Alloys (Cambridge (CIE) IGCSE Chemistry)

Properties & uses of alloys

• An alloy is a mixture of a metal with other elements

  • Most alloys contain more than one metal 

  • Some alloys contain non-metals

Properties and uses of alloys

• Two examples of alloys are:

  • Brass - an alloy of copper and zinc and is much stronger than either metal

    • It is used in musical instruments, ornaments and door knobs

  • Stainless steel - an alloy of iron and other elements, for example, chromium, nickel and carbon

    • It is used in cutlery because of its hardness and resistance to corrosion / rusting 

• Other alloys include:

  • Iron with tungsten - extremely hard and resistant to high temperatures

  • Iron with chromium / nickel - resistant to corrosion

  • Aluminium with copper, manganese and silicon - the alloy is stronger but still has a low density, which makes it ideal for aircraft body production

• Alloys often have properties that are different to the metals they contain

  • For example, they can be:

    • Stronger

    • Harder

    • Resistant to corrosion / extreme temperatures

  • These enhanced properties can make alloys more useful than pure metals

The structure of an alloy

• Alloys have a different structure to metals

  • Metals have a regular arrangement of ions 

  • Alloys have an irregular arrangement of atoms 

The regular arrangement of a metal lattice structure is distorted in alloys

Explaining the properties of alloys

Extended tier only

• Alloys typically contain atoms of different sizes

• This distorts the normally regular arrangements of atoms in metals

  • The regular arrangement in a metal is layers of positive ions in a sea of delocalised electrons

• The distortion makes it more difficult for the layers to slide over each other

• So, alloys are usually harder / stronger than pure metals