During a visit to a heritage museum, a group of students observed several metal objects displayed in different galleries.
- A gold necklace looked as bright as a newly made ornament even though it was many years old.
- An old copper vessel had developed a green coating on its surface.
- A silver plate displayed a black coating, making it appear dull.
- An aluminium window frame showed no visible damage even after years of exposure to air and rain.
- The museum guide explained that different metals react differently when exposed to air and water. Some metals undergo changes on their surface, while others remain almost unchanged.
Study the case carefully and answer the following questions.
1. Which metal mentioned in the case is most suitable for making jewellery because it retains its shine?
2. What caused the green coating on the copper vessel? -
3. Why did the aluminium window frame remain in good condition? -
4. Which conclusion can be drawn from the museum observations? -