Though not totally relevant to this site's theme, it s important to know the difference between compounds and mixtures.
Compound: A compound is the bond of two chemical elements together at a fixed ratio. You can only separate compounds by chemical means (i.e. not mechanical, a chemical reaction). All compounds are homogeneous.
Mixture: A mixture can be separated using mechanical means (freezing, filtering, distilling, etc.) and does not have a fixed ratio of parts. When a mixture is formed there is no energy exchange (no chemical reaction) and the components of a mixture don't change properties. Mixtures can be homogeneous or heterogeneous (uniform or nonuniform). A mixture can also include compounds, as long as they are not all bound to each other (like air: nitrogen [diatomic element], oxygen [diatomic element], water vapor [compound], and even bits of argon gas [element]).
Pure element: Any element that is on the periodic table (this is indivisible, sort of nuclear disintegration). Some elements* are diatomic, meaning that they naturally occur in groups of two of the same element linked together (like the oxygen we breath, O subscript 2). These diatomic elements are both elements and molecules. All elements are homogeneous.
*These elements are Hydrogen, Nitrogen, Florine, Oxygen, Iodine, Chlorine, and Bromine which can be remembered by the mnemonic device Have No Fear of Ice Cold Beer (or Beverages, if you are in an academic setting). These can also be remembered by the fact that six of the diatomic elements (N, O, F, I, C, and Br) form a seven when all are highlighted on the periodic table, reminding you to include hydrogen as the final diatomic element.
Try your luck with these "Flash Cards": try to guess what is a compound and what is a mixture and what is a pure element. You can hit play and the slide will change every five seconds on it's own, or you can just click the forward button at your own pace.
Compound: A compound is the bond of two chemical elements together at a fixed ratio. You can only separate compounds by chemical means (i.e. not mechanical, a chemical reaction). All compounds are homogeneous.
Mixture: A mixture can be separated using mechanical means (freezing, filtering, distilling, etc.) and does not have a fixed ratio of parts. When a mixture is formed there is no energy exchange (no chemical reaction) and the components of a mixture don't change properties. Mixtures can be homogeneous or heterogeneous (uniform or nonuniform). A mixture can also include compounds, as long as they are not all bound to each other (like air: nitrogen [diatomic element], oxygen [diatomic element], water vapor [compound], and even bits of argon gas [element]).
Pure element: Any element that is on the periodic table (this is indivisible, sort of nuclear disintegration). Some elements* are diatomic, meaning that they naturally occur in groups of two of the same element linked together (like the oxygen we breath, O subscript 2). These diatomic elements are both elements and molecules. All elements are homogeneous.
*These elements are Hydrogen, Nitrogen, Florine, Oxygen, Iodine, Chlorine, and Bromine which can be remembered by the mnemonic device Have No Fear of Ice Cold Beer (or Beverages, if you are in an academic setting). These can also be remembered by the fact that six of the diatomic elements (N, O, F, I, C, and Br) form a seven when all are highlighted on the periodic table, reminding you to include hydrogen as the final diatomic element.
Try your luck with these "Flash Cards": try to guess what is a compound and what is a mixture and what is a pure element. You can hit play and the slide will change every five seconds on it's own, or you can just click the forward button at your own pace.