Economic importance of copper and zinc
Ancient bronze, modern cables and galvanized iron
1. Economic importance of the first transition series
2. The first metal
Ancient Egyptians made tools and statues of bronze thousands of years ago. What is bronze made of?
Pick the right answer
Predict: bronze is an alloy (a metal mixed with other elements) of copper and…
- A. tin
- B. zinc
- C. iron
Explanation
Bronze is an alloy of copper and tin: the book says copper-tin alloys are known as bronze.
3. 9- Copper
Copper is the first discovered metal. Copper-tin alloys are known as bronze. Copper is a good conductor of electricity, so it is used in electric cables and the coins industry.
- Copper → Bronze (copper + tin) (alloy with tin)
- Copper → Electric cables (good conductor)
- Copper → Coins
4. Fehling's solution
Fehling's solution is one of the copper compounds. It is used to detect glucose. Slide to add glucose and heat.
Glucose added (0 = no, 1 = yes) 0
5. Read the test
Pick the right answer
A student tests a sugar-free drink with Fehling's solution and heats it. It stays blue. What does that show?
- A. No glucose was detected
- B. Glucose is present
- C. The drink contains copper
Explanation
The test detected no glucose. Fehling's solution starts blue, and glucose changes the blue colour to orange; a solution that stays blue shows no glucose.
6. 10- Zinc: galvanizing
Remember: iron rusts in moist air.
Galvanizing
Coating other metals with zinc to protect them from rusting.
Zinc is used in galvanizing other metals to protect them from rusting. Think of the grey iron sheets on many rooftops.
- Iron (rusts in moist air) → Iron coated with zinc (galvanizing)
- Iron coated with zinc → Protected from rusting
7. Copper and zinc compounds
| Compound | Use |
|---|---|
| Copper II sulphate (CuSO4) | insecticide and fungicide, in the purification of water |
| Zinc oxide (ZnO) | manufacture of paints, rubber and cosmetics |
| Zinc sulphide (ZnS) | manufacture of illuminating paints and X-ray screens |
Remember: X-rays are invisible. A ZnS screen glows where they hit it, so we can see the picture.
8. Copper or zinc?
Sort into groups
Sort each use under the metal or its compounds.
Electric cablesDetecting glucoseInsecticide and fungicideGalvanizing ironX-ray screensPaints, rubber and cosmetics
Fill in the blanks
Bronze is an alloy of copper and _____.
Explanation
Bronze = copper + tin.
9. Summary
Back to the hook: ancient bronze is copper + tin.
- Cu: the first discovered metal; bronze = copper-tin alloys; cables and coins (good conductor).
- CuSO4: insecticide, fungicide, water purification. Fehling's: blue to orange with glucose.
- Zn: galvanizing other metals against rust.
- ZnO: paints, rubber, cosmetics. ZnS: illuminating paints and X-ray screens.
Can you explain why a Fehling's test that stays blue means no glucose?
Reveal
Fehling's solution starts blue, and glucose changes the blue colour to orange. If it stays blue, the colour did not change, so no glucose was detected.