The smallest partical of an element that retains the chemical identity of the element. I always think of an atom as a chemical in its smallest truest form possible.
A pure substance that can't be borken down in smaller substances by chemical or physical means. Some examples are diamonds, gold, aluminum, helium and oxygen; almost all metals are elements.
A substance that contains 2+ different elements chemically joined and that has the same composition throughout. A compound is consistent. Some Examples are propane, water, sugar, and vitamin C.
A mixture that is the same throughout (consistent). If you sample one homogeneous mixture you have sampled all of that one homogeneous mixture. Homogeneous mixtures are olive oil, brass, air, window cleaner etc.
A mixture in which different samples are not necessarily made up of the same proportions of matter; if something is clumpy it is clumpy as a whole is it hetero generous (like cookie dough). Examples are granite, salad, blood, and cookie dough.
select one here...