In these materials you can see pockets of one material or another. At some level it becomes very difficult to make the distinction between homogenous and heterogeneous. To the naked eye a mixture can be homogenous, but upon magnification it will be heterogeneous. At the atomic and molecular level, all matter is heterogeneous. Mixtures are created and uncreated by physical methods.
All elements have a symbol, usually related to their English names.
Compounds A compound is two or more elements, always in the same proportion. This means that for any sample of pure sodium bicarbonate, the fraction 0.274 of the mass of that sample is sodium, and 0.012 of the mass of the sample is hydrogen, etc. Exact equivalence statements are statements that are true for all time in all places. They also specify two ways of saying the same thing. A special sense equivalence statement may be true for all time, but the two materials which are related are not really the same things.