Many metals in everyday use are alloys. Pure copper, gold, and aluminium are too soft for many uses and so are mixed with small amounts of similar metals to make them harder for everyday use.Bronze is a an alloy, that is a \"mixture\" of copper and tin.Mixtures are very interesting because they can dramatically change the properties of whenever ingredients are included (whatever is being mixed)Using an analogy, water will freeze at 32 degrees. Antifreeze will freeze at around 10 degrees. But if you mix them together, the mixture won\'t freeze until around -40 degrees.Answering your question, bronze is harder than copper because it is mixture of copper and tin unlike copper which is a pure metal...