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Narrative
A sample of high density polyethylene and a sample of low density polyethylene separate according to their densities.

Discussion
A sample of high density polyethylene cut in the shape of an "H" and low density polyethylene cut in the shape of an "L" are dropped into a cylinder containing a 1:1 mixture of ethanol and water. The high density polyethylene sinks and the low density polymer floats.

High density polyethylene is a linear polymer that has crystalline regions and is used to make rigid containers such as 1 gallon milk bottles. Low density polyethylene is a branched polymer whose molecules pack more loosely than those of high density polyethylene. Low density polyethylene is more transparent and waxy than the high density polymer and it is used to make flexible bottles and plastic wrap.