C9 - Crude Oil and Fuels Flashcards
What is Crude Oil and what are its uses?
Crude Oil is a dark, smelly liquid formed over millions of years from the remains of plankton buried in mud under the sea.
It is a non-renewable resource used for fuel, plastics and other products.
What is Crude Oil a mixture of?
A MIXTURE of different carbon compounds - mostly hydrocarbons.
What is a hydrocarbon?
A hydrocarbon is a chemical compound that ONLY contains hydrogen and carbon atoms.
Why can Crude Oil straight from the ground not be used?
It contains too many substances with different boiling points.
What is Crude Oil separated into? What are they?
‘Fractions’ - substances with similar boiling points.
How is Crude Oil separated into fractions?
Fractional Distillation
What are most of the hydrocarbons in Crude Oil called?
Alkanes
What are Alkanes?
Alkanes are ‘saturated hydrocarbons’.
They contain as many hydrogen atoms as possible, and all the carbon-carbon bonds are single covalent bonds.
What do all named Alkanes end in?
‘ane’
What are the prefixes for the alkanes based on the number of carbon atoms within each molecule?
1 Carbon = Meth- 2 Carbons = Eth- 3 Carbons = Prop- 4 Carbons = But- 5 Carbons = Pent-
What are the names and formulae for the first 5 alkane molecules? What state are they in?
Methane - CH4 (g)
Ethane - C2H6 (g)
Propane - C3H8 (g)
Butane - C4H10 (g)
Pentane - C5H12 - (l) LIQUID
All are gases except pentane.
Based on the first 4 alkanes, what is the general formulae for an alkane?
CnH(2n+2)
Essentially, for every carbon atom, there are 2 times the hydrogen atoms, plus 2.
How can alkanes be visually represented?
Displayed formulae:
A diagram of all the single covalent bonds between the carbon-carbon bonds and the carbon-hydrogen bonds.
How can you work out whether a displayed formula (diagram) is an alkane?
You have to see of it fits the general formula:
1) Count the number of Carbon Atoms
2) Apply the (2n+2) rule for the Hydrogen Atoms.
3) Then count the number of Hydrogen Atoms and see if it matches the answer you calculated using the (2n+2) rule.
What is the aim of fractional distillation?
To separate crude oil into manageable fractions, each with similar boiling points.
What factor determines the properties of each fraction?
The size/length of the hydrocarbon molecule chains.
What sized hydrocarbons have a higher boiling point? Short or Long Chains.
Long chains - because there is more matter to boil.
What is the volatility of a substance?
Its tendency to turn into a gas.
What sized hydrocarbons have a greater volatility? Short or Long Chains.
Short chains - because they have a lower boiling point than longer-chain molecules.
*whence why you can smell petroleum gas (petrol) in the air - made out of short-chain molecules (pentane to decane)
What is the viscosity of a substance?
How easily it flows.
Low viscosity = runny
High viscosity = thick
What sized hydrocarbons have a greater viscosity? Short or Long Chains.
Long chains - because short chains have weak intermolecular forces (making it runny).
*whence why pentane (longer chain) is a liquid (stronger intermolecular forces).
What sized hydrocarbons have greater flammability? Short or Long Chains.
Short chains - because of the weak intermolecular forces between the molecules.
*whence why methane is a highly flammable gas.
Why do short-chain molecules make better fuels?
- They are more flammable - so easy to ignite.
- They are more volatile - because of their lower boiling point
What type of flames do short-chain molecules burn with?
A clean, unsmoky flame
