<Tr> <Td> Liquid </Td> <Td> Solution: amalgam (mercury in gold), hexane in paraffin wax </Td> <Td> Gel: agar, gelatin, silicagel, opal </Td> <Td> Wet sponge </Td> </Tr> <Tr> <Td> Solid </Td> <Td> Solution: alloys, plasticizers in plastics </Td> <Td> Solid sol: cranberry glass </Td> <Td> Clay, Silt, Sand, Gravel, Granite </Td> </Tr> <P> A heterogeneous mixture is a mixture of two or more chemical substances (elements or compounds). Examples are: mixtures of sand and water or sand and iron filings, a conglomerate rock, water and oil, a portion salad, trail mix, and concrete (not cement). A mixture of powdered silver metal and powdered gold metal would represent a heterogeneous mixture of two elements . </P> <P> Making a distinction between homogeneous and heterogeneous mixtures is a matter of the scale of sampling . On a coarse enough scale, any mixture can be said to be homogeneous, if the entire article is allowed to count as a "sample" of it . On a fine enough scale, any mixture can be said to be heterogeneous, because a sample could be as small as a single molecule . In practical terms, if the property of interest of the mixture is the same regardless of which sample of it is taken for the examination used, the mixture is homogeneous . </P>

A mixture that does not appear to be the same throughout is said to be