CC16 - fuels Flashcards
what is a hydrocarbon
a compound of only hydrogen and carbon
what is crude oil
natural resource a complex mixture of hydrocarbons
an important source of fuel and feedstock for petrochemical industry
why is crude oil a finite resource
takes so long to make it is being used faster than made and will one day run out
where does crude oil come from
formed underground at high temp and pressure over millions of years from plant and animal remains
what is crude oil made up of
lots of different hydrocarbons of different lengths
what can crude oil be separated into
fractions: simpler more useful mixtures containing hydrocarbons of similar lengths
what are the fractions of crude oil
- gases
- petrol
- kerosene
- diesel
- fuel oil
- bitumen
what is feedstock
raw materials
how are the fractions in crude oil separated
fractional distillation:
shorter hydrocarbons have lower boiling separate near top of column where it is cooler and vise versa
what are gases used for
domestic heating and cooking
what is petrol used for
fuel in cars
what is kerosene used for
fuel in planes
what is diesel used for
fuel in some cars and larger vehicles such as trains
what is fuel oil used for
fuel for large ships and some powerstations
what is bitumen used for
surface roads and roofs
what do the physical properties of crude oil depend on
how big the hydrocarbons in the fraction are
how does boiling point change in fractions of hydrocarbons
increases as hydrocarbon chains get longer. shorter chain have weaker intermolecular forces of attraction
how does ignition change in fractions of hydrocarbons
shorter chain hydrocarbons ignite easier
how does viscosity change in fractions of hydrocarbons
longer chain hydrocarbons are more viscous
how does colour change in fractions of hydrocarbons
longer chain hydrocarbons tend to be darker in colour
how many bonds does a carbon atom form
4
how many bonds does a hydrogen atom form
1
what is an alkane
single covalent bond between all carbon atoms (saturated)
formula: C(n)C(2n+2)
what is an alkene
have atleast one double covalent bond between carbon atoms (unsaturated)
formula: C(n)H(2n)
what is a homologous series
a series of compound that:
- same general formula
- differ by CH2 of neighbouring compounds
- similar chemical properties
- gradual variation of physical properties
what do oil fractions mostly contain
alkanes
what is complete combustion
reaction between hydrocarbon and O2
when theres a plentiful supply of oxygen
is an exothermic reaction
general formula for complete combustion
hydrocarbon + oxygen —-> carbon dioxide + water
when does incomplete combustion occur
limited supply of oxygen (in appliances such as boilers)
products of incomplete combustion
water, carbon dioxide, carbon monoxide, carbon (less O2)
problems of carbon monoxide
- colourless, odorless gas
- binds to haemoglobin in RBC limiting O2 in blood stream
- result in fainting, coma, even death
problems of carbon (incomplete combustion)
soot: blacken buildings, clog pipes, reduce air quality, cause breathing problems
acid rain
- sulfur impurities in hydrocarbons oxidise and form sulfur dioxide when burnt
- sulfur dioxide dissolves in water in clouds sulfuric acid that falls as acid rain
effects of acid rain
- corrodes metal and limestone weakening buildings
- damages crops, plants and trees
- kills fish (rivers and lakes too acidic to survive) and insects
oxides of nitrogen
- nitrogen and O2 from air react under high temperatures in car engines
effects of oxides of nitrogen
harmful pollutants
cause photochemical smog
air pollution: difficulty breathing, headaches
advantages of using hydrogen as a fuel
- only waste product is water
- renewable (obtained from water)
disadvantages of using hydrogen as a fuel
- hard to store
- not widley avaliable
- expensive to manufacture
- special, expensive engine required
what is cracking
taking a long chain hydrocarbon (alkane) and breaking it down into shorter more useful hydrocarbons (alkane and alkene)
what are the two types of cracking
thermal and catalytic
what is catalytic cracking
- use high temp and a catalyst
- catalyst speeds up the reaction
- covalent bonds break and reform
why are alkenes useful
- used to make polymers
- used as a starting material for useful chemicals
- useful as feedstock for petrochemical industry
thermal cracking
- uses high temperatures of up to 750°c
reasons for cracking
- shorter chain hydrocarbons more useful and in higher demand but in less supply
- longer chain hydrocarbon that there are more of in less demand can be cracked to meet supply of shorter chain hydrocarbons
