AQA GCSE · Question 04.4 · Bonding structure and the properties of matter
Pure gold is 24 carat. Suggest two reasons why silver and copper are mixed with gold to make 9 carat gold rings.
How to approach this question
1. Consider the properties of pure gold. It is a very soft metal. How would adding other metals change this?
2. Consider the cost of gold compared to silver and copper. How would adding cheaper metals affect the price of the final product?
3. You could also consider the effect on appearance (colour).
Full Answer
1. To make the gold harder/more durable.
2. To reduce the cost of the ring.
Pure gold (24 carat) is a very soft and malleable metal, which means it can be easily scratched, dented, or bent out of shape. Mixing it with other metals creates an alloy with improved properties.
1. **Hardness/Durability:** Adding metals like silver and copper disrupts the regular lattice structure of the pure gold, making it much harder and more resistant to wear and tear. This is essential for jewellery that is worn every day.
2. **Cost:** Gold is a very expensive precious metal. Silver and copper are significantly cheaper. By mixing them with gold, the overall amount of gold needed for the ring is reduced, making the final product much more affordable.
Common mistakes
✗ Stating it makes the ring "better" without specifying how (e.g., harder, cheaper).
✗ Suggesting it makes the ring heavier (while true, it's not a primary reason for making the alloy).
✗ Suggesting it prevents corrosion (gold is already very unreactive).
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