Imagine that you are living in Europe in the Middle Ages. You have been summoned by the king of your land to help in a very important matter. Someone has stolen the king's solid gold crown! The king has issued a proclamation offering a reward of 500 gold coins for the safe return of his crown. The problem is that the king has received 5 crowns that appear to be made of pure gold and look identical to the missing crown. Your job is to correctly identify the gold crown, and persuade the King why your identification is scientifically accurate.