sentences: appearance is a kind of physical property & appearance is a kind of physical property -> disappearance is a physical public of odors appearance is a physical property of objects  disappearance is a physical public of odors & a rock is a kind of object -> appearance is a physical property of rocks appearance is a physical property of rocks  appearance is a physical property of rocks & classifying boiling appearance method by their type -> grouping rocks by their appearance is an example of classifying