Uses of metals and alloys including magnalium and brass Revision Notes | GCSE Edexcel Higher Chemistry

1. Why Alloys Rule the World

Look around you right now. That spoon in your kitchen? It's not pure iron. Your bike frame? Not pure aluminium. The coins in your pocket? Definitely not pure copper. Here's the thing that catches most students off guard: most metals in everyday use are alloys, not pure metals.

Pure metals have a problem. They're often too soft, too weak, or too reactive for real-world jobs. Iron rusts. Pure gold bends like butter. Aluminium corrodes. But mix them with other elements, and suddenly you get materials that can build skyscrapers, survive space missions, and last for decades.

2. The Copper Champions: Bronze and Brass

Copper was one of the first metals humans used, but pure copper has limitations. It's soft and not particularly strong. Ancient metalworkers discovered that mixing copper with other metals created superior materials.

Bronze revolutionised human civilisation so much that we named an entire historical period after it. It's harder than pure copper and doesn't corrode as easily. Brass, meanwhile, looks like gold but costs far less, making it perfect for decorative applications and musical instruments like trumpets and saxophones.

3. Gold Alloys and Their Properties

Gold jewellery is often made as an alloy with other metals to make it harder and more durable.

Adding other metals makes gold harder and more durable.

Worked example: Calculating Gold Percentage in Jewellery

Why are gold alloys harder than pure gold? [2 marks]

1. 24 carat = 100% gold — This is the definition of the carat system
2. $\frac{9}{24} = \frac{x}{100}$ — Other metals make gold harder and more durable
3. $x = \frac{9 \times 100}{24} = \frac{900}{24} = 37.5$ — [1 mark for method, 1 mark for answer]

Answer: 37.5% gold

The other metals in gold alloys aren't just fillers. Copper gives gold a reddish tint (rose gold), while white gold is usually made by alloying gold with metals such as nickel or palladium. These additions also make the jewellery much more resistant to scratching and bending.

4. Steel: The Ultimate Alloy Family

Steel isn't just one alloy - it's a whole family. All steels are alloys of iron containing specific amounts of carbon and other metals. But here's where it gets interesting: tiny changes in carbon content create dramatically different materials.

Think of carbon atoms like tiny reinforcement bars in the iron structure. A few carbon atoms make the steel stronger. Too many, and the steel becomes brittle - strong but likely to snap under stress.

But the steel story doesn't end with carbon. Add chromium and nickel, and you get stainless steel - hard and resistant to corrosion. This is why your kitchen sink doesn't rust, even though it's made of iron-based steel.

5. Aluminium Alloys: Light but Mighty

Pure aluminium has one amazing property: it's incredibly light. But it also has a problem - it's not particularly strong. Aluminium alloys solve this by mixing aluminium with small amounts of other metals like copper, magnesium, or silicon.

The result? Materials that are still low density but much stronger. This combination of lightness and strength makes aluminium alloys perfect for aircraft, where every kilogram matters. A Boeing 747 is about 80% aluminium alloy.

6. Exam Mastery: Alloys in the Test

Examiners love testing alloys because they combine chemistry knowledge with real-world applications. Here's how to nail these questions every time.

Remember the examiner's favourite trick: they'll give you a scenario and ask you to suggest the best alloy. Always justify your choice by linking the alloy's properties to the job requirements. 'Bronze for ship propellers because it's corrosion resistant in seawater' wins more marks than just 'bronze'.