Topic 8 - Fuels and Earth Science Flashcards
What is crude oil a main source for?
Hydrocarbons
What forms crude oil?
Millions of years of high temperature and pressure on buried remains of plants and animals
What type of resource is crude oil?
Non-renewable (finite)
How is crude oil seperated?
It is heated until most of it has turned into gas and then enters a fractionating column
Describe the relation between hydrocarbon length and boiling point?
The longer the hydrocarbon, the higher the boiling point
Give the order of the hydrocarbons released from the fractionating column
Gases Petrol Kerosene Disel Fuel Bitumen
What is used for cooking and heating?
Gases
What are gases used for?
Cooking and heating
What is disel oil used in?
Fuel for cars and larger vehicles (eg Trains)
What is fuel oil used for?
Fuel for ships and power stations
What is bitumen used for?
Surfacing of roads and roofs
What three things must you be able to describe crude oil as?
A complex mixture of hydrocarbons containing molecules in which carbon atoms are in chains or rings
An important source of useful substances (fuels and
feedstock for the petrochemical industry)
A finite resource
Explain how crude oil is separated into fractions during fractional distillation?
Oil is heated until most of it turns into gas
Gases enter a fractionating column and the liquid part is drained off at the bottom
Since there’s a temperature gradient, the column is hot at the bottom and cooler at the top
The longer HC’s turn back into liquids and drain out lower down the column
Whilst, the shorter HC’s turn into liquids and drain out higher up the column
Explain how crude oil is separated into fractions during fractional distillation?
Oil is heated until most of it turns into gas
Gases enter a fractionating column and the liquid part is drained off at the bottom
Since there’s a temperature gradient, the column is hot at the bottom and cooler at the top
The longer HC’s turn back into liquids and drain out lower down the column
Whilst, the shorter HC’s turn into liquids and drain out higher up the column
What does the temperature gradient mean?
The column is hotter at the bottom and cooler at the top
What is a homologous series?
A family of molecules which have the same general formula and share similar chemical properties
Give examples of a homologous series of hydrocarbons
Alkenes
Alkanes
Give an example of a non-hydrocarbon homologous series
Alcohol
What is similar among compounds in a homologous series?
They have the same general formula
They differ by CH2 in molecular formulae from neighbouring
compounds
They show a gradual variation in physical properties (eg. Boiling point)
They have similar chemical properties
What determines which fraction a hydrocarbon will come out of?
It’s length (size)
What physical properties are there to do with hydrocarbons?
Ease of ignition
Boiling point
Viscosity
How does length of a hydrocarbon affect the boiling point?
The longer the HC, the higher the boiling point
Why does length of a hydrocarbon affect the boiling point?
The longer the HC, the stronger the intermolecular forces of attraction meaning the harder they are to break therefore a high temperature is needed
How does length of a hydrocarbon affect the ease of ignition?
The longer the HC, the harder to ignite
Why does length of a hydrocarbon affect the ease of ignition?
The shorter the HC, the more likely they are gases meaning they are easier to ignite than liquids
Why is it easier for a gas to ignite?
Because it will mix with oxygen in the air to produce a gas mixture which will burst into flames if in contact of a spark
How does length of a hydrocarbon affect the viscosity?
The longer the HC, the more viscous the liquid
Why does length of a hydrocarbon affect the viscosity?
The longer the HC, the stronger the intermolecular forces meaning harder it is for the liquid to flow
What is viscosity?
The measure of how easily a substance flows
What do fuels release in combustion reactions?
Energy
Why are hydrocarbons great fuels?
Their combustion reactions release alot of energy (very exothermic)
What is the complete combustion equation?
Hydrocarbon + Oxygen -> Carbon Dioxide + Water
Finish the balanced symbol equation to show the complete combustion of C9H20!
C9H20 + _O2 -> _H20 + _CO2
C9H20 + 14O2 -> 10H20 + 9CO2
What does complete combustion produce?
Carbon Dioxide and Water
What does incomplete combustion produce?
Carbon Dioxide, Carbon Monoxide, Water and Soot
Explain why the incomplete combustion of hydrocarbons can
produce carbon and carbon monoxide?
There is less oxygen therefore the products will have much less oxygen
Why is carbon monoxide toxic?
Because it can combine with erythrocytes, stopping blood from carrying oxygen
And a lack of oxygen in the blood supply to the brain can cause fainting, a coma or even death
Why is soot bad?
It can make buildings look dirty, reduce air quality and cause or worsen respiratory problems
What other harmful gases do fossil fuels release when burned?
Nitrogen oxides and sulfur dioxide
Where does the sulfur dioxide come from in the fossil fuels?
The sulfur impurities
What happens to the sulfur dioxide released from combustion?
Some of it will be mix with the clouds to form dilute sulfuric acid which will then fall as acid rain
Whats the problems with acid rain?
May cause lakes to become acidic which will kill animals and plants, trees damaged, buildings damaged and metal may corrode
When are nitrogen oxides produced?
When nitrogen and oxygen in the air react because of energy released by combustion reactions
When are nitrogen oxides commonly produced?
In the internal combustion engines of cars
Why are nitrogen oxides harmful?
They can contribute to acid rain and can cause photochemical smog
What is photochemical smog?
A type of air pollution that can cause breathing difficulties, headaches and tiredness
What are the pros of hydrogen in cars?
Very clean fuel
Only product is waste (water)
Obtained from a renewable resource (water)
Water can be recycled to get hydrogen
What are the cons of hydrogen in cars?
Special, expensive engine needed
Hydrogen has to be manufactured meaning it will be expensive and will require another external energy source which is most likely non renewable and produces pollutants
Hydrogen is hard to store
Hydrogen is not widely available
Name two pollutants formed by incomplete combustion
Carbon monoxide and soot
What is cracking?
The splitting up of long-chain hydrocarbons
What does cracking ‘convert’?
Long saturated alkane molecules into smaller unsaturated alkene and alkane molecules
What is cracking a form of?
Thermal decomposition
What is thermal decomposition?
The breaking of one substance into a t least two new ones when you heat it
What is often added to help cracking?
A catalyst?
Why does cracking involve such high energy (temperatures)?
Because strong covalent bonds must be broken
Why are alot of the longer molecules broken up by cracking?
Because:
There’s more demand for products like petrol and diesel than for bitumen and fuel oil
Alkene molecules produced can be used to make polymers
Briefly describe how cracking is done?
Vaporised hydrocarbons are passed over powdered catalyst at high temperatures and pressures
What is the catalyst used in cracking?
Aluminium oxide
Why does the process of cracking require lots of energy?
Because strong covalent bonds must be broken within the alkane molecules
When a molecule of C17H36 is cracked, two molecules are made
C5H10 is produced, what is the chemical formula of the other molecule?
17-5=12
36-10=26
C12H26
What did volcanoes give out?
Mainly carbon dioxide but some ammonia, steam and methane
Describe what the Earth’s early atmosphere was thought to
contain?
Little or no oxygen
Large amount of carbon dioxide
Water vapour
Small amounts of other gases (Methane and Ammonia)
What happened to the water vapour?
It condensed to form the oceans
What happened to most of the early carbon dioxide?
It dissolved into the oceans
What two things caused a rise in nitrogen gas?
Ammonia reacting with oxygen
Denitrifying bacteria
What caused the amount of nitrogen to increase and never really decrease?
Nitrogen is very unreactive
What caused the rise in oxygen?
The evolution of green plants
What did green plants do to the atmosphere?
They photosynthesised releasing oxygen and taking in carbon dioxide
What happened to carbon dioxide that wasn’t used in photosynthesis or in the oceans?
Locked up in fossil fuels and sedimentary rocks
What did the build of oxygen do?
Killed off early organisms that couldn’t tolerate it
Allowed the evolution of more complex organisms
Created the ozone layer which blocked harmful rays from the sun
What is the test for oxygen?
A glowing splint relighting
Why does an increasing population mean more energy?
There are more that need lighting, heating, cooking, transport, housing and food
Why has carbon dioxide in the atmosphere increased over the last 150 years?
The human population has increased rapidly
Lifestyles are changing
Why is deforestation bad?
Fewer plants means less carbon dioxide taken out of the atmosphere
What does the Sun give out?
Electromagnetic radiation
What type of EM radiation are absorbed by the the Earth?
EM waves with short wavelengths
What does the absorbed radiation do to the planet?
Heat it up
What happens to the absorbed radiation absorbed by the Earth?
Some is radiated which is then either:
Asorbed by the greenhouse gases
Re-emitted back towards the Earth by the greenhouse gases
Re-emitted into space
What are greenhouse gases?
Gases in the atmosphere which absorb and reflect heat radiation
Give examples of greenhouse gases
Carbon dioxide, water vapour and methane
Give two reasons why the increasing human population has affect levels of atmospheric carbon dioxide
Any two from:
More land needed so more deforestation, less carbon dioxide absorbed for photosynthesis
More people so more carbon dioxide given out by respiration
More energy needed for transport/cooking/lighting so more carbon dioxide released from burning of fossil fuels
What ways are there to estimate past data?
The analysis of fossils, tree rings or gas bubbles trapped in ice sheets
What are the problems of estimating past data?
Much less precise and much less representative of global levels
What is global warming?
A type of climate change where the Earth’s average temperature has increased
Give measures we can take to reduce carbon dioxide emissions
Walk or cycle instead of drive, turn your central heating down or use more renewable energy
Name two applications of hydrocarbons?
Any two from: Cooking Heating Fuel (Eg. Planes, Trains, Automobiles...) Surfacing of roofs and road
How is crude oil formed?
Millions of years underground of very high heat and pressure
Which elements are HC made from?
Hydrogen and Carbon
What is the purpose of fractional distillation?
To seperate the mixtures of hydrocarbons from the crude oil
Do longer or shorter HC drain out the bottom?
Longer
What types of molecules are produced by cracking?
A smaller alkane and alkene
Describe the composition of todays atmosphere
78% Nitrogen 21% Oxygen >1% Carbon Dioxide >1% Noble Gases >1% Water Vapour
