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: