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Chemistry – Unit 1
Atoms
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All substances are made of atoms
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There are around 100 different elements
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Name of particle
Proton
Neutron
Electron

Charge
+1
0
-1

 Atoms of each element are represented by a chemical symbol e
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 Atoms have a small nucleus, it is made of protons and neutrons, which
are surrounded by electrons
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 Atoms of a different element contain different numbers of protons
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 Elements in the same group have similar chemical properties
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 They need to be stored under oil to stop them from reacting with
oxygen and water vapour in the air
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Group 0
 Noble gases, they have 8 electrons in their
outer shell (except helium, which has 2)
 They are unreactive because they have a
stable arrangement of electrons

Chemical reactions
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When elements react, their atoms join together to create compounds
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Compounds formed by metals and non-metals are ions
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In molecules, atoms are held together by covalent bonds
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 Calcium carbonate can be
heated (thermal decomposition)
to from calcium oxide and
carbon dioxide
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 Limestone is damaged by acid
rain
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 Group 1 metals may not thermally decompose by the temperatures
reached by a Bunsen burner
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Limewater
 Limewater (calcium hydroxide) reacts with carbon dioxide to produce
calcium carbonate
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 Limestone is heated with clay to make cement
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 Cement is mixed with sand and aggregate to make concrete
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The
economics of extraction can change over time
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 Unreactive metals such as gold are found in the Earth itself
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The process of extraction
 Metals that are less reactive than carbon can be extracted from their
oxides by reduction (removal of oxygen) with carbon
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 Metals that are more reactive than carbon e
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 Electrolysis uses large amounts of energy and can therefore be
expensive
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 The copper can be purified by electrolysis
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 Copper is extracted from its ores using chemical processes that involve
heat or electricity
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New ways of extracting copper

 New ways are being found to extract
copper from low-grade ores to reduce
the environmental impacts of
traditional mining
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 Aluminium and titanium can’t be extracted from their oxides by
reduction with carbon
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Recycling metals
 We should recycle metals because we are extracting them from limited
resources and it is expensive in terms of energy and effects on the
environment
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The impurities
make it brittle so it has limited uses
 Blast furnace iron is used as cast iron because of its strength in
compression
 Most iron is converted into steels
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Alloys can be designed to specific
uses
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 Most metals in everyday uses are alloys
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Properties and uses of metals
 Metals in the centre of the periodic table are transition metals
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 They are useful for structural metals and for making things which must
allow heat or electricity to pass through them easily
 Copper has properties that make it useful for wiring and plumbing:
-it’s a good conductor of electricity and heat
-Can be bent but is hard enough to be used to make pipes or tanks
-does not react with water
 Low density and resistance to erosion makes aluminium and titanium
useful metals

Crude oil
 Is a mixture of a very large number of compounds
 Mixture – 2 or more elements that are not chemically combined
 The chemical properties of each substance in the mixture are unchanged
 It is possible to separate the substances in the mixture by physical
methods including distillation
 Most of the compounds in crude oil consist of molecules made up of
hydrogen and carbon (hydocarbons)
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 The many hydrocarbons in crude oil can be separated into fractions each
of which contains molecules with a similar number of carbon atoms

 The fractionating column works continuously, heated crude oil is piped
in at the bottom
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Trends in properties of hydrocarbons:
 Some properties of hydrocarbons depend on the size of their molecules
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 Shorter the molecules, the less viscous it is
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 The shorter the molecules, the lower the temperature at which that
fraction vaporises or condenses – and the lower its boiling point
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Hydrocarbon fuels
 Most fuels, including coal, contain carbon and/or hydrogen and may
also contain some sulfur
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Solid particles (particulates) may also be
released
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Here, solid particles of soot (carbons) and
unburnt fuel are released
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 The combustion of hydrocarbons releases energy
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Global impacts
 Sulfur dioxide and oxides of nitrogen cause acid rain, carbon dioxide
causes global warming, and solid particles cause global dimming
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Sulfur dioxide can be removed from the waste gases after
combustion, for example in power stations
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There are economic, environmental and ethical issues
surrounding their use
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This process involved heating the hydrocarbons to vaporise
them
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 The products of cracking include alkanes and unsaturated hydrocarbons
called alkenes
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 Unsaturated carbons can be represented in the following forms:
Double
bond

 Alkenes react with bromine water, turning it from orange to colourless
 Some of the products made from cracking are useful as fuels
Polymers
 Alkenes can be used to make polymers such as poly(ethane) and
poly(propene)
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For example:

USES OF POLYMERS:
Packaging materials
Dental polymers

Waterproof coatings for fabrics
Hydrogel wound dressings

Smart materials (shape memory
polymers)
 Many polymers are not biodegradable, which means they aren’t
broken down by microbes, this can lead to problems with waste
disposal
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Biodegradable plastics made from cornstarch have
been developed
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 Can be produced by fermentation with yeast, using renewable sources
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 The plant material is crushed and then the oil is removed by pressing,
like olive oil, or in some cases distillation, where water and other
impurities are removed, like sunflower oil
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They also provide us with nutrients
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This
produces quicker cooking and much different flavours but increases
the energy that is released when it is eaten
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 Emulsions are thicker than oil or water and have many uses depending
on their special properties
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 Emulsifier molecules have a hydrophilic head ‘water loving, oil hating’,
and a hydrophobic tails ‘water hating, oil loving’
 The hydrophilic head dissolves in water, and the hydrophobic tail
dissolves in oil, meaning that water and oil droplets can’t separate out
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 Unsaturated oils and double bonds are detected by bromine water, the
bromine water goes colourless when mixed when an unsaturated
vegetable oil
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 Hydrogen adds to the carbon–carbon double bonds
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The Earth’s crust
 The earth consists of a core, mantle and crust
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 The Earth’s crust and the upper part of the mantle are split into a
number of large pieces (tectonic plates)
 Convection currents within the Earth’s mantle driven by natural
radioactive processes cause the plates to move at relative speeds of a
few cm a year
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The Earth’s atmosphere



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