Properties of Metals Density – this is the mass of a substance in a given
volume. A high density material is much heavier than the same volume of
a low density material e.g. aluminium (low density) – used to build aircraft. Lead (high density) – is used as weights for fishing nets/lines.
Thermal Conductivity - metals all conduct heat well because of the close contact of the atoms. E.g. pots/pans.
Electrical Conductivity - metals all conduct electricity when solid and when molten because electrons can travel easily through the structure. E.g. cables
Malleability - metals can be beaten into different shapes. E.g. jewellery.
Strength - most metals are strong because of the metallic bond which holds the atoms together. E.g. bridges, cars, buildings etc.
Alloys
The properties of metals can be extended or altered by mixing them with other metals or with non-metals.
Iron can be changed into stainless steel by mixing it with small amounts of chromium. This stops the metal rusting.
Alloy Main
Metal
Other Element
s present
Uses Reason
Stainless steel
Iron Chromiu
m, Nickel Sinks, Cutlery
Non-rusting, strong
Mild steel
Iron Carbon Girders, Car
bodies Strong, rust resistant
Gold Gold Copper Rings, Electrical
contacts Good conductor,
unreactive
Solder Lead
(50%) Tin (50%)
Joining metals, electrical contacts
Low melting point, good conductor
Brass Coppe
r Zinc
Machine bearings,
ornaments
Hard wearing, attractive
Recycling Metals
Metals need to be recycled because they will not last forever (they are finite resources).
Reactions of Metalsa) With Water
Metal + Water Metal hydroxide + Hydrogen
E.g.Potassium + Water Potassium hydroxide + Hydrogen
K + H2O KOH + H2
Sodium + Water Sodium hydroxide + Hydrogen
Na + H2O NaOH + H2
Calcium + Water Calcium hydroxide + Hydrogen
Ca + H2O Ca(OH)2 + H2
Magnesium + Water Magnesium hydroxide + Hydrogen
Mg + H2O Mg(OH)2 + H2
Reactions of Metalsb) Metal Reacting with Acid
Metal + Acid A Salt + Hydrogen
E.g.Magnesium + Hydrochloric acid Magnesium chloride +
Hydrogen
Mg + HCl MgCl2 + H2
Reactions of Metals c) Metals reacting with oxygen
Oxygen can be made by heating potassium permanganate in a test tube and allowing the gas to pass through the preheated metal.
Metal + Oxygen Metal oxide E.g.
Magnesium + Oxygen Magnesium oxide
Mg + O2 MgO
Metal Ores
Ores are naturally-occuring compounds of metals from which metals can be extracted.
The three main types of ore are metal carbonates, metal oxide and metal sulphides.
Common Ores
Common name
Chemical name Metal
present
Haematite Iron oxide Iron
Bauxite Aluminium oxide Aluminium
Galena Lead sulphide Lead
Cinnabar Mercury sulphide Mercury
Malachite Copper(II) carbonate
Copper
Extracting Metals
Metals such as gold and silver occur uncombined on earth because they are unreactive and because of this these elements were among the first to be discovered.
Other metals, such as those in the table are found in compounds and have to be extracted (which is an example of reduction).
Extraction of Metals from Ores
The method used to extract a metal depends on the reactivity of the metal.
The more reactive the metal, the more difficult it is to extract.
The less reactive the metal, the easier it is to extract.
Methods of extraction a) Heating metal oxides
Silver oxide Silver + Oxygen
Ag2O Ag + O2
Few metals can be obtained in this way.
b) Heating Metal Oxides with Carbon
Metal oxide + Carbon Metal + Carbon dioxide
E.g. Iron oxide + Carbon Iron + Carbon dioxide
Fe2O3 + C Fe + CO2
This method is used to extract metals below aluminium in the reactivity series.
c) Using Electricity
Electricity can be used to split ionic compounds into their elements in a process called electrolysis.
The method is used to extract reactive metals above zinc in the reactivity series.
A large electric current is passed through the molten compound, and metal appears at the negative electrode.
d) Heating with Carbon Monoxide
Iron is extracted from its ore in the blast furnace by heating with carbon (coke) in the presence of air.
(Zone 1)
At the bottom of the furnace the reaction makes carbon dioxide
C + O2 CO2
(Zone 2)
Higher up, the carbon dioxide reacts with carbon to make carbon monoxide
CO2 + C CO
(Zone 3) Further up the carbon monoxide reacts with iron oxide to make iron and carbon dioxide
Fe2O3 + CO Fe + CO2
This is a reduction reaction.
Top Related