Properties of Metals and Alloys
Build confidence in Properties of Metals and Alloys for GCSE Chemistry with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Alloys are harder than pure metals because differently sized atoms distort the layers so they cannot slide over each other.
Free downloads
These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Metals have giant structures of atoms arranged in layers, with strong metallic bonding. Most metals therefore have high melting and boiling points.
Pure metals can be bent and shaped because the layers of atoms are all the same size and can slide over each other easily. This makes many pure metals too soft for practical use.
An alloy is a mixture of a metal with other elements. The different-sized atoms distort the layers, so they can no longer slide over each other easily. This makes alloys harder than pure metals, which is why most metals in everyday use are alloys rather than pure.
Revision notes
Properties of pure metals
Metals have giant structures with strong metallic bonding, so most have high melting and boiling points.
The layers of atoms are all the same size and can slide over each other easily, making pure metals soft and easy to bend or shape.
Why alloys are harder
An alloy is a mixture of a metal with one or more other elements.
The added atoms are a different size, which distorts the regular layers. The layers can no longer slide over each other easily, so the alloy is harder than the pure metal.
Conductivity
Metals are good conductors of heat and electricity because delocalised electrons are free to move through the structure.
They carry electrical charge and thermal energy, and this applies to alloys as well as pure metals.
Key points
- Metals have giant structures with metallic bonding.
- Most metals have high melting and boiling points.
- Layers of atoms in a pure metal slide over each other.
- Pure metals are therefore soft.
- An alloy is a mixture of a metal with other elements.
- Different-sized atoms distort the layers, making alloys harder.
Worked examples
Example 1
Explain why alloys are harder than pure metals. [3 marks]
Model answer
An alloy contains atoms of different sizes mixed with the metal atoms (1 mark). These distort the regular layers of atoms (1 mark), so the layers can no longer slide over each other easily and the alloy is harder (1 mark).
Example 2
Explain why pure copper is soft. [2 marks]
Model answer
The copper atoms are all the same size and are arranged in regular layers (1 mark), which can slide over each other easily when a force is applied (1 mark).
Example 3
Explain why metals have high melting points. [2 marks]
Model answer
Metals have giant structures with strong electrostatic attraction between the positive ions and delocalised electrons (1 mark), so a large amount of energy is needed to overcome this attraction (1 mark).
Common mistakes
Saying alloys are compounds.
An alloy is a mixture, not a compound.
Saying alloys are harder because they contain more atoms.
It is the different SIZE of the added atoms that distorts the layers.
Saying pure metals cannot conduct.
Both pure metals and alloys conduct because of delocalised electrons.
Forgetting to mention sliding layers.
It is the mechanism that explains both softness and malleability.
Exam tips
- Explain hardness through distorted layers and different-sized atoms.
- Use sliding layers to explain why pure metals are soft.
- Say alloy is a mixture, never a compound.
- Link conductivity to delocalised electrons.
Key terms
- Alloy
- A mixture of a metal with one or more other elements.
- Layers
- The regular arrangement of atoms in a metal structure.
- Metallic bonding
- Attraction between positive ions and delocalised electrons.
- Malleable
- Able to be bent or hammered into shape.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.