Hi. It's Mr. Andersen and today I'm going to walk you through the osmosis lab. Sometimes
people call this the potato lab. And so what you need is a potato. You need a potato coring
device so we can get a similar amount of potato in each one. I use a razor blade to do much
of the trimming. I also need six different test tubes. These six different test tubes,
you can see that I've already labelled them. They've got my name on it and then they have
the different concentrations of sucrose. And so we're going to start with 0.0 molar sucrose
which is essentially distilled water. We're going to go 0.2, 0.4, 0.6, 0.8, and finally
we're going to work our way up to 1.0 molar sucrose solution. So the lab is pretty straight
forward. We're going to put potato cores in each of these. We're going to get their mass
today. And they we're going to let it sit overnight. And then we're going to get their
mass again tomorrow. And we're going to see what happens, what changes we see in the mass
of the potatoes over time. So this is what you'll use. Make sure you put your name on
it. Also you need a sheet of paper. That's going to have your initial masses today. And
then you'll need to share, I've made a bunch of sucrose solution for the class. And so
you're going to share that. It's really hard to pour out of these Erlenmeyer flasks. And
so what I'll do is I'll put a little beaker in front of each one. So essentially you go
from the Erlenmeyer flask to the beaker. And then from the beaker into each of your test
tubes. So let me show you how to, I'll just set up one. I won't show you all of them.
But I'll show you how you would set up just one test tube. So what you're going to use
is a potato. And we'll use a potato corer. So what you do is you push like this through
it. And then you're going to go all the way out the other side. Don't ram it into your
hand because you could cut your hand with it. And then essentially you push it like
this. And the potato corer comes out. So I'm going to do another one of those. You'll probably
have to use a couple of potatoes to get all of your cores. So we go like that. Pop that
out. Alright. So in each of the different test tubes we're going to put 2 potato cores.
And so the best way to do this, let me see if I turn it this way, is to since we have
6 different test tubes, you're going to put 2 in each, what I would do is I would punch
them all out. Get them roughly the same size. And then you can trim them. Because we want
them, we want to get rid of the skin. And so you can imagine if I had 12 of them we
would trim them off. And so they're all going to be roughly the same length. We're looking
at the percent change in mass and so if they're not exactly the same that's okay. So you cut
them all off. And so these would be my potatoes or my potato cores for the 0.0 ml or zero
molar water. I'll then take a scale. So let me zero that. So we'll zero that. And then
I put my 2 potato cores that are going to go in the 0.0 molar solution right here. And
so I write down their mass. So today they are 8.79 grams. I'm going to, before I forget,
put those immediately into my 0.0 molar test tube like that. And now I'm going to add some
of that distilled water. So there's some parafilm on the top. Make sure that goes back when
you're done. Because we'd hate to have us lose water. So evaporation could screw us
up. And then you're going to use the corresponding beaker. And then we're going to fill it up.
So I'm going to fill it up like this. You want to make sure as we fill these up that
you cover the potatoes. And that it's the same in each of these test tubes. We're going
to have about the same volume in each of them. To cover it up, because if we don't cover
it up tonight there's going to be a lot of evaporation of the water. And so we're going
to use parafilm to do that. Parafilm is like a wax. You always cut way more, way LESS then
you think you're going to need because you stretch it over. So you essentially hold it
on one side like that. You wrap it over the top. And then you can kind of heat it up with
your hand. And then it will keep the water inside there. So this our 0.0 molar potato
cores. So we're going to put them like this. We'll go through all the other ones. Remember
you're going to put a different sucrose solution in each of those. And then after we've got
their mass today we're just going to wait 24 hours. And after 24 hours we're going to
dump out the water and remass each of those potato cores. This lab is super easy. You'll
always get perfect data as long as you don't mix up which of the potato cores is which.
And so what are we looking at? Well what we're going to do is we're going to take their mass
today. We'll take their mass tomorrow. And then we're going to see their percent mass
change. In other words how much they change. You're going to have some that get a positive
percent change in mass. And some that get a negative. And so I'll show you a little
formula for how you do that. But I think that's pretty much it. So I hope that's helpful.