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  • The world we live in is made of things,

  • billions and billions of different things,

  • like pickles

  • and pianos

  • and dump trucks

  • and octopi.

  • And even though these things seem totally different,

  • they're all made of the same stuff,

  • just combined in different ways.

  • To give you an idea of how this combining works,

  • let's take something apart.

  • Let's start with this bowl of macaroni salad.

  • If you were to reverse a recipe for macaroni salad,

  • you'll see it's made by mixing together

  • a bunch of ingredients,

  • like macaroni,

  • mayo,

  • vinegar,

  • vegetables,

  • and mustard.

  • This type of combining is called a mixture.

  • When you make a mixture,

  • you're combining two or more things together

  • without actually changing

  • the chemical identity of those things,

  • like mud, for example.

  • The soil and water in mud haven't actually changed.

  • They're still soil and water,

  • you've just created a mixture of soil and water,

  • mud.

  • It turns out that macaroni salad

  • is actually a mixture of mixtures

  • because many of the ingredients,

  • like mayo and mustard,

  • are already mixtures themselves,

  • which is nice for us

  • because if we look closely,

  • we'll the see the three main types of mixtures that exist.

  • The size of the particles in a mixture

  • determines the type of mixture.

  • On one end of the scale is a suspension,

  • like our muddy water example.

  • You get this if you take big chunks of something

  • and mix it with something else

  • so those chunks are just floating around.

  • Take runny mustard for example.

  • You'll see a bunch of little particles

  • like mustard seeds,

  • pepper,

  • allspice,

  • and minced shallots

  • all floating around in a liquid,

  • in this case vinegar and water.

  • This is called a suspension

  • because you've got particles of one thing

  • suspended in another.

  • Now, on the other end of the spectrum

  • is a solution.

  • The particles in this mixture are so small,

  • they are the actual molecules.

  • A solution is sort of like a suspension of molecules

  • where one type of molecule is blended

  • or dissolved with another.

  • Vinegar is an example of a solution

  • where the molecules of acetic acid

  • are blended with molecules of water.

  • The chemical properties of the molecules haven't changed,

  • they're just evenly mixed together now.

  • Saltwater and carbonated soda

  • are both examples of solutions

  • where other molecules are dissolved in water.

  • The last type of mixture is called a colloid,

  • which is somewhere between a suspension and a solution.

  • It's when you take two materials that don't dissolve

  • and you make the particles so small

  • that they can't separate.

  • Mayo is what happens

  • when you take oil and water,

  • which don't mix,

  • and you bind them together,

  • usually with the help of another substance

  • called an emulsifier.

  • In the case of mayo, it's lecithin, found in eggs.

  • And now, you are left with really small globs of oil

  • hanging out with really small droplets of water.

  • Whipped cream,

  • hairspray,

  • styrofoam,

  • and Jello

  • are all other examples of colloids.

  • So, let's get back to macaroni salad.

  • You've call colloids like mayo,

  • suspensions like mustard,

  • and solutions like vinegar,

  • but you've also got celery,

  • shallots,

  • and all other vegetable chunks

  • that are also part of the salad.

  • These aren't mixtures, really,

  • but we can break them up,

  • just like a TV can be broken up

  • into smaller and smaller complex component parts.

  • In the case of vegetables,

  • if you keep breaking things up,

  • they'll eventually end with thousands

  • of complex organic molecules,

  • things like ATP synthase

  • and RNA transcriptase

  • and water.

  • So now, once we've unblended all the solutions,

  • unmixed all the colloids,

  • separated all the suspensions,

  • and taken apart all of our vegetables,

  • we've reached the end of what we can unmix physically.

  • What we're left with is a whole bunch of molecules,

  • and these molecules remain chemically the same

  • whether they are by themselves

  • or thrown together in a salad.

  • If you want to separate these guys even further,

  • we need to unmix things chemically,

  • which means we need to start breaking some bonds.

The world we live in is made of things,

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B2 TED-Ed mixture salad macaroni mayo mustard

【TED-Ed】The science of macaroni salad: What's in a mixture? - Josh Kurz

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    阿多賓 posted on 2014/04/24
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