P4
Metals – Properties, Uses and Reactions
Metals are widely used in our industrialised society. This chapter investigates how
metals have used during history, the physical and chemical properties of metals and
their alloys. Extraction of metals from their ores and the recycling of metals are
important issues for modern society.
Alloys
Homogeneous mixture of a metal with one or more other
elements
An alloy is a solid solution
Common properties
of metals
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Electrical conductivity (ohm-1 or siemens (S))
Thermal conductivity (Js-1m-1K-1)
Hardness (measured on a relative scale 1 to 10)
Tensile strength (Nm-2 or Pa)
Resistance to corrosion (very high, high, moderate or
low)
Historical use of
metals
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Stone age
Copper age (3200 to 2300BC)
Bronze age (2300 to 700BC)
Iron age (700BC to 1 AD)
Modern age (1AD to present)
Balancing a chemical
equation
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Write a word equation to identify all the reactants and
products
Write the formulae for all reactants and products. Make
sure these formulae are correct and then do not change
the formula for any reactant or product.
Balance the equation by putting a number in front of
formula so that there is the same number of atoms of each
element on either side of the equation.
Add the symbols to describe the state of each reactant and
product ((s), (l), (g) and (aq))
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Mineral
A pure crystalline compound that occurs in the Earth’s crust
Ore
A compound or mixture of compounds from which a desired
substance can be economically extracted.
Extracting metals
from ores
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Smelting
A process for the extraction of a metal by heating substances
to produce molten material from which the metal can be
obtained
Mine the ore
Concentrate or purify the ore
Extract the metal
Purify the metal and/or make alloys
Extraction reactions
Most extraction reactions require the input of considerable
amounts of energy and this energy depends on the reactivity
of the metal being extracted.
Reactivity of metals
Metals display a wide range of reactivity with other
substances
 Oxygen
 Dilute acids
Chemical equations
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Neutral species equations
Zn(s) + 2HCl (aq)
Complete ionic equations
Zn(s) + 2H+(aq) + 2Cl-(aq)
Net ionic equations
Zn(s) + 2H+(aq)
ZnCl2(aq)
+
H2(g)
Zn2+(aq) + 2Cl-(aq) + H2(g)
Zn2+(aq) + H2(g)
Spectator ions
Ions that do not undergo any chemical change during the
reaction
Oxidation-reduction
reactions
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Oxidation
Loss of electrons
Reduction
Gain of electrons
Half-equations
Describe either the oxidation half-reaction or the reduction
half-reaction separately
Acids
Substances that produce hydrogen ions (H+)
Bases
Substances that either contain the oxide or hydroxide ion or
which produce the hydroxide ion when dissolved in water
Alkali
Soluble base
Activity series of
metals
List of metals from the most reactive to the least reactive
(K, Na, Li, Ba, Ca, Mg, Al, Zn, Fe, Sn, Pb, Cu, Ag, Pt, Au).
Electron transfer reactions
Also known as redox reactions
The activity of a metal depends on its ionisation energy.
The further to the right a metal is in the activity series the
more easily it can be extracted from its ores
Ionisation energy
The energy needed to remove an electron from a gaseous atom
of an element.
Factors affecting the
price of metals
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Abundance and location of the ores of the metal
Cost of extracting the metal from the ore
Cost of transporting the metal or its ores to the required
location
Steps in recycling a
metal
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Collect the used products
Transport the collected material to a central processing
plant
Separate the required substance from the impurities
Re-smelt the metal into ingots
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Advantages of
recycling of metals
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Less energy is used in recycling metals than in extracting
the metal from its ore
Finite natural resources (non-renewable resources) are
preserved
Less rubbish to be disposed of