Three, two, one go!
I've been joined today by Peter and my friend Rachel as well, and they're going
to help me demonstrate some equilibrium ideas for a quick lesson here. We've got
some tubs of water. Would you agree that they're roughly the same? I think
this may be a little bit more on this one shall I even it up? You can tip a
little bit up perhaps, it doesn't really matter. Ok, so are you ing agreement that we've got
about the same amount in each one? Ok so the job here is to try and fill up
the other person's tub. So what do you think's going to happen Rachel?
I think Peter's going to get wet. Ok, and Peter? Because I think you're quite
competitive. Yeah I think Rachel's in for a surprise. Ok, all right,
so we'll give it a couple of about 30 seconds or so and we'll see how we
get on. Ok, phones are out of the way. The objective is of course to try and
get your water in there, not on the floor if possible, okay.
Can we agree to stay on different sides of the tubs? Ok, so the
objective is not to empty your tub but to fill the others up.
So three, two, one go.
Ok, we'll hit pause hit. No cheating!
So what's happened? We've got wet and I think, it doesn't look as if there's
a very significant difference, maybe a little bit more there.
Would you agree? Yes. So we've got about the same amount of water in
each tub. Now, as we've gone here, okay, the level of the liquid has kind of remained
the same. But we're discussing this idea of equilibrium the idea that on a
macroscopic scale over a long period of time we've seen the levels of the
liquids. These are representing chemicals in the reaction so we could have
chemical A reacting to form chemical B but chemical B can react to form
chemical A in the backwards reaction. So over a period of time if we reached a
situation where you guys are both going at the same, potentially at the same
speeds, the levels of the liquids are not going to change. Happy with that?
So let's imagine for example just to finish up with that these are
actually representing the the amounts of a blue and a red chemical in a flask. So
this is our blue chemical, this is a red chemical. If we had a 50/50 mixture what
colour would it appear? Purple?
Now the only proviso or caveat we might put on
this is the fact that the floors a little bit wet here. So what would
happen over a long period of time if we were to continue this? We'd lose both of the
agents that are causing the reaction. Essentially. So we can only reach
equilibrium if all of the water remains the same or all of our chemicals are
kept in. We call that a closed system. So what we're going to do now is going to
play with the system a little bit. Maybe I think I want to be mean to Peter so
we're going to switch things up a little bit, and Peter I'm going swap you
for this. So we're changing essentially the conditions of our
equilibrium that we're going to set up. So Rachel what's going to happen next?
I'm going to win. You're going to say you're going to fill up his tub. Would
you agree? I hope so. Okay. So yeah so basically when you're done we'll
know that we're done because your tub will be empty, yes? Okay. So if
I shout pause again that is a good reason. Don't trip over the wire.
Three, two, one, go.
Keep going. Rachel's filling up here.
Closed system, try and keep it in the tubs.
You guys are so much worse behaved than students are.
No, that's cheating. We're going to hit pause
for that because Rachel's having to improvise. Okay what was happening there?
I couldn't fill my jug. Why? Because it's too shallow. Okay so
it's too shallow. Essentially so each time that even though you know you were
coming over there you predicted you would be able to completely empty this
completely fill this. But when you got there you realise of course that each
time you weren't making the full use of your jug. So what would eventually happen
over a longer period of time? There's some sort of residual thing that she
can't get or it's not enough to do what she needs to do it with.
Let's try talking terms of rate. What's going to happen to the speed at
which Rachel can move the fluid over there? It's going to decrease. Meanwhile the
rate that you can new stuff over here is increasing. I've got more available.
I don't know, it's a constant. A weakness of this model
perhaps in real life we actually increase the
forwards and decrease the back until we reach a new position of equilibrium
where the rates of both become back to being the same.