is burnt the sulphur reacts with oxygen from the air to form sulphur dioxide.
- The effects of acid rain include:
- Making rivers, lakes and soils acidic- this harms organisms living there.
- damaging trees
- speeding up weathering of buildings made of limestone or marble and the corrosion of metal
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climate change
- Various gases in the atmosphere trap heat from the sun this keeps the earth warm
- The proportion of carbon dioxide in the atmosphere varies, due to human activity.
- Chemist are investigating the amount of carbon dioxide there is in the atmosphere by:
- iron seeding of oceans
- converting carbon dioxide into hydrocarbons
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Biofuels
- Biofuels are a possible alternative to fossil fuels
- Ethanol is a biofuel obtained by processing sugar cane or sugar beet
- Advantages of biofuels:
- biofuels are renewable
- They may help reduce the amount of carbon dioxide human activity puts into the atmosphere
- can be carbon neutral
- good alternatives to fossil fuels
- Disadvantages:
- Not carbon neutral if you account for transport and process of burning them
- Need a lot of crops so they take up space which could be used for growing food
- can lead to deforestation
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Biofuels
- Biofuels are a possible alternative to fossil fuels
- Ethanol is a biofuel obtained by processing sugar cane or sugar beet
- Advantages of biofuels:
- biofuels are renewable
- They may help reduce the amount of carbon dioxide human activity puts into the atmosphere
- can be carbon neutral
- good alternatives to fossil fuels
- Disadvantages:
- Not carbon neutral if you account for transport and process of burning them
- Need a lot of crops so they take up space which could be used for growing food
- can lead to deforestation
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Choosing fuels
- Factors that make a good fuel are :
- it is easy to burn
- produces a small amount of ash or smoke
- produces a small amount of heat
- it is easy to store and transport
- Advantages of using hydrogen instead of petrol as fuel in cars:
- renewable resource
- Disadvantages:
- Expensive
- Not easy to buy
- releases carbon dioxide
- Petrol, kerosene and diesel are non-renewable resources obtained from crude oil
- Methane is a non-renewable resource found in natural gas
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Alkanes and alkenes and cracking
- Alkanes are saturated hydrocarbons, which are present in crude oil.
- Alkenes are unsaturated hydrocarbons
- If bromine water (pale yellow to red-brown in colour) is mixed with a saturated hydrocarbon it will stay the same colour. If it is mixed with and unsaturated hydrocarbon the colour fades away.
- Cracking involves the breaking of larger alkanes into smaller, more useful ones, some of which are alkenes.
- Cracking is necessary because there is a higher demand for smaller alkanes than what is available.
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Polymerisation
- Many ethene molecules can combine in a polymerisation reaction
- The polymer formed is called polyethene
- Other polymers can be made by combing together other monomer molecules
- Reusing is when you use a substance more than once when it is in its original form
- Recycling is when you change an object into something different before you use it again.
- Some problems associated with the disposal of polymers can be overcome by recycling or by developing biodegradable polymers.
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