Alloys (Edexcel GCSE Chemistry)

• Alloys are mixtures of metals, where the metals are mixed together physically but are not chemically combined
• They can also be made from metals mixed with nonmetals such as carbon
• Alloys often have properties that can be very different to the metals they contain, for example they can have greater strength, hardness or resistance to corrosion or extreme temperatures
• Alloys contain atoms of different sizes, which distorts the regular arrangements of atoms
• This makes it more difficult for the layers to slide over each other, so they are usually much harder than the pure metal
• Brass is a common example of an alloy which contains 70% copper and 30% zinc

Particle diagram showing a mixture of elements in an alloy. The different sizes of the two types of atoms prevent the layers of atoms from sliding over each other, so the alloy becomes less malleable than the pure metal

Steel Alloys

• Iron from a blast furnace is an alloy of 96% iron, with carbon, phosphorus, silicon and sulfur impurities
• It is called cast iron and is too brittle for many uses, so most of it is converted into steel by removing some of the impurities
• Not all of the carbon is removed as steel contains some carbon, the percentage of which depends on the use of the steel
• Alloys of steel are made from adding other metals to steel such as chromium, manganese or nickel
• By carefully controlling the amounts added, the particular type of alloy required can be produced
• Steel alloys are used in construction, transport, manufacturing and other industries

Steel Alloys & their Uses