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Lecture Comments (2)

1 answer

Last reply by: Bryan Cardella
Thu Mar 26, 2015 4:02 PM

Post by Michelle Grussenmeyer on March 25, 2015

This Lab was awesome, and it really gave me a complete understanding of how osmosis works! Thanks!

Laboratory Investigation II: Egg Lab

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Egg Lab Introduction 0:06
    • Purpose
    • Materials
    • Time
  • Day 1 1:28
  • Day 2 3:59
  • Day 3 6:05
  • Analysis 7:50
  • Osmosis Connection 10:24
    • Hypertonic
    • Hypotonic

Transcription: Laboratory Investigation II: Egg Lab

Hi, welcome back to www.educator.com, this is laboratory investigation 2, the egg lab.0000

A little introduction for this egg lab, the purpose is to demonstrate the effects of osmosis on a chicken egg.0007

Osmosis is the movement of water to where there is less water by concentration.0016

When you get that hard shell off of the egg, you can do some amazing things with different levels of sugar concentration,0022

complete lack of sugar and a sugary kind of substance, in terms of making water go in and out of the egg.0030

Here is how it works, you need at least one chicken egg, plastic cup, an electronic scale, 2.1 g.0036

You do not even need to 0.01. If you have that great, some kind of electronic scale.0048

White vinegar also known as acetic acid, karo syrup, you can also use maple syrup,0054

any really thick highly concentrated sugar syrup will do, and distilled water.0060

The only thing you would really need to do this at home is some kind of bin,0067

some kind of container that you would put the vinegar in and have the eggs sitting there overnight.0073

The purpose of that is actually to dissolve the shell.0081

I will mention more about that in a second.0083

The time required is really 3 days to do this.0086

Day 1, going into day 1 you have to have that egg soaking overnight in white vinegar, like I said earlier that is acetic acid.0090

As it is sitting there, you will see little bubbles, you will see like something going on.0099

It is because gradually that acidic liquid, it is dissolving the hard shell.0104

Just underneath that shell is a membrane.0111

The egg will still be intact, it will be more fragile, you do not want to poke it too hard.0114

You will dissolve that hard shell and that is how you make this lab possible.0119

Getting rid of that shell, you can have that water moving back and forth happen very efficiently.0125

When you see the eggs sitting in there the next morning, if you have done this overnight, 0131

it might look like it is foamy, and that is really like dissolved shell material, you can actually rub it off.0135

I would do with a gloved hand, personally, but you can rub it off.0143

As long as you rub gently, you would not pop the egg.0147

First off, you got to take the mass of the cup you would be using.0150

The reason why is because when you put the cup on the scale with the egg in it, you want to be able to subtract the mass of the cups.0153

You know just the mass of the egg that is inside of it.0164

Make sure you know the mass of just the cup going into it.0167

You know is the cup 5g, whatever it is.0172

Remove the egg from the vinegar, put it in a cup then measure them together.0177

Subtract the cup mass then you get a mass of the egg.0182

Let us say the mass of the egg initially is 82 g.0186

I have done this many times before, that is a typical mass.0192

It could be 90 but let us say the egg starts out as 82 g, we know the starting out mass of a normal egg without its shell.0195

We got to pour karo syrup into the cup surrounding the egg until it is completely covered by that karo syrup.0205

There is an old tiny photo of someone holding a giant bin of karo syrup.0214

You could make 20 pecan pies out of that.0220

But then, you are done, that is it for day 1.0224

You set the cup aside, maybe put some Ceram wrap or plastic wrap on the outside of it, so you do not have getting to karo syrup, or ants.0227

You wait overnight.0236

Day 2, record your observations of the egg.0240

If you look in that little cup with the karo syrup surrounding the egg, you will never see the difference.0243

How is it different from the previous day?0249

What you are going to see is, it is going to look wrinkled, it is going to look shriveled.0251

You can assume that, if it look shriveled, maybe it lost some water.0257

We will measure and see if maybe it did lose some water mass.0262

Dispose the karo syrup carefully. What I would do is, if you have a plastic cup, you squeeze the cup but do not squeeze the part of the egg.0266

Gently pour out the karo syrup and the egg is trapped and it would not come out.0273

Once you get a lot of that karo syrup out, measure the cup with the egg in it, subtract the cup weight again.0279

The question is, how is the mass changed?0286

Let us say it dropped down to 68 g, that has lost a lot of weight.0291

It was 82, it lost 14 g of water.0299

Why do you think the change occurred?0303

A good hypothesis could be water left the egg and went into the karo syrup.0306

Because, the karo syrup is more highly concentrated with that sugar, it had sucked the water out.0312

Since water goes to where there is less water by concentration, that could have definitely happened.0320

We did not put distilled water in the cup until the egg is fully submerged.0325

You are ready, you are done for the day.0335

This is an older electronic scale compared to some of the more modern looking ones, 0337

but this is good enough, this actually goes to 0.01 g.0343

Once you have distilled water, you could use tap water but distilled water means that 0350

they took all that other stuff out of the water, it is just water.0355

Once it is fully submerged, you let it sit until day 3.0361

Day 3, record the observations of the egg.0367

What does it look like now?0370

How is it different from the previous day, it is going to look pretty solid, in terms of how puffy it is.0372

Dispose the water carefully like before with disposing the karo syrup.0384

Measure the egg without the water, once again how is the mass changed?0389

I started out at 82, down to 68, let us say now it is 97 g, more massive than it was to begin with.0393

That is why it looks like it is kind of puffy.0406

Why did the change occur?0410

The opposite is true now, if you get a scenario where, the egg in day 2 was in pure water, water goes to where there is less water.0413

Water kind of crossed the membrane from outside the egg inside the egg, 0422

to where there is a lot of other molecules in that aqueous egg environment.0427

The egg is now much more bouncy.0432

In my class, we do this thing where we take the bouncy eggs, pull out paper towels on the lab tables, 0434

we are to contest to see whose egg can survive dropping the highest distance.0441

The average egg, you drop it 6 inches or 8 inches, several centimeters, and it will actually bounce and not break.0446

It is amazing that it is a raw egg without its shell.0455

Some of them they pop after dropping it just that much.0459

Actually, I had an egg once that dropped 20 inches and it did not break, amazingly.0464

Some analysis, what happened here?0473

The egg has less mass after being in a sugary syrup.0477

After being in that sugary syrup, it got sucked, it got a lot of water sucked out of it because higher sugar concentration outside of the egg.0483

The egg had more mass after being in the water because the opposite was true.0495

We added in pure water, the pure water, you kick it in more highly concentrated than that, 0500

water goes from a higher concentration of water to a lower concentration.0505

The water went into the egg across the egg membrane.0509

The sugar molecules is way too large to cross the membrane of the egg.0513

Think about it this way, if that is the egg and I’m going to zoom in like exaggerating this.0517

We are zooming into there.0529

Here is the membrane, we are zooming into there, that little line, this is the membrane, these are porous membrane.0538

Here is inside the egg, here is outside the egg.0550

When we put in karo syrup, they are these giant sugar molecules compared to the membrane pores.0554

You can see that these sugar molecules, these red dots, are too big to fit through there.0564

This is in a diffusion lab, we do not have a sugar crossing the membrane.0571

But, the little water molecules, these blue dots, they can definitely pass through.0575

When the egg is in the karo syrup, these blue dots, a lot of them move out.0583

Water wants to equalize the concentration of sugar on both sides.0591

It is going to go to the more sugary part, water gets sucked out of the egg.0595

The opposite happens when it is in pure water in day 2.0600

Here is a U-tube showing how this works, semi permeable membrane that is only letting the water cross.0605

You can see that the dissolved salt, in this case it is not sugar in this example, it is a dissolved salt.0612

It is not crossing but the water is, and this is osmosis.0617

That is how this lab works.0623

The connection osmosis, I already talked about this a bit but a little bit more is a concluding statement.0627

Water moves to where there is less water by concentration, that is the definition.0632

The karo syrup has less percentage of water than the inside of the egg.0636

We initially put in a hypertonic environment, more highly concentrated with sugar than the inside.0640

The distilled water had much more percentage of water than the inside of the egg.0650

Because it is 100% water, that is hypotonic.0654

When you have an egg or a cell in a hypertonic environment and it is only permeable to water, water is going to go into hypertonic side.0658

Conversely, when you have a cell or an egg in a hypotonic environment, the opposite will happen.0668

Water will go inside the egg and it got really puffy because of that, that is fun.0673

There is that egg, it is quite an amazing structure.0680

Thank you for watching www.educator.com.0685