Unlike sugar or salt, copper won't dissolve when you stick it in water. Sulphuric acid and nitric acid, however, are strong enough they can oxidise copper. Either acid will do the trick, although it will release noxious fumes in the process, so you should only attempt this procedure in a lab setting. As long as you take the appropriate precautions, however, this procedure can make an interesting experiment and a demonstration of an oxidation-reduction reaction.
Don your goggles, gloves and coat. Perform this procedure under the fume hood for safety.
Place the copper strip in the beaker and add a little water -- just enough to cover it.
Add 10 drops of the nitric acid solution and watch to see what happens. Add more nitric acid as needed.
The brown gas you'll see rising from the solution is nitrogen dioxide, a major environmental pollutant also produced by emissions from cars.