AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Pure metals are too soft for many uses and so are mixed with other metals…
Full specification wording
Properties of metals and alloys: Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder.
Pure metals have regular layers that slide easily, so they are often too soft for practical uses such as tools, aircraft parts or coins.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 4 of 5
Study notes
From the checked teaching notes for this specification point.
The idea
Pure metals have regular layers that slide easily, so they are often too soft for practical uses such as tools, aircraft parts or coins. To make a metal harder, it is mixed with one or more other metals to form an alloy. The atoms of the different metals have different sizes, so they disrupt the regular layered arrangement. This prevents the layers from sliding over each other as easily, making the alloy harder than the pure metal. For example, pure gold is very soft, but gold jewellery is usually alloyed with copper or silver to make it harder and more durable. Steel is an alloy of iron with carbon and sometimes other elements, and it is much harder than pure iron.
What earns the marks
- Pure metals are often too soft for many uses because their regular layers slide easily.
- An alloy is a mixture of a metal with one or more other elements, usually other metals.
- The atoms of the added element have a different size from the atoms of the main metal, which distorts the regular layers.
- Distorted layers cannot slide over each other as easily, so the alloy is harder than the pure metal.
- A correct example, such as steel being harder than pure iron or gold jewellery being alloyed for strength, supports the explanation.
Common mistakes and how to put them right
Saying that alloys are compounds of metals.
Put it right: Alloys are mixtures, so the elements are not chemically combined in fixed ratios.
Stating that alloying makes a metal softer.
Put it right: Different-sized atoms disrupt the layers and make the alloy harder.
Claiming that alloy atoms fit perfectly into the layers.
Put it right: Their different sizes distort the regular arrangement and prevent easy sliding.
Exam tips
- Define an alloy as a mixture before explaining how it changes properties.
- Use the idea of different-sized atoms disrupting layers as the key explanation for increased hardness.
- Give a named alloy and its use, such as steel in tools or gold alloy in jewellery, to show the link between property and purpose.
Try the lesson
The start of the Properties of metals and alloys: Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder. lesson, made from checked teaching notes for this specification point.
Have a go first
Why are pure metals often mixed with other metals to make alloys?
Listen
Pure metals have regular layers that slide easily, so they are often too soft for practical uses such as tools, aircraft parts or coins. To make a metal harder, it is mixed with one or more other metals to form an alloy. The atoms of the different metals have different sizes, so they disrupt the regular layered arrangement. This prevents the layers from sliding over each other as easily, making the alloy harder than the pure metal. For example, pure gold is very soft, but gold jewellery is usually alloyed with copper or silver to make it harder and more durable. Steel is an alloy of iron with carbon and sometimes other elements, and it is much harder than pure iron. A strong answer earns marks for these points. Pure metals are often too soft for many uses because their regular layers slide easily. An alloy is a mixture of a metal with one or more other elements, usually other metals. The atoms of the added element have a different size from the atoms of the main metal, which distorts the regular layers. Distorted layers cannot slide over each other as easily, so the alloy is harder than the pure metal. A common slip: Saying that alloys are compounds of metals. Instead, alloys are mixtures, so the elements are not chemically combined in fixed ratios. Exam tip: Define an alloy as a mixture before explaining how it changes properties.
See it
Put it in order
Put these steps in the order they happen.
- 1. Alloy is harder than the pure metal
- 2. Layers cannot slide as easily
- 3. Mix with other metals to make an alloy
- 4. Regular layers are distorted
- 5. Pure metal: regular layers slide easily
- 6. Pure metal is too soft for many uses
- 7. Added atoms have a different size
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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