Reactivity of Metals
Place each of the different metal objects in a different container. At the same time, pour vinegar over each. Observe for bubbles.
The more hydrogen gas bubbles that are produced, the more reactive is the metal. Some metals react more easily than others. Iron rusts when it reacts with moisture in the air. Gold is suitable for jewellery because it is quite unreactive and doesnt tarnish.
Put the copper objects in the vinegar and leave it for a day. Observe the green corrosive coating. (You can try other metal objects in vinegar and see what colour their corrosive coating is.)
Test Household Cleaners on Corroded Metals
To test the cleaning ability of various household chemicals on metals, soak rusty nails, old coins particularly old copper coins and the like in various household chemicals such as Coke, household bleach (Use goggles and gloves with bleach) and sodium bicarbonate (also called bicarbonate of soda or baking soda). Leave these for a day and see how they performed.
You may be surprised at how well Coke can clean metals. After all, Coke does contain three different acids.