A student wants to make a metal salt. He decides he is going to use copper oxide and sulfuric acid as his starting materials, and adds 20 ml of acid to 2 g of the metal oxide. He finds that the solution makes the reaction happen faster. Eventually the reaction stops and there is still some copper oxide left, and notes that this must mean the copper oxide was added in . He also notes that the solution has now turned blue, and starts to filter off the remaining solid. To get the salt out of solution he needs to the water off, and sets up his equipment. He decides to only remove a small amount of water, and leave it to crystallise out over night. When he comes back in the morning he finds lovely blue crystals of copper .

+ metal → salt + water + carbon dioxide