crude oils and fuels Flashcards
what are crude oils
- finite resource found in rocks
- thick black oil used to make many everyday objects
- mixture of many compounds
- almost all compounds are hydrocarbons
what are hydrocarbons
a compound made entirely of hydrogen and carbon atoms
what are alkanes
compounds that consist entirely of single-bonded carbon and hydrogen atoms (saturated hydrocarbons)
- formula = C(n)H(2n+n)
what are fractions
substances in crude oil that similar boiling points
properties of alkanes
depends on amount of carbon atoms, as chain lengths increase alkanes become:
- more viscous
- less volatile
- less flammable
- boiling points increase
why do properties change based on chain lengths
large molecules have stronger intermolecular forces and become harder to separate
what is fractional distillation
a method of separating crude oil, boils and puts hydrocarbons of similar chain lengths into the same tray
method of fractional distillation
1) crude oil is vaporised and pumped into the bottom of a fractioning column (hot at bottom, cool at top)
2) the gasses rise and cool whilst doing so
3) when the temperatures drop enough they condense
4) the longest chains condense almost immediately and collect at the bottom, the short chains condense at lower temperatures and collect near the top
5) the liquid fractions are collected
examples of hydrocarbons with different chain lengths
long chains - tar, grease and lubricants
short chains - petrol
- short chains are more useful in everyday life but are less common to find in crude oil
what is cracking
a method to break long chains into smaller chains
different types of cracking
- catalytic
- steam
catalytic cracking
- catalysts known as zeolite (contains aluminium oxide and silicone oxide)
- zeolite catalysts are man made and expensive
- approximately 550 degrees
steam cracking
- heated over 800 degrees
- mixed with steam
- no catalyst needed, less expensive
what are alknenes
similar to alkanes but contain a carbon to carbon double bond, have less hydrogen atoms
- formula = C(n)H(2n)
what is combustion
the chemical name for burning hydrocarbons
- involves reacting with oxygen and releases large amounts of energy