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And then the other thing I
didn't get to do on Monday

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was my Why This Matters,
and so I want to do that.

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Now hair is very much affected
by the softness of water.

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But instead of me showing
you lots of pictures of hair

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that I found randomly on the
internet, googling soft water,

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hard water, different
forms of water, hair,

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I'm showing you pipes, because
that's much more actually

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relevant in terms of like, for
example, whether you can get

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water into your house at all.

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All right?

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And this is a real problem.

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If you have hard
water what it means

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is you've got
minerals in the water.

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Right?

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Things like magnesium and
calcium ions are in the water.

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And what happens is, if you run
that through pipes, they tend

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to react and form and deposit.

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And you get these deposits
of very, very hard mineral

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deposits around the edges that
eventually look like this.

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That's not a good thing.

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And so you need to soften the
water, and that's something

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you may have heard of.

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But now you really know how
to think about it, because you

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can think about it in
terms of all of the things

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that you've learned.

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And just as an example,
if one of those minerals

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that's a problem is calcium--

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oh, it is, right?

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Magnesium is another one
that can cause this in pipes.

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You've got to somehow
take it out of the water

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or at least make it into a form
that makes it like insoluble,

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so it'll just flow, and
it won't have a chance

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to come around and deposit on
the edge there of the pipe.

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And so what do you do?

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Well, you add, for example--

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oh, we've done this before.

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Right?

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What if I add soda,
something called soda ash?

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Oh, we know what that is.

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That's Na2CO3, and that
will give me some ions.

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It'll give me some
Na pluses, and it'll

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give me some CO3 2 minuses,
and those are in aqueous.

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Now, this is all
part of the stuff

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that we've been talking about.

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You're dissociating this
to get ions in solution,

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but why do I want these ions?

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That's a water softener.

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Why?

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Because now you can see it.

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Right?

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Because this one
here, this one here

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is going to remove the calcium.

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So if I've got these
calcium, these minerals,

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in the water making it hard
water which leads to that

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and wreaks havoc on
your hair, then you

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get a little of this
in there, and you're

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going to react with the calcium.

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Why?

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It's because of
what we already saw.

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If I have this--

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this is something we've already
looked at-- if I have calcium 2

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plus, and I have some
bicarbonate in there,

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CO3 minus, then we know that
I can get precipitates, Ca--

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this is just what we looked
at in the goody bag, right--

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plus CO2 plus H2O.

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That's the same kind of reaction
that we looked at already.

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We have calcium carbonate,
calcium carbonate.

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Why?

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Well, because this is
going to give me these.

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This is a source for those
which then eats up some calcium.

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And you think, well, now this
can take the calcium ions out,

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so that it runs through.

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That's what you want to do here.

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That's how you soften water.

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Well, you can add lime which
gives me a source of OH minus,

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and that takes
out the magnesium.

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And these are ways to change
the chemistry of water,

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so that you don't have
as many ions, mineral,

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these calcium and magnesium
ions floating around that cause

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problems.