GCSE WJEC Chemistry- Crude oil

overall energy change is positive reaction is…

endothermic

overall energy change negative reaction is…

exothermic

overall energy change

total energy needed to break bonds MINUS energy released when new bonds form

bond energy

energy needed to break bond + energy released when bond forms

drawing exothermic reactions

put reactants higher than products

drawing endothermic reactions

put reactants lower than products

activation energy

min amount of energy required for a reaction

exothermic

heat released into surroundings

endothermic

heat absorbed from surroundings

fractions contain

mixtures of hydro-carbons (alkanes) with similar boiling points

crude oil

mixture of hydro-carbons that was formed over millions of years from marine organism remains

hydrogen fuel A

-only produces water as a byproduct

-renewable

alkanes bonding

every carbon atom has single bonds

alkene bonding

contains one double carbon bond → rest are single

methene

does not exist

alkene molecules are…

unsaturated + very reactive

alkane molecules are…

saturated + unreactive

hydrocarbon order

meth (many)

eth (elephants)

prop (pray)

but (but)

pent (praying)

hex (hurts)

alkene genreal formula

CnH2n

alkane genreal formula

CnH2n+2

Carbon dioxide fire extinguisher use + reason

electrical + chemical → takes away oxygen

hydrogen fuel D

-difficulty storing

-explosive

crude oil negatives

oil spills → ruin livelyhood

crude oil positives

-brings in money for government

-provides jobs

global warming effect

more extreme weather + more flooding

fractional distillation importance in daily lives

produces many useful products (plastic) + important source of fuels

bottom of fractional distillation qualities

-less flammable

-more viscous

-dark

-high boiling point

top of fractional distillation qualities

-more flammable

-less viscous

-light

-low boiling point

hydro-carbons

contains hydrogen and carbon atoms only

fire triangle

oxygen
fuel
heat

plastic D

• made from non-renewable resources

• creates pollution

• have to recycle

plastic A

• cheap

• durable

• many uses

isomers

same molecular formula but different structure

alkene bromine water reaction

decolourises bromine water

poly(ethene)

lightweight + waterproof → buckets + pipe

PVC

strong + light → window frames + doors

poly(propene)

tough + flexible → ropes + carpets

making polymers

before → monomer has double bond

after→ all single bonds poly (name)

PTFE

non-flammable + used as a non-stick surface in pans

cracking

breaking down large molecules into smaller more useful ones

What happens in polymerisation

double bond splits + molecules form chains

conditions needed for cracking

high temp + absence of air

butane isomer name

2-methylpropane

why alkenes de-colourise bromine water

bromine atoms attatch to molecules