Alloys and rust protection
Watch the whole lecture free
Make a free account to watch every lecture to the end: 1 worked example, 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
That was the teaching part. The rest of this lecture is free with an account: 1 worked example, 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
No password needed now: we email you a link to set one. Already have an account? Sign in, then come back to this page.
The teaching part (1 min) is free to watch. A free account opens the whole lecture: 1 worked example, 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Why not pure metals?
- What is an alloy?
- Why an alloy is stronger
Read the transcript of the teaching part
Last time
Before we start: last time, in The Periodic Table, Group I and the noble gases, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Why not pure metals?
Pure iron is soft and rusts. Pure copper bends easily. Yet the steel in a bridge is strong, and the brass in a trumpet keeps its shape. By mixing metals with other elements we make alloys, and by coating or sacrificing one metal we stop another from rusting.
What is an alloy?
An alloy is a mixture of a metal with one or more other elements. Often the other elements are also metals. It is a mixture, not a compound, so the elements are not chemically joined. Examples: brass is copper and zinc. Stainless steel is iron with chromium and nickel. Bronze is copper and tin.
Why an alloy is stronger
In a pure metal, the atoms are all the same size and are in regular layers. The layers can slide over each other when a force is applied, so the metal is soft and bends. In an alloy, the other atoms are a different size. They disrupt the layers, so the layers cannot slide easily. So the alloy is harder and stronger than the pure metal.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Alloys and their properties · Galvanising and sacrificial protection · Alloys and their properties.
Chapter 9: Metals
- The reactivity series 5 min
- Displacement reactions and extraction 5 min
- Extracting iron and aluminium 6 min
- Alloys and rust protection 5 min
Also for IGCSE Chemistry 0620
Which topics come up most in IGCSE Chemistry 0620 past papers, counted from every paper since 2004.