diffusion and osmosis egg experiment

Use a giant cell—a de-shelled chicken egg—to explore the comings and goings of cellular substances.

• Several chicken eggs
• Large container, such as a wash basin or large bowl
• Pencil and notepaper (or similar) for recording information
• Several substances in which to soak or bury the de-shelled eggs, such as distilled water, dry salt or saltwater solutions, colored water, corn syrup, rubbing alcohol, cornstarch, or baking soda
• Containers to hold the soaking eggs
• Plastic wrap (not shown)
• Masking tape and marker for labeling containers
• Optional: nitrile or latex gloves for handling eggs, glass jars or other small objects to hold down floating eggs

• Determine the treatments you’ll be using on your eggs, and prepare the substances you’ll need. You can make salt-water solutions by dissolving different amounts of table salt in containers of water (e.g. 100g, 200g, 300g of salt (NaCl) per liter). You can make solutions of food coloring by adding a few drops of each color into containers of water. Remember to label your containers as you work.

Use a scale to find the mass of each de-shelled egg before treatment. Record the result on notepaper.

Place one egg in a labeled container and cover it with your chosen treatment. (If the egg floats, you may use something to hold it down, such as a glass jar; see photo below.) Repeat for each of the remaining treatments. Be sure to set aside an untreated "control" egg. After taking its mass, cover the control egg with plastic wrap, and set it in a container alongside the treatment eggs.

Place the treatment containers somewhere they can sit for at least a day at room temperature. Observe any changes that occur in the eggs during the first hour or so of soaking and record your observations.

Observe any changes in the color, size, or shape of your experimental eggs. Record your observations. Then, gently remove your sample eggs from their treatments to measure and record the mass of each one (see photo below). Remove the plastic wrap from the control egg and measure its mass too. Calculate the percentage change in mass for each egg by dividing the final mass by the starting mass and multiplying by one hundred percent.

In a separate bowl, carefully dissect the egg by piercing the membrane. Record your observations.

How did each egg change? Did its mass increase or decrease? Do you see anything in common with the treatments that enlarged the eggs? Which treatments made the eggs shrink, and which did not?

In general, the most dramatic changes to the mass, color, and shape of the eggs will occur within the first 24 hours of the experiment. Eggs submerged in corn syrup will have lost considerable mass and have the appearance of flabby sacks. Eggs soaked in distilled water will gain mass and appear dramatically swollen. Eggs in dilute salt solutions will gain mass, and even those in very concentrated solutions might gain mass. Eggs buried in salt or other dry media should lose mass.

The de-shelled eggs serve as good models of human cells. After the eggshell is removed, a thin membrane (actually, two membranes held tightly together) remains. This membrane, like those in human cells, is selectively permeable, allowing certain substances to pass through while blocking others.

Substances that can pass easily through the membrane of the egg will follow the principles of diffusion. They will move through the membrane from the side where they are at a higher concentration to the side where they are at a lower concentration (click to enlarge the diagram below). This movement will continue until the concentration on both sides is the same. While random molecular motion will cause individual molecules to continue moving back and forth across the membrane, the overall concentration on each side will remain in equilibrium, with equal concentrations on both sides.

The egg’s membrane is permeable to water. Movement of a solvent (such as water) across a semipermeable membrane from a less concentrated solution to a more concentrated one is called osmosis . When an egg is soaked in a solution that has a higher solute concentration (the relative amount of dissolved stuff) than the solute concentration inside the egg, water moves out of the egg and into the solution (see diagram below).

As a result, the egg loses mass and ends up looking deflated. An egg naturally has a lot of stuff inside, so the outside solution has to be very concentrated for this to happen. That’s the case when an egg is treated with corn syrup or buried in salt. By contrast, when an egg is treated with distilled water, or a dilute salt solution, the solute concentration is higher inside the egg than out, so the water moves into the egg, increasing its mass. It may be easier to think about osmosis in terms of water concentration rather than solute concentration. If the solute concentration is high, then the water concentration will be low by comparison.

Rubbing, or isopropyl, alcohol is at least 70% alcohol and therefore less than 30% water. This should cause water to move from the egg into the solution, and the egg should lose mass. In addition, the egg may appear white and rubbery. Alcohol that diffuses into the egg can denature the proteins, unraveling their three-dimensional structure and causing them to coagulate or join together. Egg proteins turn from translucent to white when they are denatured. In cooking, temperature is used to denature these proteins, but you may have noticed that alcohol has also "cooked" the egg and caused it to look hard-boiled.

The plasma membranes of your cells behave much like those of the egg. All of the trillions of cells in your body are like busy seaports with materials coming in and going out. Water, oxygen, and nutrients must pass through the plasma membrane into your cells, and wastes must leave. When the concentration of oxygen is higher in your lungs than it is in your blood, for example, the oxygen diffuses into red blood cells through capillary walls. Your flowing blood then transports that oxygen to your tissues. From there, the oxygen diffuses into other cells to be used in cellular respiration. Through a similar process, water in the stomach moves into the bloodstream and is then carried to the cells, where it supports a variety of essential bodily functions.

Predict what would happen if you placed the shrunken eggs in plain water overnight. Do the experiment and explain your results.

In this activity, not only can you measure how much material moved into or out of a treated egg, but you can also chemically determine whether molecules moved across the membrane. If you break the egg into a dish, or save some of the soaking solution, you can use chemical tests to see what’s there. For example, you can use Benedict’s solution to test for simple sugars, iodine to test for starch, or Biuret solution to determine whether or not protein exited the egg as it soaked.

When using this activity with large groups of students or multiple classes, have each group apply only one treatment, and then analyze the data collected from all groups. Having each small group design an experiment with one egg will allow you to do the activity with fewer eggs per class, and collecting several sets of data will enable students to identify any outliers.

This Snack is an excellent activity for introducing diffusion, osmosis, and the semipermeability of membranes and allows learners to engage in the NGSS Science and Engineering Practices. By collecting data from multiple classes, you can facilitate a discussion about what and how much data is necessary to count as evidence. Students can also use the evidence about what and how much material moves into and out of the egg to formulate a revisable model about how osmosis occurs and what might prevent or allow molecules to move through membranes. By incorporating related activities, such as the Cellular Soap Opera Snack, students can form a more complete conceptual model of the cell membrane and how molecules move along concentration gradients.

Note that it’s also important to discuss the idea that models such as this one have limitations. There are structural differences between the membranes of chicken eggs and human cells that result in differences in permeability. Some of the molecules that pass through the egg’s membrane in this activity would not pass through a human cell membrane because of their size (such as cornstarch) or their charge (such as Na + and Cl - from the salt). 

Related Snacks

• Plant Biology
• Human Biology
• Biology Cells Osmosis Experiment

Osmosis Experiment: Dissolving Egg Shells With Vinegar

How does osmosis keep you healthy.

Right now, as you read this, there are millions of things happening throughout your body. The food you ate just a bit ago is making its way through a watery slurry inside your stomach and small intestines. Your kidneys are working hard to excrete waste and extra water. The lacrimal glands near your eyes are secreting tears, which allow your eyelids to close without damaging your eyeballs. What’s one thing that all of these processes have in common? They all rely on osmosis: the diffusion of water from one place to another.

Osmosis factors heavily in each of these processes and is an important force for keeping every single cell in your body healthy. Osmosis is hard to see without a microscope. But if we create our very own model of a cell, using a shell-less chicken egg, we can see what happens when we manipulate the osmotic balance in the “cell”!

• 3 glasses (large enough to fit the egg plus liquid)
• 3 butter knives
• White vinegar (about 3 cups)
• Distilled water (about 2 cups)
• Light corn syrup (about 1 ¼ cups)
• Slotted spoon
• Measuring cup (1 cup)
• Measuring spoons (1 tablespoon and ½ tablespoon)
• Sticky notes and marker
• Scale (optional)

Note : It’s okay to touch the eggs, but remember to wash your hands afterwards to avoid any nasty surprises!

1. Place one egg in each glass. Pour in enough vinegar to cover each egg. Bubbles will start to form around the egg, and it’ll float up. To keep it submerged, put a butter knife in the glass to hold it down.

2. Put the three glasses in the refrigerator and allow to sit for 24 hours.

3. Gently holding the egg in the glass, pour out the old vinegar. Replace with fresh vinegar, and let sit in the refrigerator for another 24 hours. Repeat this process until the shells are fully dissolved and only the membrane remains. This should take about 2-3 days.

4. Gently remove the eggs using the slotted spoon and rinse with tap water in the sink. Rinse out the empty glasses as well.

5. Gently put the shell-less eggs aside for a moment on a plate.

6. Prepare three different sugar-water solutions as follows, labeling with sticky notes:

Glass 1: Label “hypertonic”. Pour in one cup of corn syrup.

Glass 2: Label “isotonic”. Add 1 ½ tablespoons corn syrup to the one cup measuring cup, and fill the remainder with distilled water. Pour into glass (make sure you get all the corn syrup out!) and stir to dissolve.

Glass 3: Label “hypotonic”. Pour in one cup of distilled water. Gently put one shell-less egg in each of the glasses, and let sit in the refrigerator for another 24 hours.

7. Remove the glasses from the refrigerator, and gently put the eggs on a plate. If you weighed the eggs before putting them in each solution, weigh them again. What happened to each of the eggs?

How does osmosis work?

Osmosis is the scientific term that describes how water flows to different places depending on certain conditions. In this case, water moves around to different areas based on a concentration gradient , i.e. solutions which have different concentrations of dissolved particles ( solutes ) in them. Water always flows to the area with the most dissolved solutes, so that in the end both solutions have an equal concentration of solutes. Think about if you added a drop of food dye to a cup of water – even if you didn’t stir it, it would eventually dissolve on its own into the water.

In biological systems, the different solutions are usually separated by a semipermeable membrane , like cell membranes or kidney tubules . These act sort of like a net that keeps solutes trapped, but they still allow water to pass through freely. In this way, cells can keep all of their “guts” contained but still exchange water.

Now, think about the inside of an egg. There’s a lot of water inside of the egg, but a lot of other things (i.e. solutes) too, like protein and fat. When you placed the egg in the three solutions, how do you think the concentration of solutes differed between the inside of the egg and outside of the egg? The egg membrane acts as a semipermeable membrane and keeps all of the dissolved solutes separated but allows the water to pass through.

How did osmosis make the eggs change size (or not)?

If the steps above work out properly, the results should be as follows.

In the case of the hypertonic solution, there were more solutes in the corn syrup than there were in the egg. So, water flowed out of the egg and into the corn syrup, and as a result the egg shriveled up.

In the case of the isotonic solution, there was roughly an equal amount of solutes in the corn syrup/water solution than there was in the egg, so there was no net movement in or out of the egg. It stayed the same size.

In the case of the hypotonic solution, there were more solutes in the egg than in the pure water. So, water flowed into the egg, and as a result, it grew in size.

Osmosis and You

Every cell in your body needs the right amount of water inside of it to keep its shape, produce energy, get rid of wastes, and other functions that keep you healthy.

This is why medicines that are injected into patients need to be carefully designed so that the solution has the same concentration of solutes as their cells (i.e. isotonic). If you were sick and became dehydrated, for example, you would get a 0.90% saline IV drip. If it were too far off from this mark it wouldn’t be isotonic anymore, and your blood cells might shrivel up or even explode , depending on the concentration of dissolved solutes in the water.

Osmosis works just the same way in your cells as it does in our egg “cell” model. Thankfully, though, the semipermeable membrane of the egg is much stronger, so you don’t have to worry about the egg exploding as well!

Related Topics

Choose one of the following categories to see related pages:.

• Experiments

Share this Page

Lindsay graduated with a master’s degree in wildlife biology and conservation from the University of Alaska Fairbanks. She also spent her time in Alaska racing sled dogs, and studying caribou and how well they are able to digest nutrients from their foods. Now, she enjoys sampling fine craft beers in Fort Collins, Colorado, knitting, and helping to inspire people to learn more about wildlife, nature, and science in general.

• Basic Types of Cells
• Cell Organelles
• Connective Tissue Cells
• Epithelial Cells
• Introduction to Cells
• Muscle Cells
• Nerve Cells
• Osmosis Experiment
• Structure of the Cell Nucleus
• Structures of the Cell Cytoplasm

Science Newsletter:

Full list of our videos.

Teaching Biology?

How to Make Science Films

Read our Wildlife Guide

New From Untamed Science

BIOLOGY JUNCTION

Test And Quizzes for Biology, Pre-AP, Or AP Biology For Teachers And Students

Osmosis & Diffusion in Egg Lab

Objective: In this investigation, you will use a fresh hen’s egg to determine what happens during osmosis & diffusion across membranes.

Materials: (per lab group) 1-2 fresh hen eggs in their shells, masking tape & marker, distilled water, clear sugar syrup (Karo, for example), vinegar, clear jar with lid, tongs, electronic balance, paper towels, paper, pencil

• Label the jar with your lab group & the word “vinegar”.
• Mass the egg with the electronic balance & record in the data table.
• Carefully place the raw egg into the jar & cover the egg with vinegar.
• Loosely re-cap the jar & allow the jar to sit for 24 to 48 hours until the outer calcium shell is removed.
• Open the jar & pour off the vinegar.
• Use tongs to carefully remove the egg to a paper towel & pat it dry.
• Record the size & appearance of your egg in your data table.
• Mass the egg on an electronic balance & record.
• Clean and re-label the jar with your lab group & the word “distilled water”.
• Carefully place the egg into the jar & cover the egg with distilled water.
• Loosely re-cap the jar & allow it to sit for 24 hours.
• Open the jar & discard the distilled water.
• Clean and re-label the jar with your lab group & the word “syrup”.
• Carefully place the egg into the jar & cover the egg with clear syrup.
• Open the jar & pour off the syrup.
• Use tongs to very carefully remove the egg & rinse off the excess syrup under slow running water.
• Pat the egg dry on a paper towel.
• Clean up your work area & put away all lab equipment.

Questions & Conclusion:

1. Vinegar is made of acetic acid & water. Explain how it was able to remove the calcium shell.

2. (a) What happened to the size of the egg after remaining in vinegar?

(b) Was there more or less liquid left in the jar?

   (c) Did water move into or out of the egg? Why?

3. (a) What happened to the size of the egg after remaining in distilled water?

4. (a) What happened to the size of the egg after remaining in syrup?

5. Was the egg larger after remaining in water or vinegar? Why?

6. Why are fresh vegetables sprinkled with water at markets?

7. Roads are sometimes salted to melt ice. What does this salting do to the plants along roadsides & why?

Naked Eggs: Osmosis

Activity length, 10 mins. plus 24 hours, activity type, discrepant event (investigatable).

Diffusion is the spontaneous movement of any substance spreading from a higher concentration to a lower concentration, attempting to reach equilibrium.

Osmosis is similar, but is particular to solutions (dissolved mixtures) separated by a membrane.  Osmosis is the process in which water moves through a membrane. The natural movement of water is from the side of the membrane with a high concentration of water to the side with a low concentration of water.

After dissolving the eggshell, we are left with a membrane that holds the insides of the egg. This membrane is selectively permeable . This means that it lets some molecules move through it and blocks out other molecules. Water moves through the membrane easily. Bigger molecules, like the sugar molecules in the corn syrup, do not pass through the membrane.

You may have noticed that the egg expanded in the initial vinegar solution when you dissolved the shell. This is because the vinegar has a higher concentration of water than the inside of the egg.

To reach equilibrium , water molecules move from the vinegar into the egg through the semi-permeable membrane. If the membrane were completely permeable, water molecules would move in and protein would move out until both solutions were the same concentration. Since the egg membrane is semi-permeable, water can move in but proteins cannot move out.

If a naked egg is placed in the corn syrup the egg will shrink . This is also due to osmosis, but in the opposite direction. The corn syrup is mostly sugar. It has a lower concentration of water (25% water) than the egg (90% water). To reach equilibrium, osmosis causes the water molecules to move out of the egg and into the corn syrup until both solutions have the same concentration of water. The outward movement of water causes the egg to shrivel.

Describe osmosis.

Determine the direction of water movement based on solution concentrations.

Describe the function of a semi-permeable membrane.

Per Class: corn syrup or simple sugar solution (enough to cover each group’s egg_ scale (optional)

Per Group of 3–4 students: “naked” (shell-less) egg from Naked Eggs: Acid-Base Reaction activity jar or bowl slightly larger than the egg big spoon water

Key Questions

• Why is your naked egg that was soaked in vinegar bigger than a shelled egg?
• Why does the egg in corn syrup change shape and weight?
• Does the egg soaked in water change shape and weight?
• What could you do to return the egg to its original form?

Prior Experiment – make a  Naked Egg

Preparation

• Designate a “corn syrup pouring station” at your desk so that you can monitor the amount of corn syrup students are using (to avoid wasting).
• Place a naked egg in a jar of plain water to use as a “control”. Treat it the same way as the corn syrup-covered egg.
• Weigh your egg and note the measurement.
• Put your naked egg in a jar and add enough corn syrup to cover the egg.
• Store the egg in a refrigerator (or somewhere cool) for 24 hours.
• After 24 hours, scoop out the egg and observe the changes.
• Weigh the egg again and note the measurement.
• Draw a diagram of your egg in the corn syrup. In what direction is osmosis occurring (the movement of water molecules across the membrane)?
• Return the corn syrup-covered shriveled egg to its non-flabby former shape! Carefully lift the flabby egg from the corn syrup and place it in a container of water. Leave the egg in the water for 24 hours. Osmosis will occur; that is, the water will migrate from the side of the membrane where water molecules are abundant (i.e. outside the egg) to the side where water molecules are less abundant (inside the egg). After 24 hours, the egg will be plump again!
• Experiment with naked eggs by soaking them in other solutions. What happens if you put the egg in water with food colouring? Or salty water?

About the sticker

Artist: Jeff Kulak

Jeff is a senior graphic designer at Science World. His illustration work has been published in the Walrus, The National Post, Reader’s Digest and Chickadee Magazine. He loves to make music, ride bikes, and spend time in the forest.

Comet Crisp

T-Rex and Baby

Artist: Michelle Yong

Michelle is a designer with a focus on creating joyful digital experiences! She enjoys exploring the potential forms that an idea can express itself in and helping then take shape.

Buddy the T-Rex

Science Buddies

Artist: Ty Dale

From Canada, Ty was born in Vancouver, British Columbia in 1993. From his chaotic workspace he draws in several different illustrative styles with thick outlines, bold colours and quirky-child like drawings. Ty distils the world around him into its basic geometry, prompting us to look at the mundane in a different way.

Western Dinosaur

Time-Travel T-Rex

Related Resources

Naked eggs: acid-base reaction, in this activity, students describe the effects of an acid on an eggshell. the reaction of the eggshell in vinegar…, eggstraordinary eggsperiments, there are many easy and fun experiments that can be done with eggs, encompassing a number of different scientific principles., rubber bones, in this activity, students see that without calcium, bones become floppy. although bones in museums are dry, hard, brittle or…, related school offerings.

Reactions and Indicators (Grades 6-7)

Visit Search: Sara Stern Gallery

Visit Ken Spencer Science Park

We believe that now, more than ever, the world needs people who care about science. help us fund the future and next generation of problem solvers, wonder seekers, world changers and nerds..

• EXPLORE Random Article
• Happiness Hub

How to Understand Osmosis with Eggs

Last Updated: August 10, 2021 References

This article was co-authored by Meredith Juncker, PhD . Meredith Juncker is a PhD candidate in Biochemistry and Molecular Biology at Louisiana State University Health Sciences Center. Her studies are focused on proteins and neurodegenerative diseases. There are 10 references cited in this article, which can be found at the bottom of the page. This article has been viewed 29,059 times.

Osmosis is a biological and chemical process that describes the movement of water from a less concentrated solution to a more concentrated solution. During osmosis, water molecules move through a semipermeable membrane to create an equal distribution of water on both sides. The growing and shrinking egg test uses eggs, distilled vinegar, corn syrup, and water to demonstrate this important and complicated natural process. This fun experiment helps showcase osmosis in a fun, exciting, and visual way! [1] X Research source

Dissolving the Eggs’ Shells

• This number will be important as you compare other data that you will collect throughout the project.

• Keep the eggs out of direct sunlight and be sure that the temperature is stable.
• Carbon dioxide bubbles will cover the eggs as the vinegar dissolves the shells. [4] X Research source Beneath an egg’s shell lies the egg membrane, which is a layer that is made up of proteins that help protect the egg’s center from bacteria. [5] X Research source

• If you use a spoon to remove the eggs, you may risk breaking or damaging the eggs. [6] X Research source

Growing One of the Naked Eggs

Shrinking One of the Naked Eggs

• Corn syrup has a high density due to its high concentration of sugar molecules, and it is denser than both water and vinegar. This disparity in density will demonstrate how osmosis can have a different effect on the appearance of the egg.

Following the Scientific Method

• Record the egg’s circumference. You may wish to observe how the circumference of the eggs changed throughout the experiment as well. Use a flexible tape measure to measure the widest part of the egg. Record this data and gently measure the egg in the same place after each section of the experiment. [10] X Research source
• Measure the amount of liquid used. Keep track of how much water, vinegar, and corn syrup you placed in each cup. When the egg has been removed, pour the remaining liquid into a beaker or a measuring cup. Record the amount of liquid lost or gained during the experiment.

• Was the temperature outside particularly hot that day? Did you accidentally spill some of the vinegar when retrieving your egg? Make note of anything that could have altered the data.

Community Q&A

• Take before and after photos during each section of the experiment. This will help you observe how osmosis can affect the size of the eggs in various environments. [12] X Research source Thanks Helpful 0 Not Helpful 0
• Place the naked eggs in salt water and sugar water and record how osmosis affects the eggs in those solutions. Thanks Helpful 0 Not Helpful 0
• Do not eat the egg. Remember that the egg is raw and has been sitting in a mixture for several days. [13] X Research source Thanks Helpful 1 Not Helpful 0

Things You'll Need

• White vinegar
• Notebook or computer
• Faucet and sink
• Flexible tape measure (optional)

You Might Also Like

• ↑ http://www.science-sparks.com/2011/08/29/shrinking-eggs/
• ↑ http://imaginationstationtoledo.org/educator/activities/how-to-make-a-naked-egg
• ↑ https://www.stevespanglerscience.com/lab/experiments/growing-and-shrinking-egg/
• ↑ https://www.exploratorium.edu/cooking/eggs/eggcomposition.html
• ↑ https://www.youtube.com/watch?v=SrON0nEEWmo
• ↑ http://www.aeb.org/images/PDFs/Educators/g6-9-shrinking-and-growing-eggs.pdf
• ↑ https://www.csub.edu/chemistry/_files/Egg%20OsmosisAO.pdf
• ↑ http://www.sciencekids.co.nz/projects/thescientificmethod.html

About this article

Reader Success Stories

Isabel Hurst

Apr 1, 2020

Did this article help you?

Sam Sislbee

Nov 7, 2019

• About wikiHow
• Terms of Use
• Privacy Policy
• Do Not Sell or Share My Info
• Not Selling Info

April 16, 2015

The Big Eggshell Breakdown

Put de-shelled eggs in different liquids and watch how they grow and shrink

By Exploratorium

Key Concepts Chemistry Cells Diffusion Osmosis   Introduction Have you ever thought of a chicken egg as one big cell? Of course it is made up of many, many actual cells. But you can use it as a model to explore how different fluids get transferred from across cell membranes—and to other cells. This process is happening right now on a much smaller scale in your own body! But to see it with the naked eye we can try this macro-activity!   Background Every cell of our bodies is enclosed in a plasma membrane, a complex boundary made of lots of different layers. This separates the cell contents from the surrounding world outside the cell, which is often composed of fluid. These membranes play a large role in maintaining a proper balance of contents inside the cell (homeostasis) by controlling what passes through them. One of the most important characteristics of plasma membranes is their selective permeability, which means that they allow some substances to pass freely yet restrict others. See how an egg can do this on a scale you can observe!   Materials

A few cups or jars—large enough to hold an egg and enough liquid to submerge it

White vinegar—enough to submerge an egg

Large serving spoon

Water—enough to submerge an egg

Corn syrup—enough to submerge an egg

  Preparation

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing . By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Place the egg in a cup or jar and then pour in enough white vinegar to completely cover it. Observe the egg. Do you see tiny bubbles forming on the shell?

Cover the egg and leave it for 24 hours.

  Procedure

The next morning ladle the egg out of the vinegar with the big spoon. Is the shell different? How so?

Dump the old vinegar and cover your now-squashy egg with fresh vinegar.

Let the egg sit another 24 hours.

Remove your egg and observe it again. Has it changed again?

On the third morning spoon out the egg and rinse it in the sink under the tap. Be careful: because the eggshell has been dissolving, the egg membrane may be the only thing holding it together. The membrane is not as durable as the shell. How does the egg’s exterior look now?

Put the naked egg in a cup of water and let it rest for eight hours. Does the de-shelled egg look the same? How has it changed?

Carefully remove the egg and put it in a cup of corn syrup for another eight hours. Has the appearance of the egg changed again? How?

[break] Observations and results When you first place the egg in vinegar, carbon dioxide is produced as the acidic vinegar reacts with the calcium of the shell. As the egg sits in the vinegar, the shell is slowly dissolving away, producing a "de-shelled" egg. The eggshell should be totally gone by the third day, with a blob of egg white and yolk remaining inside a thin membrane.   The de-shelled eggs are good models of human cells. After the eggshell is gone, a white membrane remains. (It's actually two membranes, but they're held tightly together.) This membrane, like those of human cells, is selectively permeable, and the entire egg can be a model for a single cell.   Substances that can pass easily through the egg’s membrane will follow the principle of diffusion: They will move from the side of the membrane where they are at higher concentration to the side where they are at lower concentration. This exchange will continue until the concentrations on both sides of the membrane are equal.   Water can pass freely through a cell's membrane. (The movement of water across a membrane is a special version of diffusion called osmosis . ) When an egg is soaked in a solution in which the concentration of water is higher than that inside the egg, water moves from the outside solution, across the membrane and into the egg. As a result, the egg plumps up and grows larger. This is what happened when the egg was in water.   When an egg is soaked in a solution where the concentration of water is lower than that inside the egg, however, water moves from the egg, across the membrane, and into the outside solution. As a result, the egg loses mass and may end up looking like a deflated balloon. This is what happened when the egg was in corn syrup.   The plasma membranes of our cells behave much like those of the eggs. Water, oxygen and nutrients must pass through the plasma membrane into our cells and waste must exit. Oxygen diffuses into red blood cells in our lungs and they transport it to our tissues, where the gas diffuses into other cells. Water in the stomach and intestines moves via osmosis into the bloodstream.   More to explore The Science of Eggs , from Exploratorium Take an Egg for a Spin , from Exploratorium Fast Pickling , from Oakland Discovery Center  

This activity brought to you in partnership with Exploratorium

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

4 Diffusion and Osmosis

Introduction.

The ability of cells to move molecules in/out of their plasma membrane is critical to their survival. This means that as a multicellular organism, your survival is also dependent upon this molecular movement. At the same time, it is equally vital to be able to prevent the passage of certain molecules into or out of the cells. Thus, the cell membrane serves as a gateway through which all substances must pass when traveling into or out of the cell. How does the cell control this movement? To understand this process, we must first discuss what causes molecules to move in the first place.

At any temperature above absolute zero (-273 °C; the temperature at which molecular movement ceases), all molecules are in motion. This is because all molecules contain energy, and this energy causes them to vibrate and jiggle about. Adding more energy causes the molecules to increase their motion. Think about an ice cube. At low temperature, the water molecules are frozen in a crystalline matrix. Even though they are in a solid state, the molecules are still vibrating within that matrix. If you add heat (a form of energy), what happens to the ice? As the molecules absorb the heat energy, they increase their movement and begin to bump and slide past each other. This is what happens when ice changes states from a solid to liquid water. What if we keep adding heat energy? The molecules move more and more, bumping and pushing each other until they force themselves to spread out and the water turns to a gaseous vapor.

Clearly, individual molecules are too small to see with the naked eye. However, as molecules move they bump into other material. We can actually observe this molecular movement in the form of Brownian motion. Brownian motion is the movement of small particles due to impacts from molecules moving around them.

A solution is a mixture of substances in which a minor component ( solute ) is dissolved in a major component (the solvent ). If you start with a pure solvent like water, and add some solute (e.g., a sugar cube), molecular movement causes the solvent molecules to bump into the solute molecules (think Brownian motion), causing the solute to spread out. This spreading of solute molecules is an example of a process called diffusion . Diffusion is the movement of any substance from an area of high concentration into an area of low concentration. Eventually, the solute will completely dissociate from its concentrated form and spread out evenly within the solvent. At this point the solute has reached equilibrium within the solvent.

Osmosis is a specific kind of diffusion in which water moves across a semipermeable membrane from an area of high water concentration to an area of low water concentration. A semipermeable membrane is a barrier that allows the passage of some substances but not others. In the case of osmosis, the semipermeable membrane allows water to pass through, but not solutes. For example, let’s say we have two solutions separated by a semipermeable membrane. Solution 1 on the left is composed of 90% water and 10% table salt. Solution 2  on the right contains 70% water and 30% table salt. If the membrane is permeable to water, but not to solutes, which way will the water diffuse?

Since diffusion involves movement of a substance from an area of high concentration to an area of low concentration, the water will diffuse “down” its concentration gradient , from Solution 1 into Solution 2. Which way will the salt move? Since the membrane is impermeable to solutes, the salt won’t move at all.

At the start of this process, Solution 1 has a higher concentration of water, and a lower concentration of salt than Solution 2. Thus, water diffuses out of Solution 1, into Solution 2. At the same time, water “wants” to move from Solution 2 into Solution 1, but due to the concentration gradient (of water), it cannot. We use the prefixes hyper (more), hypo (less), and iso (same) along with the root terms osmotic or tonic to describe the relationship between solutions separated by a semipermeable membrane. The amount of pressure needed to stop osmosis from taking place is called osmotic pressure . In the scenario above, it takes more pressure to stop water from diffusing into Solution 2 than into Solution 1. Thus, Solution 2 is hypertonic (hyperosmotic) relative to Solution 1. Solution 1 is hypotonic (hypoosmotic) relative to solution 2.

Over time, as Solution 1 loses water and Solution 2 gains water, the concentration gradient between the solutions will decrease. When both solutions reach the point where their water concentrations are equal, the solutions have reached equilibrium. At this point, both solutions are isotonic (isosmotic), and water passes freely between the solutions.

So, how does all of this diffusion and osmosis stuff pertain to living systems? Cell membranes are made up of a bilayer of phospholipid molecules . Phospholipids have a polar head (containing phosphates) and two non-polar tails (composed of fatty acids). The non-polar tails are hydrophobic (water hating), and because of this are driven away from the aqueous (water based) solutions inside and outside of the cell. The polar phosphate heads are hydrophilic (water loving), and they are attracted to water. This causes the phospholipid molecules to form into a complex with a non-polar internal layer encased between two polar layers. This bilayer forms the basic structure of all cellular membranes.

Gasses such as O 2 and CO 2 can diffuse directly across cell membranes. However, polar molecules like water and ions, or large nutrients and energy containing molecules, like glucose, cannot. Instead, these molecules must pass through channels in the membrane formed by proteins. Since protein channels only allow specific molecules to pass, the combination of phospholipids and transmembrane proteins makes the cell membrane semipermeable.

There are four ways that substances can be transported across the cell membrane.

• Simple diffusion through the phospholipid bilayer
• Facilitated diffusion through transport proteins
• Active transport through transport proteins
• Movement via vesicles (endocytosis and exocytosis)

Simple diffusion and facilitated diffusion take place passively as molecules move “down” their concentration gradients from areas of high concentration into areas of low concentration. By contrast, active transport uses energy to move molecules “up” their concentration gradient from areas of low concentration into areas of higher concentration. These processes are often during metabolism, including photosynthesis and cellular respiration.

For this week’s lab, we are going to focus on the process of osmosis and explore how concentration gradient affects this process. During this lab you will follow the scientific method to:

• Develop experimental hypotheses and predictions to explain the consequences of osmosis in animal cells
• Predict the direction water will move when given new biological scenarios
• Interpret data from a scientific article exploring the impacts of high solute concentrations on amphibians

Exercise 1. Osmosis in animal cells

Today you will use an egg membrane to model how osmosis works in animal cells. The egg you are observing was soaked in vinegar for ~48 hrs, which dissolved the egg shell. This “naked egg” now shows you the egg membrane, a layer of keratin proteins that separates the egg contents from its environment. The naked eggs were then subjected to two different treatments: exposure to corn syrup (25% sugar content) or exposure to distilled water. As you view the eggs, you’ll answer the following questions in your workbook:

• Why is the naked egg that was soaked in vinegar bigger than a shelled egg?
• What changes do you observe in the naked egg that was soaked in corn syrup?
• Draw a diagram of the egg in the corn syrup. Show the net direction of osmosis (the movement of water molecules across the membrane). Use your diagram to indicate why the egg in corn syrup changes shape and weight.
• What could you do to return the corn-syrup soaked egg to its original form?
• What changes do you observe in the naked egg that was soaked in distilled water? Does the egg soaked in water change shape and weight?

You’ll then complete practice problems to predict the direction of osmosis when given new scenarios.

Exercise 2. Osmosis in plant cells

Plants rely on water to maintain their structural rigidity. What happens to a plant when you don’t water it for several weeks? Clearly, it wilts. In plants, an organelle called the central vacuole functions to take up and hold excess water in the cell. The expansion of the central vacuole exerts pressure on the cytosol and presses the cell membrane against the cell wall. The force exerted by the water inside the cell against the cell wall is called turgor pressure . This force helps the plant remain upright. When the plant loses water, the central vacuole shrinks, turgor pressure is reduced, and the cell becomes flaccid. If the plant loses too much water, the plasma membrane may separate from the cell wall. This separation is called plasmolysis . We can cause plant cells to lose water by placing them in a hypertonic (hyperosmotic) environment.

If we immersed the plasmolyzed cells in a hypotonic environment, they would take up water and regain turgor pressure. However, the cells lose water faster than they can take it in, so this process takes longer than we have time available in lab.

• Obtain a fresh leaf from the supplied Elodea plant, a clean slide, and a coverslip.
• Place the Elodea leaf on the slide with a drop of pond water and cover with the coverslip.
• Observe the plant cells under normal (isosmotic) conditions, and draw them in Figure 4.4.
• Add 1 or 2 drops of 20% NaCl solution to the edge of the coverslip.
• Observe the cells under the hypertonic conditions, and redraw the cells after a few minutes. Note your conclusions in the figure caption below.

Exercise 3. Article analysis: The impact of osmosis on amphibians

As your final exercise today, you’ll analyze a scientific article . Scientific articles are how scientists share their results, design their experiments, and learn about new scientific discoveries.

IMPACTS OF ROAD DEICING SALT ON THE DEMOGRAPHY OF VERNAL POOL-BREEDING AMPHIBIANS Nancy E. Karraker , James P. Gibbs , James R. Vonesh

Before lab, you’ll prepare by just reading the abstract of the article . The abstract is posted on Canvas for you. During class, your group will analyze the results of this article and record your analysis in your lab workbook.

Biology I: Introduction to Cell and Molecular Biology Lab Guidebook Copyright © by Alex Urquhart is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

Share This Book

Sciencing_Icons_Science SCIENCE

Sciencing_icons_biology biology, sciencing_icons_cells cells, sciencing_icons_molecular molecular, sciencing_icons_microorganisms microorganisms, sciencing_icons_genetics genetics, sciencing_icons_human body human body, sciencing_icons_ecology ecology, sciencing_icons_chemistry chemistry, sciencing_icons_atomic & molecular structure atomic & molecular structure, sciencing_icons_bonds bonds, sciencing_icons_reactions reactions, sciencing_icons_stoichiometry stoichiometry, sciencing_icons_solutions solutions, sciencing_icons_acids & bases acids & bases, sciencing_icons_thermodynamics thermodynamics, sciencing_icons_organic chemistry organic chemistry, sciencing_icons_physics physics, sciencing_icons_fundamentals-physics fundamentals, sciencing_icons_electronics electronics, sciencing_icons_waves waves, sciencing_icons_energy energy, sciencing_icons_fluid fluid, sciencing_icons_astronomy astronomy, sciencing_icons_geology geology, sciencing_icons_fundamentals-geology fundamentals, sciencing_icons_minerals & rocks minerals & rocks, sciencing_icons_earth scructure earth structure, sciencing_icons_fossils fossils, sciencing_icons_natural disasters natural disasters, sciencing_icons_nature nature, sciencing_icons_ecosystems ecosystems, sciencing_icons_environment environment, sciencing_icons_insects insects, sciencing_icons_plants & mushrooms plants & mushrooms, sciencing_icons_animals animals, sciencing_icons_math math, sciencing_icons_arithmetic arithmetic, sciencing_icons_addition & subtraction addition & subtraction, sciencing_icons_multiplication & division multiplication & division, sciencing_icons_decimals decimals, sciencing_icons_fractions fractions, sciencing_icons_conversions conversions, sciencing_icons_algebra algebra, sciencing_icons_working with units working with units, sciencing_icons_equations & expressions equations & expressions, sciencing_icons_ratios & proportions ratios & proportions, sciencing_icons_inequalities inequalities, sciencing_icons_exponents & logarithms exponents & logarithms, sciencing_icons_factorization factorization, sciencing_icons_functions functions, sciencing_icons_linear equations linear equations, sciencing_icons_graphs graphs, sciencing_icons_quadratics quadratics, sciencing_icons_polynomials polynomials, sciencing_icons_geometry geometry, sciencing_icons_fundamentals-geometry fundamentals, sciencing_icons_cartesian cartesian, sciencing_icons_circles circles, sciencing_icons_solids solids, sciencing_icons_trigonometry trigonometry, sciencing_icons_probability-statistics probability & statistics, sciencing_icons_mean-median-mode mean/median/mode, sciencing_icons_independent-dependent variables independent/dependent variables, sciencing_icons_deviation deviation, sciencing_icons_correlation correlation, sciencing_icons_sampling sampling, sciencing_icons_distributions distributions, sciencing_icons_probability probability, sciencing_icons_calculus calculus, sciencing_icons_differentiation-integration differentiation/integration, sciencing_icons_application application, sciencing_icons_projects projects, sciencing_icons_news news.

• Share Tweet Email Print
• Home ⋅
• Science Fair Project Ideas for Kids, Middle & High School Students ⋅

Egg Osmosis Experiments With Distilled Water & Salt Water

Science Project Egg Experiments

Osmosis happens when a solvent, like distilled water, diffuses across a membrane into a solution that has a higher concentration of some solute, like salt water. Eggs are a model system for demonstrating osmosis because the thin membrane that lies underneath the shell is permeable to water, providing a system that changes volume as water passes in or out of the egg's interior.

Goal of the Experiment

Inside the egg membrane is a concentrated solution of proteins and water. When the egg is soaked in distilled water, osmosis causes water to diffuse into the egg to equalize the concentration of water on both sides of the membrane, and the egg increases in volume. If that same egg is then soaked in concentrated salt water, osmosis causes the water to diffuse back out of the egg, and the egg decreases in volume. The goal of the experiment is to demonstrate the process of osmosis by measuring the change in volume of the egg and then relate this to how water moves in and out of living cells.

Time Requirements

If only one experiment is performed on each individual egg, you will need to plan on three days for the experiment. Two days may be required to dissolve the egg shell with vinegar so that only the rubbery membrane remains. One day is required to complete each osmosis experiment on a single egg. Demonstrating osmosis in both directions, diffusion of water into the egg and then out of the egg, will require an additional 24 hours, for a total of four days.

Material Requirements

In addition to the eggs and vinegar to dissolve the shell, you will need plastic cups or glassware to store the eggs while soaking, salt to make a concentrated salt solution, and some way to measure the change in volume of the egg, such as rulers to measure the egg's dimensions, balances to measure the change in mass, or graduated glassware to measure displaced volume. Keep a stock of cleaning supplies nearby to deal with broken eggs.

Experimental Variations

Simple variations can be made to the experiment to make it more interesting. Food coloring can be added to the distilled water to demonstrate with color that water from the cup is moving inside the egg. After the egg swells in size, it can be popped and colored water will come out. Solutions other than salt water can also be used to cause water to diffuse out of the egg, such as oils or syrups that have little to no water content. These will cause a larger decrease in the egg's volume than salt water.

Related Articles

Science project on how to float an egg, experiment on putting an egg in vinegar, egg flotation science project procedures, why does an egg shrink in different solutions, chemistry projects for diffusion in liquids, science projects with vinegar & egg shells, how to float an egg in water, how to make an experiment with corn syrup, osmosis egg experiments, science projects with chickens, cool science experiments with eggs, raw egg & vinegar experiments, osmosis science activities for kids, density experiments for elementary, osmosis experiments with gummy bears, how to make a 20% sugar solution, density vs. concentration, science projects using gummy worms, how to make an egg float using salt for a science project.

• Oregon State University, Agriculture in the Classroom: Egg Science: Dissolution & Osmosis
• ILoveBacteria.com: Egg Osmosis
• Penn State Materials Research Institute, Education and Outreach Programs: Osmosis Eggs
• CSIRO: Easter Egg Eggs-periments for Kids
• Fermilab ARISE Project: Osmosis Egg Lab

About the Author

Joshua Bush has been writing from Charlottesville, Va., since 2006, specializing in science and culture. He has authored several articles in peer-reviewed science journals in the field of tissue engineering. Bush holds a Ph.D. in chemical engineering from Texas A&M University.

Photo Credits

Hemera Technologies/AbleStock.com/Getty Images

Find Your Next Great Science Fair Project! GO