20 - Fuels Flashcards
What are natural gas and crude oil formed from?
Ancient remains of microscopic animals and plants that once lived in the sea
What is a Finite resource?
Something useful that is no longer made or which is being made very slowly
How are natural gas and crude oil formed?
- The remains of animals and plants become covered by layers of sediment
- Over millions of years, the remains gradually turn into natural gas and crude oil
- Sediment turns into rock, trapping the gas and oil
What is Crude oil?
A complex mixture of hydrocarbons formed from dead microscopic organisms (by heat & pressure) over millions of years
What is a Hydrocarbon?
A compound that contains hydrogen and carbon atoms ONLY
How many bonds can each carbon atom form?
And what type of bonds are these?
4
Covalent bonds
How many carbon atoms can there be in a hydrocarbon molecule?
It can vary from one to many hundreds of them
What state is Crude oil at room temperature?
Liquid
What are some uses of crude oil?
- Fuels for aircraft, vehicles, heating & power stations
- Feedstock
- Raw chemicals for the petrochemical industry
What are petrochemicals?
Substances made from crude oil such as polyethene & other polymers
What is Natural gas?
A mixture of Hydrocarbons in the gas state formed from the remains of dead plants and animals that lived in the sea
What is the main hydrocarbon in Natural gas?
Methane
What is Methane useful for?
Cooking
What is the definition of Non-renewable?
Any energy resource that will run out because you cannot renew your supply of it
e.g. Oil
Why can Crude oil be separated using fractional distillation?
The different hydrocarbons have different boiling points
What is Fractional distillation?
A method of separating a mixture with different boiling points to individual components (fractions)
What is a Fractionating column?
A long column used for Fractional distillation.
Its warmer at the bottom & colder at the top
Label the fractionating column
What is the acronym you can use to remember the fractionating column order?
Bald fuming dwarves killed Patricia’s gerbils
Describe the temperatures in the fractionating column
Column is hottest at the top and coldest at the bottom
Describe how crude oil is separated into different fractions
- Vapours rise through the column & cools down
- Vapours condense when they reach a part of a column that is below their bp
- Liquid falls into a tray & is piped away
What fraction has the highest boiling point?
Bitumen
What fraction has the lowest boiling point?
Gases
Which fraction has the highest num of atoms in molecules?
Bitumen
Which fraction has the lowest num of atoms in molecules?
Gases
Which fraction has the highest ease of ignition?
Gases
Which fraction has the lowest ease of ignition?
Bitumen
Which fraction has the highest viscosity?
Bitumen
Which fraction has the lowest viscosity?
Gases
Give some uses for the gases fraction
Domestic heating & cooking
Give some uses for the petrol fraction
Fuel for cars
Give some uses for the Kerosene fraction
Fuel for aircraft
Give some uses for the Fuel oil fraction
Fuel for large ships & in some power stations
Give some uses for the Diesel oil fraction
Fuel for some cars and trains
Give some uses for the Bitumen fraction
Surface for roads & roofs
Describe the properties of fractions
Each fraction has:
* Similar numbers of carbon and hydrogen atoms in their molecules
* Similar bp
What are alkanes?
Hydrocarbon that only have single covalent bonds between the atoms in their molecules
What is the homologous series?
A family of compounds that have the same general formula and similar properties but have different numbers of carbon atoms
What are the characteristics of members in the homologous series?
- Similar chemical properties
- Same general formula
- Show a gradual variation in physical properties (e.g. bp)
- Molecular formulae of neighbouring compounds differ by Ch2
What is the general formula for the alkanes?
When does complete combustion of a hydrocarbon fuel occur?
When there is a good supply of air
What type of reaction is the complete combustion of hydrocarbon?
Exothermic
What does the complete combustion of hydrocarbons produce?
- Carbon dioxide & water
- Max amount of energy is given out
What does the incomplete combustion of hydrocarbons produce?
- Water is produced
- Energy is given out (but less)
- Carbon monoxide
- Carbon
Why is carbon monoxide produced during the incomplete combustion of hydrocarbons?
Some carbon atoms in the hydrocarbon may still fully be oxidised to Co2 bur some are only partially oxidised to CO
—> Some Carbon atoms are released as smoke and soot
What are the problems of incomplete combustion?
- Can cause problems in appliances that uses hydrocarbon fuels if they are poorly maintained/ unventilated
- CO is toxic to inhale - can cause CO poisoning
- Soot can block pipes, blacken buildings & cause breathing problems
Explain how carbon monoxide is a toxic gas?
It combines with haemoglobin in red blood cells, preventing O2 from combining
—> Reduces amount of O2 carried in bloodstream
—> Severe CO poisoning can cause death
What is acid rain?
Rain with a pH lower than 5.2
Name some substances that causes acid rain?
Sulphur dioxide & Nitrogen dioxide
What impurities do Hydrocarbon fuels contain?
Sulphur compounds
How do Hydrocarbon fuels produce sulphur dioxide gas?
When hydrocarbon fuel is burnt, sulphur reacts with O2 to form sulphur dioxide gas
What are the problems of acid rain?
- Crops don’t grow well when soil is too acidic
- Excess acidity can kill fish and insects
- Increases rate of weathering of buildings made of limestone/marble
- Increases the rate of corrosion of metals
Why do limestone/marble react with acid rain?
Rocks are almost pure calcium carbonate which reacts with sulphuric acid
What is the word equation for the reaction of sulphuric acid and calcium carbonate?
What colour is nitrogen dioxide?
Red-brown
What are the problems with nitrogen gas on the human body?
Can cause respiratory diseases (e.g. Bronchitis)
What part of the car converts most of the NO into harmless nitrogen?
Catalytic converters
What does Nitrogen dioxide form when it dissolves in the water in clouds?
Dilute nitric acid
Why do car engines produce oxides of nitrogen?
Inside car engines, fuel is mixed with air and ignited inside the engine
—> Causes temperatures high enough for nitrogen and oxygen in the air inside the engine to react together
What are the advantages of using hydrogen as a fuel compared to petrol?
- Environmentally friendly compared to using Co2 (greenhouse gas)
—> Only produces water
What are the disadvantages of using hydrogen as a fuel compared to petrol?
- Hydrogen is difficult to store as it’s a gas at room temp
- Easily ignited
What is the solution to storing hydrogen for fuel?
It can be compressed under high pressure or liquified by cooling
What is cracking?
A chemical reaction in which large alkane molecules are split into two or more smaller alkanes & alkenes
What is cracking useful for?
To match supply with demand of fuels
—> Supply of some fractions is greater than it’s customer demand
Explain how cracking is conducted
Crude oil fractions are heated to evaporate them
Vapours are passed over a catalyst & heated to 650 degrees
—> This speeds up reactions that break down larger hydrocarbon molecules
What compound does the catalyst need to contain when cracking hydrocarbons?
Aluminium oxide
What can the smaller hydrocarbon molecule product of cracking be used for?
As fuels or for making polymers
What is the difference between alkenes and alkanes?
- Alkenes are UNsaturated
- Alkanes are Saturated
What does being a Saturated molecule mean?
Carbon atoms are joined by single bonds (C-C)
What does being a Unsaturated molecule mean?
Contain a carbon-carbon double bond (C=C)
Where is methane found?
Natural gas
What is methane?
Non-renewable fossil fuel
