Alloys L.O: To know that most of the metals we use are alloys, and to know that copper, gold, aluminium and iron are made into alloys to make them harder. To understand that alloys can be designed to have certain properties and for a specific purpose. Wednesday, 19 September 2018

This pure iron has a regular arrangement of identical atoms. Purifying Iron ‘Iron' straight from the blast furnace is only about 96% iron. The other 4% is impurities such as carbon. This impure iron is used as cast iron. It can be poured into shapes, so it's handy for making ornamental railings. It can also be used for structures that need to withstand being compressed, for example in columns. But cast iron has limited other uses because the impurities that it contains make it brittle. To make the iron less brittle, the impurities are removed from most of the blast furnace iron to create pure iron. This pure iron has a regular arrangement of identical atoms. The layers of atoms can slide over each other which makes the iron soft and easily shaped. This iron is far too bendy for most uses, so most of it is converted into alloys.

Conversion of Iron to steel Most of the pure iron is changed into alloys called steels. Steels are formed by adding small amounts of carbon and sometimes other metals to the iron. There are several different types of steel. They have different uses because of their different properties.

Properties of Alloys FILL IN THE GAPS! Most metals in use today are actually alloys. Pure copper, gold, aluminium and iron are too soft for many uses so are made into alloys to make them more usable. Alloys are harder than pure metals because they are made from atoms of different elements. Different elements have different sized atoms. So when an element such as carbon is added to pure iron, the smaller carbon atoms will upset the layers of pure iron atoms, making it more difficult for them to slide over each other. ? ? ? ? ? ? ? ? ? ? ? iron harder usable layers slide soft sized pure alloys elements difficult

Properties of Alloys In the past, the development of alloys was by trial and error. But nowadays we understand much more about the properties of metals, so alloys can be designed to have particular properties that make them suitable for a specific purpose.

Common Alloys Here are some examples: Bronze: bronze is an alloy of copper and tin. It's harder than copper and it's good for making medals and statues from. Cupronickel: Cupronickel is an alloy of copper and nickel. It's hard and corrosion-resistant. It's used to make “silver” coins. Gold Alloys: Gold alloys are used to make jewellery as pure gold is too soft. Metals such as zinc, copper, silver, palladium and nickel are used to harden the “gold”. Aluminium Alloys: Aluminium alloys are used to make aircraft. Aluminium has a low density, but it's alloyed with small amounts of other metals to make it stronger.

Bronze Bronze is an alloy of copper and tin. It's harder than copper and it's good for making medals and statues from.

Cupronickel Cupronickel is an alloy of copper and nickel. It's hard and corrosion-resistant. It's used to make “silver” coins.

Gold alloys Gold alloys are used to make jewellery as pure gold is too soft. Metals such as zinc, copper, silver, palladium and nickel are used to harden the “gold”.

Aluminium Alloys Aluminium alloys are used to make aircraft. Aluminium has a low density, but it's alloyed with small amounts of other metals to make it stronger.

Questions – Fact Recall What percentage of iron does iron from a blast furnace contain? Why does cast iron have few uses? Why is pure iron easily bent? What element is added to iron to make steels? Name a type of steel that is resistant to corrosion. Why is pure aluminium made into an alloy? Name the metals that form these alloys: Bronze Cupronickel Why isn't pure gold used to make jewellery?

Questions - Application Many car parts, such as axles, need to be hard and rigid. Suggest a type of steel that could be used for this purpose. Steel containers are used in kitchens and laboratories. They need to be resistant to corrosion. Suggest a type of steel that could be used for these containers.

Answers – Fact recall About 96% It contains impurities that make it brittle In pure iron atoms are arranged regularly in layers that can slide over each other. This makes pure iron soft and bendy. Carbon Stainless steel As a pure metal it is too soft for many uses. a) Copper and tin b) Copper and nickel It’s too soft

Answers – Application High-carbon steel could be used (as it's a very hard, inflexible type of steel). Stainless steel could be used (as it is resistant to corrosion).