Acids are reactive, with even weak acids like vinegar interacting with other materials to wow students. But strong acids can really put on a show. For example, aqua regia, or royal water, is a mixture of two strong acids -- hydrochloric and nitric acids- - that can dissolve gold, a noble metal. This reaction can be put to use. Watch as Reactions employs some acid know-how to explain a chemistry detective story to sort real gold from its imposters: https://youtu.be/cjN5yLvi_kA.