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In Chemistry, What Is a Heterogeneous Mixture?

Substances used in chemistry experiments.
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A heterogeneous mixture has different components that are distinctly visible and possess clearly identifiable separate properties with no blending of substances or traits. This can involve any combination of gasses, liquids, or solids, so long as no chemical transformation, alteration, or catalyst is present. The mixture requires no specific composition or ratio of ingredients for the various ingredients to retain their properties. Everyday examples include trail mix, air, or oil floating on the surface of water.

In chemistry, mixtures differ from compounds because they possesses no unique chemical properties caused by the combination of ingredients. Compounds create new chemical bonds when the ingredients are blended; mixtures may combine without altering the chemical properties of the substances, even if some characteristics may seem to differ. For instance, adding olives to a salad will create a heterogeneous mixture that may alter the flavor of the salad, but it doesn't alter the physical composition of the lettuce or dressing. The lettuce is still lettuce and not some other substance transformed by the olives.

A heterogeneous mixture differs from a homogenous mixture by the distribution of its materials. Its components are distributed unevenly, as opposed to an equal homogenous blend, with proportionate ratios of the ingredients present throughout.

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A particular type of mixture is the suspension, which involves solid particles of relatively large size suspended and distributed in a liquid or gas. When solids in a suspension begin to settle, the process is called sedimentation. Although for a time, the mixture may appear evenly distributed and wholly blended, over time, the suspension will always settle, with the heavier solid sinking below the suspension medium or to the bottom of a container.

Heterogeneous mixtures can be separated by simple processes of separation or filtration, such as separating wheat from chaff or straining noodles from water. Components with different densities can be separated by the process of flotation, in which lighter components rise while heavier ones sink. Filtration is used to separate mixtures containing at least one solid ingredient. Compounds, on the other hand, often require heating or some other chemical catalyst to trigger the reaction that would separate the ingredients.

The word "heterogeneous" itself originates from two Greek words. The first, heteros, means "different," and the second, genos, refers to a type or kind of thing. Together, they become "different thing," or a mixture of different things.

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titans62
Post 3

How would something like concrete be classified? I'm not sure of all of the things that go into the mixture, but I know gravel, sand, and water are big components. What I don't know is what substance holds everything together.

Is it possible to have something that is both part heterogeneous and part homogeneous? For example, you could theoretically use a microscope and separate every single rock and sand particle from a block of concrete, but wouldn't the water have chemically bonded with something else to the point where it couldn't be separated again?

Izzy78
Post 2

@stl156 - That's a very good idea. Personally I can't think of anything that would definitely disprove that.

Something your post did make me think of was salt water, though. It could potentially be an exception, but I'm not positive. If you mix salt with water, I'm pretty sure the molecules join together, but then if you boil salt water, the water will eventually evaporate and leave behind the salt.

What I'm not sure of, though, is whether the boiling counts as one of the triggers mentioned in the article. My other thought is that maybe the salt left over was just never able to bond with water. Does anyone else have thoughts about this?

stl156
Post 1

Obviously the opposite of a heterogeneous mixture would be a homogeneous mixture. I'm sure that would mean something where the two materials chemically interact to form a substance whose parts can't be separated again.

I think a good example of a homogeneous mixture that I have sitting in front of me might be soda pop. Once this ingredients are mixed, they can't be separated again. Maybe someone else can come up with better ones.

My thought from this is that maybe heterogeneous mixtures can be defined by saying no amount of mixing will ever make the parts inseparable. Would this be a valid idea, or are there some exceptions that I'm not thinking of?

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