Fuels and Atmospheric Science Flashcards
What is crude oil?
A fossil fuel that is formed over millions of years from ancient remains of marine organisms, it is an important source of useful substances and it is a finite resource
What are hydrocarbons?
Compounds of carbon and hydrogen atoms only
What bonds can carbon atoms make in hydrocarbons?
Carbon-carbon and carbon-hydrogen
In terms of hydrocarbons what is crude oil?
A complex mixture of hydrocarbons with carbon atoms in chains or rings
What is a finite resource?
A resource that will run out because it is no longer being made or it is being made extremely slowly, crude oil is a finite resource because it takes millions of years to form
Why can crude oil be separated using fractional distillation?
Because its different hydrocarbons have different boiling points
How does fractional distillation work to separate crude oil?
- Crude oil is heated and vapours begin to rise up the fractionating column
- The column is hot at the bottom and cool at the top
- Each fraction condenses where it becomes cool enough and is piped out of the column
- The gases fraction does not condense and leaves at the top
- The bitumen fraction does not evaporate and leaves at the bottom
- The other fractions are liquid at room temperature so they’re useful as fuels
What happens to hydrocarbons in terms of physical properties as the number of hydrogen and carbon atoms increases?
- The strength of the intermolecular forces increases so more energy must be transferred to overcome these forces meaning the boiling point increases
What happens to the boiling point, ease of ignition and viscosity of a hydrocarbon as the number of hydrogen and carbon atoms increase?
- The boiling point increases
- The ease of ignition decreases, hydrocarbons become less flammable as the number of hydrogen and carbon atoms increase
- The viscosity increases, the hydrocarbon becomes more ‘thick’
What are most hydrocarbons from crude oil?
Alkanes
In a homologous series what does the molecular of the neighbouring member differ by?
CH2, neighbouring members also show a gradual variation in physical properties, for examples as CH2 is added the boiling point of that hydrocarbon increases
What happens to alkanes when they react with oxygen?
They undergo complete combustion
What is the general word equation for complete combustion?
Hydrocarbon + oxygen → carbon dioxide + water
What is the general word equation for incomplete combustion?
Hydrocarbon + oxygen → carbon monoxide + carbon + water
What is the general formula for an alkane?
Cn+H2n+2
Do alkanes have single or double bonds?
Single
What are the prefixes for alkanes?
- Meth 1
- Eth 2
- Prop 3
- But 4
In complete combustion are carbon and hydrogen oxidised or reduced?
Oxidised
In incomplete combustion what happens to carbon?
It is partially oxidised to carbon monoxide and carbion is released on its own as well as carbon particles or soot less energy is released in incomplete combustion that in complete combustion
What happens when sulfur dioxide dissolves in rainwater?
It forms an acidic solution, this is acid rain
How can the amount of acid rain be reduced?
- Removing sulfur from petrol, diesel, and fuel oil at the oil refinery before selling it
- Preventing sulfur dioxide from leaving power station chimneys (flue gas desulfurisation)
What is cracking?
A process carried out on fractions of oil after fractional distillation which involves breaking down larger alkanes into smaller more useful alkanes and alkenes
How does cracking work?
- Liquid paraffin is put on mineral wool, the porous pot catalyst and the paraffin is heated. The paraffin evaporates
- The paraffin vapour passes over the hot porous pot and the hydrocarbon molecules break down
- One of the products is ethene, this gas collects in the other tube
What did the earth’s early atmosphere consist of?
- Little or no oxygen
- A large amount of CO2
- Water vapour
- Small amounts of other gases
What is the evidence for the early atmosphere being how scientists think it is?
- The mixture of gases produced by volcanoes, gases from volcanic activity made up the early atmosphere
- The atmospheres of other planets in our solar system today, which have not been changed by living organisms
Why did carbon dioxide levels in the atmosphere decrease and oxygen levels increase?
- The earth cools and oceans are formed, carbon dioxide dissolves in the oceans
- Forms of life in the oceans evolve and photosynthesis begins, this causes oxygen to build up in the ocean and then the atmosphere
- The dissolved carbon dioxide is used by marine organisms to make calcium carbonate for shells, these shells fall to the sea bed and become part of the sediment once the organism has died
- Over millions of years the layers of sediment become squashed and form sedimentary rocks, this causes carbon dioxide levels in the atmosphere to decrease
What is the greenhouse effect?
Where greenhouse gases in the atmosphere absorb heat that is radiated from the earth, the greenhouse gases then release energy in all directions. This reduces the amount of heat radiated into space, keeping the earth warm
What are the effects of accumulation of greenhouse gases in the atmosphere?
- The greenhouse effect is increased meaning the global warming effect is increased
- Global warming is associated with long-term change to weather patterns (climate change) and rising sea levels due to melting ice
Give three examples of greenhouse gases and name their sources
- Carbon dioxide - burning fossil fuels
- Methane - livestock farming
- Water vapour (not a problem because excess water vapour leaves the atmosphere as rain and snow)
Which gases make up the Earth’s atmosphere today?
- Nitrogen (78%)
- Oxygen (21%)
- Other gases including argon water vapour and carbon dioxide (1%)
