Supersaturated Solution

Hi, my name is Ronn Fieldhouse.

I'm the Chemistry Curriculum Specialist here at PASCO scientific.

Today I'd like to show you a supersaturated solution.

Often, students have a hard time conceiving what this is.

The definition is that it's more than the maximum amount of solute

that can be dissolved under the set conditions.

What I did to create this solution is I dissolved

50 g of sodium acetate trihydrate in just 5 mL of water.

That's a lot of solute and very, very, very little solvent.

Supersaturated solutions are always temporary solutions.

Even though this one looks very stable right now,

all I need to do is add one crystal,

one little bump, and it starts the process.

I'm going to start my data collection.

You can see it's reading about 35.4 degrees.

It's kind of warm in this room.

I did let it cool down to room temperature.

All I need to do is add one example of the lattice,

one example of that plus/minus, plus/minus pattern,

to start the rest of this meeting that same pattern.

So just a few sprinkles.

There, you can see the crystals forming.

It takes a moment to start seeing a temperature change,

but any second now, it's going to start increasing.

After I dissolved it, what I did is I heated it up

on a hot plate very gently and then let it cool.

Don't let it boil -- that starts to degrade the acetate.

You can see I'm already up to about 39.5 degrees.

Let it sit very carefully, nobody bump it, nobody touch it,

let it cool down to room temperature, then very gently bring it over.

Now, I've set it on top of a temperature probe.

That's one of our Fast Responses. I didn't tape it. I just simply set it on there.

You can see I'm starting to get very good temperature readings.

Whatever energy I put in to dissolve this solution,

I am now getting back.

Not only is it an example of the supersaturated solution,

it's also a good example of the conservation of energy.

I see it's starting to plateau.

It looks like I got about 10 degrees temperature change.

That's my supersaturated demo.

Thank you very much for listening.