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- [Instructor] In a previous video,

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we used a particulate model like this

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to understand a reaction,

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not just to understand the reaction,

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but to balance the
chemical reaction as well.

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And when I hand drew these particles,

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the atoms in this particulate model here,

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I tried to draw it pretty close

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to their actual relative sizes.

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Carbon atoms are a little
bit bigger than oxygen atoms,

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and they're both a lot
bigger than hydrogen atoms.

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What we're gonna do in this video

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is extend our understanding
using a particulate model

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to start to visualize
what actually might go on

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in a mixture

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of some of these reactant molecules.

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So what I have here on the left-hand side

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are the various molecules.

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I have two methane molecules here.

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I have three water molecules.

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And what I wanna do with you

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is draw what we would expect
to see after the reaction.

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And I encourage you, like
always, pause this video

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and see if you can have a go at that,

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maybe with a pencil and paper,

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at least just try to
imagine it in your head,

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before I do this with you.

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All right, now, let's do this together.

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Now, we know that for every
methane and every water,

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we're going to produce one carbon monoxide

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and three molecular hydrogens.

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And each of those molecules of hydrogen

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have two hydrogens in them.

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So let's just say that this
one and this one react.

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They're going to produce
one carbon monoxide.

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I'm gonna try to draw the
relative sizes roughly, right?

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So one carbon monoxide.

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And then they're gonna
produce six hydrogen atoms

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that are going to be in
three hydrogen molecules.

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So let's do,

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that's two and four,

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and then I'll just do one here

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and then six.

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All right, so I took care
of this one and this one.

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And now we can imagine that
maybe this water molecule

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reacts with this methane molecule,

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and so that would produce
another carbon monoxide.

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Let me draw that

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roughly at the right size.

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Another carbon monoxide molecule

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and three more hydrogen molecules

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for a total of six more hydrogens.

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So that's one and two

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and three.

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And now we have this water right over here

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that had no one to react
with in this situation,

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had no partner.

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And so that's just going to be
a leftover reactant molecule.

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So let me just draw it right over here.

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So that water could be

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right over right over here.

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And so this was a useful way

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of starting to visualize
what might be going on.

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Remember, this is happening
at a very high temperature.

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They're all bouncing around, et cetera.

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And then when they react,
you might get this,

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but then this water molecule
has no one to react to,

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so it is, you could view it as a leftover

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after the reaction.