Question

An unknown, clear liquid is given to you in a beaker. You transfer some of the liquid from the beaker to a clean, empty test tube, and begin to heat it. Soon, you observe a vapour leaving the top of the test tube. With further analysis you discover that the vapour is water vapour. Eventually, all that's left are a few crystals stuck to the sides of the test tube. Was the original liquid an element, a compound, or a mixture? Explain

Answer 1

A mixture because there was remaining  left at the bottom of the test tube and another substance that evaporated meaning that there was a lot more than one thing in the tube 

Answer 2

A mixture because there was residue left at the bottom of the test tube and another substance that evaporated meaning that there was more than one thing in the test tube.