Crude oil - long chain hydrocarbons that can be cracked by
thermal decomposition to form shorter chain alkanes
(Fuels) and alkenes (Polymers and Plastics).
Alkenes - Hydrocarbons, unsaturated:
contains a carbon - carbon double bond.
CnH2n
Hydrogenation
Vegetable oils are hardened by
reacting them with hydrogen gas
at 60oC. Uses a nickel catalyst.
E.g. Margarine - has a higher
melting point than oils.
Test for Alkenes
C1b Chemistry
Cracking of Hexane
Heat
Most polymers are nonbiodegradable and produced
from non-renewable crude oil.
Polymer Disposal:
Recycle to make other products
Burnt to generate heat - can
cause pollution.
Mixed with cellulose or starch to
make them biodegradable.
Ethene - polymerises to form poly(ethane):
also called polythene
Propene - polymerises to form poly(propene):
also called polypropylene
polymer
uses
polyethene
plastic bags and bottles
polypropene
crates and ropes
polychloroethene
water pipes and insulation
on electricity cables
If the plastic also has strong chemical bonds
between the polymer chains they are known as
Thermosetting Plastics
Polymers are made from small molecules called monomers
which are joined together to make long chains.
Process called Addition Polymerisation
Carbon - carbon double bonds in alkenes are broken allows carbon atom to join another carbon atom.
All examples of Thermosoftening
Plastics.
Weak intermolecular forces. Plastic
becomes soft on heating but hardens
again on cooling
Fats and oils can be saturated - single C-C bonds
Unsaturated fats and oils contain one
(monounsaturated) or more (polyunsaturated) C-C
double bonds.
Blood cholesterol levels can be lowered by eating
polyunsaturates and monounsaturates.
Two types of poly(ethane)
HDPE - High density,
LDPE - Low density
Both made from ethene but
under different conditions.
Food additives
Keep food fresher for longer
or make it appetising.
E numbers identify permitted
chemicals
- includes antioxidants;
colourings; emulsifiers;
stabilisers; gelling agents;
thickeners; flavourings;
preservatives; sweeteners
Water and oil form separate
layers - they are immiscible
Emulsions are formed when
tiny oil droplets are
suspended in water.
Emulsifiers stop oil droplets
and water from separating
out into layers.
Biofuels
Made from plant oils rapeseed oil and sunflower
oil.
Green fuels. - are
renewable
‘Greenhouse neutral’
Useful natural oils can be extracted from
plants.
Omega-3 fatty acids found in walnuts lower
fats in blood; reduce blood clots; lower blood
pressure and generally prevent heart disease.