Fuels And Earth Science Flashcards
How is crude oil separated into different hydrocarbon fractions
Fractional distillation
How is crude oil formed
Underground, over millions of years at high temperatures and pressure from the buried remains of plants and animals
What is crude oil
A complex mixture of lots of different hydrocarbons, containing molecules in which carbon atoms are in chains or rings an important source of useful substances
What is a hydrocarbon
Compounds which just contains hydrogen and carbon
What are hydrocarbons mostly
Alkanes
What are fractions
Simpler more useful mixtures containing groups of hydrocarbons of similar length
What are the 3 non-renewable fractions made from crude oil
Petrol, diesel, kerosene
How is fractional distillation done
The oil is heated until most of has turned to gas, the gas enters and fractionating column and the liquid is drained off
What hydrocarbons have higher boiling points
Longer hydrocarbons
What do shorter hydrocarbons have
Lower boiling points
What does the fractionating column have
A temperature gradient
What are all the fractions made by crude oil
Kerosene, petrol, bitumen, diesel, gases, fuel oil
What is a homologous series?
A family of molecules which have the same general formula and share similar chemical properties
What are the two different homologous series of Hyde
Alkanes and alkenes
What does the sis sod a hydrocarbon determine
It’s properties
What are the physical properties determined by
The intermolecular forces that hold the chains together
Why do hydrocarbons make good fuels
Because the combustion reactions that happen when you burn them in oxygen give out lots of energy - exothermic
When does incomplete combustion happen
When a hydrocarbon burns in a limited supply of oxygen
Complete combustion word equation
Hydrocarbon + oxygen — carbon dioxide + water
Complete combustion symbol equation
C(3)H(8) + 5O(2) — 3CO(2) + 4H(2)O
What does incomplete combustion produce
Toxic carbon monoxide and soot
What does carbon monoxide do
Combine with red blood cells and stop your blood fro, doing it’s proper job of carrying oxygen around the body
What is the formula for alkanes
C(n)H(2n+2)
What does sulfur dioxide cause
Acid rain
What does acid rain do
Kills tress, damages limestone buildings and stone statues, makes metal corrode
Pros of hydrogen
Very clean fuel, renewable resource
Cons of hydrogen
You need a special expensive engine, hard to store
What does cracking do
Turns long saturated (alkane) molecules into smaller unsaturated (alkene) molecules
What is thermal decomposition
When one substance breaks down into at least 2 new ones when you heat it
What does cracking produce lots of
Alkene molecules
What is the catalyst used for cracking
Aluminium oxide
What is a homologous series
A family of molecules which have the same general formula and share similar chem properties
What happens in the complete combustion of hydrocarbon fuels
Carbon dioxide and water are produced and energy is given out
What are gases used for
Domestic heating and cooking
What is kerosene used for
Fuel for aircraft
What is diesel oil used for
Fuel for some cars and trains
What is fuel oil used for
Fuel for Large ships and in some power stations
What is bitumen used for
To surface roads and roofs
What are the 4 ways hydrocarbons in different fractions differ from each other
The number of carbon and hydrogen atoms their molecules contain, boiling points, ease of ignition, viscosity
Why do big molecules have higher boiling points than small molecules
The intermolecular forces of attraction break a lot more easily in small molecules than in bigger molecules - the forces are much stronger between big molecules
Why are shorter carbons easy to ignite
Because they have lower boiling points so tend to be gases as room temp, these gas molecules mix with oxygen in the air to produce a gas mixture which bursts into flames if it comes into contact with a spark
What fractions have a higher viscosity
Fractions containing longer hydrocarbons
When does incomplete combustion happen
When a hydrocarbon burns in a limited supply of oxygen
How does carbon monoxide behave as a toxic gas
It can combine with red blood cells and stop your blood from doing its job of carrying oxygen around the body, a lack of oxygen in the blood supply to the brain can lead to fainting, a coma or death
What does incomplete combustion produce
Carbon monoxide, carbon dioxide, water, carbon(soot)
What does soot do
Makes buildings look dirty, reduces air quality and can cause or worsen respiratory problems
Where does sulfur dioxide come from
Sulfur impurities in the fossil fuels
How is sulfuric acid formed
When sulfur dioxide mixes with clouds it formed dilute sulfuric acid which falls as acid rain
What does acid rain do
Causes lakes to become acidic and many plants and animals die as a result, it kills trees, damages limestone buildings and stone statutes and can make metal corrode
How are nitrogen oxides produced
Created from a reaction between oxygen in thr air and nitrogen, caused by the energy released by combustion reactions, for example, in the internal combustion engines of cada
What do nitrogen oxides contribute to
Acid rain and can cause photochemical smog
Advantages of using hydrogen instead of petrol as fuels for cars
Very clean, only waste product is water - no nasty pollutants, obtained from water which is renewable source
DisAdvantages of using hydrogen instead of petrol as fuels for cars
U need a special expensive engine, hydrogen gas also needs to be manufactured which is expensive and often uses energy from o another source - burning fossil fuels which produces pollutants, hard to store and not widely available
What is methane and where’s it found
Non renewable fossil fuel found in natural gas
Why are a lot of the longer molecules produced from fractional distillation are cracked into smaller ones
There’s more demand for products like petrol and diesel than for bitumen and fuel oil
Why is cracking useful
It helps to match the supply of fractions with the demand for them.
How was the early atmosphere formed
By the gases produced from volcanic activity
What was the earths early atmosphere thought to contain
Very little oxygen, water vapour, large amount of carbon dioxide, small amount of other gases
How were oceans formed in the early atmosphere
Condensation of water vapour
Why did the amount of co2 in the atmosphere decrease when oceans formed
It dissolves readily in water. As the oceans formed, carbon dioxide dissolved to form soluble carbonate compounds so its amount in the atmosphere decreased. Carbonate compounds were then precipitated as sedimentary rocks, eg limestone.
How did the amount of oxygen in the atmosphere gradual increase
The growth of primitive plants used carbon dioxide and released o2 by photosynthesis so amount of o2 increased
How do u test for o2
If a glowing splint relights
What is the greenhouse effect
Various gases in the atmosphere including carbon dioxide, methane and water vapour absorb heat radiated from the earth subsequently releasing energy which keeps the earth hot
How is methane increasing
Methane is produced in the digestive processes of certain livestock e.g. cattle, goats and camels
How is the amount of co2 going up
Human population is increasing so there are more people respiring giving out more co2
And burning fossil fuels gives off lots of co2
What are the effects of global warming
Changing rainfall patterns, Severe flooding due to polar icecaps melting
