For each of the following descriptions, decide if the material is likely to be a mixture or a pure compound or element, and then decide if the process is a chemical or a physical change. a) A clear, colorless, crystalline solid is heated. A pale yellow-green gas is given off and a shiny, malleable metal was left behind. b) A brown liquid is heated and a colorless, aromatic liquid is produced along with a clear, colorless liquid while a brown liquid is left behind in the container. c) Adding sugar to tea causes the tea to taste sweeter. d) A shiny, dark gray metal and a clear colorless gas combine to form a flaky orange solid.