C9.1 - C9.4 Crude Oils And fuels✔️ Flashcards
Describe how crude oil is made?
Crude oil was formed over millions of years from the remains of tiny, ancient sea animals and plants, mainly plankton, that were buried in mud - over time, layer upon layer of rock was laid down on top creating high pressure and temperature and in the absence of oxygen made crude oil
What is a mixture?
A mixture contains two or more elements or compounds that are not chemically combined together - nearly all of the compounds in crude oil are compounds containing only hydrogen and caron atom these are called hydrocarons
What are alkanes?
Saturated hydrocarbons - all the carbon-carbon bonds are single covalent bonds containing the maxium amount of hydrogen atoms possible in each molecule so no more hydrogen atoms can be added - general formula is Cₙ H₂ₙ₊₂
How is crude oil seperated?
seperated into hydrocarbons with similar boiling points called fractions through the process of fractional distillation - each hydrocarbon fraction contains molecules with similar numers of carbon atoms
Describe the process of fractional distilation to seperate crude oil?
Crude oil is heated and fed into the bottom of a fractionating column as hot vapour (column is kept as hot at bottom and cooler at top) - gases move up the column and the hydrocarbons condense when they reach the temperature - different fractions are collected at different levels - once collected the fractions need more processing before they can be used
How are hydrocarbons with the lowest boiling points collected?
They are the hydrocarbons with the smallest molecules and are piped out of the cooler top of the column as gases
How are hydrocarbons with the highest boiling points collected?
At the bottom of the column, the fractions have high boiling points - they cool to form very thick liquids or solids at room temperature which are collected
Why are lighter fractions of crude oils useful?
Useful as fuels because they ignite more easily and burn well with cleaner (less smoky) flames
What happens when hydrocarbons burn in plenty of air?
They transfer lots of energy to the surrondings - and the carbon and hydrogen in the fuel are completely oxidised - to produce carbon dioxide and water
What are the products of complete combustion of a hydrocabon?
Carbon dioxide and water
What are the products of incomplete combustion of a hydrocabon?
Instead of all the carbon in the fuel turning into carbon dioxide - carbon monoxide gas is also formed which is a toxic gass which is colourless and odourles
What is cracking?
The process in which larger less useful hydrocarbon molecules can be broken down into smaller, more useful ones
Dsecribe how the process cracking takes place?
Takes place at an oil refinery in steel vessels called crackers - in the cracker a heavy fraction distilled from crude oil is heated to vaporise the hydrocarbons - the vapour is then either passed over a hot catalyst or mixed with steam and heated to a very high temperature
What does cracking produce?
Saturated hydrocarbons used as fuels and unsaturated hydrocarbons (called alkenes)
How do unsaturated hydrocarbons (Alkenes) react with orange bromine water?
A positive test for a unstaurated hydrocarbon is that it turns orange bromine water colourless
