P9
Energy and its Traditional Sources
People in industrialised societies use large amounts of energy. This chapter
investigates why this energy is needed, how it is used and the present and future
sources of our energy.
Why humans need
energy
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Keep their bodies functioning
Obtain food to keep warm
Travel
Transport of goods
Construction
Appliances for home
Health facilities
Food processing
Commerce and industry
Energy use in
Australia
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Manufacturing (27%)
Transport (25%)
Domestic (15%)
Agriculture, mining and construction (7%)
Electricity generation (excluding domestic) (20%)
Other (6%)
Sources of energy in
Australia
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Coal (40%)
Crude oil (36%)
Natural gas (18%)
Wood and bagasse (4%)
Hydroelectricity (2%)
Bagasse
Fibrous waste from sugar cane after the sugar has been
extracted.
Fossil fuels
Substances formed by the action of high temperature and high
pressure on decaying plant and animal matter over millions of
years. (Coal, crude oil, oil shales, tar sands and natural gas)
Photosynthesis
Process in which plants use solar energy to convert carbon
dioxide and water into carbohydrates (glucose) and oxygen.
6CO2(g) + 6H2O(l) + energy
C6H12O6(aq) + 6O2(g)
Photosynthesis is an endothermic reaction.
Respiration
Respiration occurs in the cells of living organisms and
involves the release of the energy stored in substances such as
carbohydrates.
C6H12O6(aq) + 6O2(g)
6CO2(g) + 6H2O(l) + energy
Allotropes
Forms of the same element in the same physical state that
have distinctly different properties.
The atoms in allotropes are joined or packed together
differently to form molecules or crystals.
Allotropes of carbon
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Diamond
Graphite
Buckminsterfullerene
Covalent bonds
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Single bond that shares 2 electrons
Double bond that shares 4 electrons
Triple bond that shares 6 electrons
Electron-dot
structures
Show valence electrons and how they combine to form
chemical bonds
Structural formulae
Show how atoms are joined to each other in molecules by
using dashes to indicate bonding pairs of electrons.
Condensed structural
formulae
These are intermediate between molecular formulae and
structural formulae and show some of the bonding (carboncarbon bonds) but not all (carbon-hydrogen bonds)
CH3-CH=CH2
Isomers
Different compounds with the same molecular formula but
different structural formulae
Molecular models
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Space-filling models that give the best description of the
physical appearance of the molecule.
Ball-and-stick models that use the balls to represent the
position of the nuclei of atoms and sticks to indicate the
type and geometry of the bonding.
Hydrocarbons
Compounds that contain atoms of the elements carbon and
hydrogen only. Different types of hydrocarbons include
 Straight-chain hydrocarbons
 Branched chain hydrocarbons
 Cyclic hydrocarbons
 Aromatic hydrocarbons
Fractional distillation
Process used to separate crude petroleum into different
products that consist of hydrocarbon compounds with similar
boiling points and number of carbon atoms in their molecules.
Homologous series
A family of compounds that can be represented by one general
molecular formula
Alkanes
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Hydrocarbons that contain only single bonds
Saturated
General formula CnH2n + 2
Naming
hydrocarbons
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The systematic name for each hydrocarbon consists of a
stem that indicates the number of carbon atoms in the
molecule and a suffix that indicates the family to which
the compound belongs.
The stems for hydrocarbons with up to eight carbon
atoms are
o Meth- 1 carbon
o Eth2 carbons
o Prop- 3 carbons
o But4 carbons
o Pent- 5 carbons
o Hex- 6 carbons
o Hept- 7 carbons
o Oct8 carbons
The group endings for the three homologous series of
hydrocarbons are
o Alkanes -ane
o Alkenes -ene
o Alkynes -yne
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Alkenes
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Naming alkenes
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Alkynes
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Hydrocarbons that contain one double carbon-carbon
bond
Unsaturated
General formula CnH2n
Take the usual stem name to denote the number of carbon
atoms in the chain and then add the ending –ene.
Show the location of the double bond by putting in front
of the name the number of the carbon atom at which the
double bond starts
Begin the numbering of the carbon chain from the end of
the molecule that minimises the number of the double
bond.
Hydrocarbons that contain one triple carbon-carbon bond
Unsaturated
General formula CnH2n – 2
Naming alkynes
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Physical properties of
hydrocarbons
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Take the usual stem name to denote the number of carbon
atoms in the chain and then add the ending –yne.
Show the location of the triple bond by putting in front of
the name the number of the carbon atom at which the
triple bond starts
Begin the numbering of the carbon chain from the end of
the molecule that minimises the number of the triple
bond.
Non-polar molecules
Dispersion forces increase with increasing molecular
weight
Low melting and boiling points that increase with
increasing molecular weight
Volatility decreases with increasing molecular weight
Insoluble in polar solvents such as water but soluble in
non-polar solvents.
Functional group
Centre of reactivity of a carbon compound.
All molecules with the same functional group react very
similarly regardless of which carbon-hydrogen chains are
attached.
Safety precautions
when using
hydrocarbons
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Well-maintained cylinders and fittings for gaseous
hydrocarbons
Added odours for early detection of leaks
Sturdy containers for liquids
Minimise the quantities in daily use
Do not handle these liquids in confined spaces
Keep away from naked flames
Used fume hoods for prolonged use
Keep areas well ventilated and avoid inhaling the fumes.