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Study of Osmosis by Potato Osmometer

A study of osmosis can be done using a potato osmometer. Osmosis is a phenomenon in which water moves from high solvent to low solvent concentration. The movement of water occurs between two compartments, separated by a semipermeable membrane .

The cell membrane of living organisms behaves as a semipermeable or selective membrane. The permeability of a selective membrane differs based on the size, charge and mass of different molecules.

Biological membranes are impermeable to large biomolecules and polar molecules like ions. But, non-polar molecules (lipids) and small molecules (oxygen, carbon dioxide etc.) can cross the selective barrier.

Water is the solvent that travels down or up the cell concentration gradient through osmosis. We can study water diffusion by creating two compartments and a semipermeable membrane in between.

The difference in the concentration of solutes or solvents between two compartments is the driving force responsible for water movement. Here, we need to note that only solvents can pass the selective barrier, not solutes.

Thus, the diffusion or distribution of water is related to osmosis . This post describes the meaning, requirements, procedure and results of the potato osmometer experiment.

Content: Study of Osmosis by Potato Osmometer

Potato osmometer, materials required, precautions.

It is a common experiment to demonstrate both endosmosis and exosmosis using a potato. Using a potato Osmoscope, we can study osmosis in a living system.

Here, a potato is used because the porous outer surface of the potato acts as a selective membrane .

• The contents within the cell form one compartment.
• The solution surrounding the cell forms another compartment.

Thus, a selective membrane separates two compartments and allows the process of osmosis .

• High solvent concentration in the cell surrounding.
• Low solvent concentration in the cavity of potato tuber.

Following the rule of osmosis, water in the cell surrounding enters the tuber cavity via the cell membrane.

• High solvent concentration in the cavity of potato tuber.
• Low solvent concentration in the cell surrounding.

Following the rule of osmosis, water in the potato cavity enters the surrounding solution via the cell membrane.

• Peeled off potato
• Concentrated sugar solution
• Petri plate

Video: Study of Osmosis

To perform the potato osmometer experiment, we need to follow the given procedure:

• First, peel off the large-sized potato using a peeler or knife.
• Then cut the upper and lower portions of the peeled potato using a knife. Through this step, we can easily place the potato on the Petri plate.
• Using a knife, make a cavity from the centre of the potato deep into the bottom, leaving some space. Here, the bottom of the potato will function as a selective membrane.
• Then, keep the potato on the Petri plate.
• To study endosmosis , pour water into half of the Petri plate. Next, pour the concentrated sugar solution into half of the cavity created in the potato.
• To study exosmosis , add concentrated sugar solution on the Petri plate and water into the cavity of the potato tuber.
• Then, fix a pin into the potato tuber-A and B to mark the level of sugar solution and water added into the cavity.
• Leave the plate undisturbed for some time until you notice any change.

Observation

• Observe the level of sugar solution in the cavity of potato tuber-A.
• Notice the level of water in the cavity of the potato tuber-B.

Potato Osmosis Experiment Results

• The level of sugar solution in the cavity of potato tuber-A increases . It occurs because the water in the Petri plate will move towards the cell with a high solute or low solvent concentration. This experiment shows endosmosis , as water goes into the cell or potato tuber.
• In contrast, the level of water in the cavity of potato tuber-B decreases . Here, water in the cavity moves toward the solution in the Petri plate due to the high solute concentration in the surrounding. This experiment shows exosmosis as water leaves the cell or potato tuber.
• The cavity should be deep enough by leaving a minimum thickness at the bottom.
• The sugar solution should have a high osmotic concentration.

The water movement from the Petri plate to the potato cavity or vice versa is due to the difference in the solvent or solute concentration between the two compartments.

Related Topics:

• Germination of Plant
• Difference Between Root and Stem
• Nerve Impulse
• Ozone Formation
• Examples of Adsorption in Daily Life

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January 9, 2020

Make a Potato Shrink--with Saltwater

A water-moving science project from Science Buddies

By Science Buddies & Svenja Lohner

Create movement with salt! Learn how plant cells regulate water with an activity you can see--and feel.

George Retseck

Key Concepts Biology Osmosis Cells Chemistry Concentration Water transport

Introduction Have you ever wondered how plants "drink" water from the soil? Water uptake in plants is quite complicated. A process called osmosis helps the water move from the soil into the plant roots—and then into the plant's cells. In this activity you will see for yourself how you can make water move with osmosis!

Background Most water in the ground is not pure water. It usually contains dissolved mineral salts. Animals and plants need these salts (which include calcium, magnesium, potassium and the sodium you might be familiar with as table salt) to grow, develop and stay healthy. Different water sources carry different amounts of these salts. Nature wants to balance a system that is not balanced. So if you mix water with two different salt concentrations, the salts don't stay separated but spread out evenly through the solution until the salt concentration is the same throughout.

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You'll find a similar reaction if you separate two salt solutions with a semipermeable membrane. A semipermeable membrane is a type of barrier that only lets certain particles pass through while blocking others. This type of membrane usually lets water pass through but not the salts that are dissolved in the water. In this situation, because only water can move through this membrane, the water will start moving from the area of lower salt concentration (which has more water and less salt) to the area of higher salt concentration (which has less water and more salt). This water movement will only stop once the salt and water concentration on both sides of the membrane is the same.

The process of moving water across a semipermeable membrane is called osmosis. Plants use this process to their advantage for water uptake. They create an environment of high salt concentration in their root cells that are in contact with the soil. The cell walls act as a semipermeable membrane that only let water through. Because the water outside the root cells has a lower salt concentration, water starts moving into the root cells due to osmosis. The water entering the plant fills up the cells and can travel to the rest of the plant. Osmosis, however, works in both directions. If you put a plant into water with a salt concentration that is higher than the concentration inside its cells, water will move out of the plant to balance out the concentration difference. As a result the plant shrinks and eventually dies. You will see this effect with your own eyes in this activity using potatoes and different saltwater solutions.

Distilled water

Measuring cup with milliliters (mL)

Weight scale with gram measurements

Three plastic cups or glasses

At least three potatoes

Apple corer. (Alternatively, you can have an adult help you use a cutting board and knife.)

Knife (and an adult helper to help you use it)

Pen or pencil

Paper towels

Graphing paper (optional)

Other vegetable(s) or fruit (optional)

Preparation

Prepare three different saltwater solutions. Create labels for the three cups: "0 grams," "2 grams" and "4 grams."

To each of the cups add 100 mL of distilled water.

Weigh out 2 grams of table salt, and add it to the cup that says "2 grams." Then weigh out 4 grams of table salt, and add it to the cup labeled "4 grams." Use a spoon to mix the solutions until all the salt is dissolved.

Draw a table in which you can enter the starting measurements (length and diameter or width) and end measurements of each potato strip for every salt concentration (0, 2 and 4 grams).

Prepare at least three potato cores. Carefully push the corer all the way through the potato, and remove the core carefully so the potato piece stays intact. (Alternatively, you can have an adult help cut the potato into strips that all have the same dimensions.) The potato pieces should be at least one-half inch thick and two inches long. (Ideally you will be able to prepare nine matching cores or strips so you can test three pieces in each solution to compare the results thoroughly.)

Use a knife to carefully remove any potato skin from your cores, and rinse the cores quickly with water.

Use a ruler to ensure each potato piece is the same size (ideally to the millimeter). Carefully use a knife to trim any pieces as needed.

Measure the dimensions (length and diameter or width) of each potato strip in millimeters, and write the information in the table.

Optionally, you can also weigh each potato piece and record their weights.

Put one potato strip (or three if you made nine pieces) into each of the cups. While you do that feel the potato strips with your fingers and try to flex them a little bit. How do they feel? Are they easy to bend?

Start your timer for 30 minutes. Let the potato strips sit in the different solutions for the whole time. What do you think will happen to the strips in each of the cups?

After 30 minutes inspect the potato strips inside the solutions. Do you see any changes?

Take the potato strip(s) out of the "0 grams" cup and place on a paper towel. While doing that feel the potato pieces again and try to bend them slightly. How do they feel? Are they easier or more difficult to bend than before?

Use the ruler to measure the exact length and diameter or width (in millimeters) of each of the potato strips, and write the results in your table. What do you notice about the potato strip measurements? Optionally you can weigh these pieces and record their weights.

Next take the potato strips from the "2 grams" cup, and place them on a paper towel; as you do this feel them. Measure their lengths and diameters or widths. Write your results in the table. Optionally you can weigh these pieces and record their weights. What changed about these potato strips?

Repeat the same steps with the potato strips in the "4 grams" cup. Write your results in the table. Are your results for these similar or different compared with the other ones?

How did the feeling of the strips compare based on what solution they were in? Why do you think this is?

Compare the results in your table. How did the length and diameter or width of the potato strips change in each cup? What about the weights if you took them? Can you explain your results?

Extra: If you weighed each of your strips before and after soaking them, compare the weights. How does the mass of the potato strips change in each solution?

Extra: Leave the potato strips in the solutions for a longer time period. How do they look if you let them soak in the saltwater for one hour or overnight?

Extra : If you have graphing paper, make a graph of your results with the salt concentration on the horizontal axis and the potato strip length or diameter after soaking on the vertical axis. Draw two lines to make your graph. For the first, connect each of the data points you found. For the second, draw a horizontal line starting at the point on the vertical axis that shows the original length of your potato strip. Based on your graph can you find a salt concentration at which the potato strip length should not change at all?

Extra: How does the activity work with other vegetables or fruit? Try it to find out!

Observations and Results Did your potato strips shrink and expand? At the beginning all the potato strips should have had the same length and should have all felt the same. When you put them into the different solutions, however, this starts to change. Whereas the potato strips in the "0 gram" cup probably got larger in size, the other potato strips probably got shorter after leaving them in the saltwater for 30 minutes. (If you didn't see any significant changes after 30 minutes, leave the potato strips in the saltwater solutions longer.)

The shrinking and expanding of the potato strips is due to osmosis. Potatoes are made of cells, and their cell walls act as semipermeable membranes. The 0 grams solution contains less salts and more water than the potato cells (which have more salts and less water). To balance out these concentration differences, the water from the cup moves into the potato cells. The incoming water in the potato cells pushes on the cell walls and makes the cells bigger. As a result the whole potato strip gets bigger. The opposite is the case in the higher concentration salt solutions. If the salt concentration in the cup is higher than inside the potato cells, water moves out of the potato into the cup. This leads to shrinkage of the potato cells, which explains why the potato strips get smaller in length and diameter. Due to the shrinking of the potato cells the potato strip also becomes less rigid. If you bent the potato strips, you should have noticed that those that had been in the solution with the highest amount of salt were much easier to bend than the potato strips in the water without salt.

If you made the graph you probably noticed that there is a salt concentration at which the potato strip neither expands nor shrinks. This should be where your data curve and your start length line intersect. At this point the salt concentration inside the potato cells and inside the cup are the same. Because the concentrations are already balanced no water moves.

Cleanup Discard the saltwater solutions in the sink. Throw the potato strips into the compost, and clean up your workspace. You can cook with the other pieces of unused potato.

More to Explore Osmosis , from Biology Dictionary Do Fish Drink? from McGill University's Office for Science and Society Cucumber Chemistry: Moisture Capture with Desiccants , from Scientific American Suck It Up! How Water Moves Through Plants , from Science Buddies STEM Activities for Kids , from Science Buddies

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Science Experiments on the Osmosis of a Potato

Osmosis Experiments With Potatoes for Kids

Osmosis, the process in which solvent molecules move from an area of lower solute concentration to an area of higher solute concentration, can easily be demonstrated with potato experiments. Potatoes are full of both water and starch, and will gain water when immersed in watery solutions. Conversely, they will lose water when in concentrated solutions, such as those containing a great deal of starch. You can use potatoes to set up osmosis experiments for students of all ages and levels.

Potatoes in Saltwater

Cut a potato in two, and immerse one of the halves in a very salty solution of water — one containing a quarter cup of salt in a cup of water. Immerse the other piece in tap water containing no added salt. Leave both in their respective solutions for half an hour, then remove the potato halves from their solutions and observe their differences. The one in the salty solution will have shrunk, indicating that water is diffusing from a less concentrated solution to a more concentrated solution. The one in the tap water solution, in contrast, will actually swell slightly, indicating that it is taking in water.

Salt, Sugar and Pure Water

This experiment helps students to differentiate between different degrees of concentration gradients. Make one salt water solution, one sugar water solution, and for the third solution, simply use tap water. Make three thin potato slices — 1/2 cm thick. Place each potato slice into each of the solutions, and leave the slices in the solutions for a half hour.

Observe that the slice placed in salt is very flexible, while the slice placed in sugar is flexible, but less so. Since potatoes already contain sugar, less water will diffuse out of the potato placed in sugar water. The slice placed in water will be rigid, since it will absorb water.

Potato Lengths in Saline Solutions

Give your students potato "cylinders" that are uniform in length and size: for instance, you could cut them to be 70 mm in length and 7 mm in diameter. Make solutions of saline in three different concentrations, 20 percent, 0.9 percent and 0.1 percent. Have the students measure the lengths and diameters of the potato cylinders before and after soaking them in the saline solutions for half an hour. Then, have them calculate the changes in the lengths and diameters of the cylinders, and plot the saline concentrations versus the changes.

Potato Cube Weights

Cut potatoes into four groups of small, uniform cubes measuring 1/2 cm by 1/2 cm. Make four different solutions of sucrose: 10 percent, 5 percent, 1 percent and 0.01 percent. Weigh each group, on a mass balance, before immersing it in the appropriate sucrose solution for half an hour. After immersion, weigh each group again and have your students calculate the changes in the potato masses. Ask them to comment on why a group gained mass, lost mass or retained the same mass.

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• The Teachers Corner: Science Experiment--Osmosis

About the Author

Tricia Lobo has been writing since 2006. Her biomedical engineering research, "Biocompatible and pH sensitive PLGA encapsulated MnO nanocrystals for molecular and cellular MRI," was accepted in 2010 for publication in the journal "Nanoletters." Lobo earned her Bachelor of Science in biomedical engineering, with distinction, from Yale in 2010.

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Potato Osmosis Lab

Explore what happens to potatoes when you put them in a concentration of salt water and then pure water. Set up an osmosis potato lab and learn all about osmosis when you try this fun potato experiment with the kids. We are always searching for simple science experiments . Grab the free printable experiment below.

💡 What is Osmosis ? Learn more about osmosis through a variety of experiments.

Recommended Grade Level: 6th-8th Grades

• 2 tall glasses of distilled water (or regular)
• Free printable instructions (below)

INSTRUCTIONS:

STEP 1: Peel and then cut your potato into four equal pieces about 4 inches long and 1 inch wide.

STEP 2: Fill your glasses half way with distilled water, or regular water if no distilled is available.

STEP 3: Now mix 3 tablespoons of salt into one of the glasses and stir.

STEP 4: Place two pieces of potato into each glass and wait. Compare the potatoes after 30 minutes and then again after 12 hours.

What happened to the potato pieces? Here you can see how a potato can demonstrate the process of osmosis. Make sure to go back and read all about osmosis!

If you thought the salt water would have a higher concentration of solutes than the potato, and the distilled water would have a lower concentration you would be correct. The potato in the salt water shrinks because water moves from the potato into the more concentrated salt water.

In contrast, water moves from the less concentrated distilled water into the potato causing it to expand.

What Happens to a Potato in Salt Water?

The process of moving water across a semi-permeable membrane from a low concentrated solution to a high concentrated solution is called osmosis . A semi-permeable membrane is a thin sheet of tissue or layer of cells acting as a wall that allows only some molecules to pass through.

In plants, water enters the roots by osmosis. The plants have a higher concentration of solutes in their roots than in the soil. This causes water to move into the roots. The water then travels up the roots to the rest of the plant.

ALSO CHECK OUT: How Water Travels Through A Plant

Osmosis works in both directions. If you put a plant into water with a higher salt concentration than the concentration inside its cells, water will move out of the plant. If this happens then the plant shrinks and will eventually die.

Potatoes are a great way to demonstrate the process of osmosis in our potato osmosis experiment below. Discuss whether you think the potato or the water in each glass will have the greatest concentration of solutes (salt).

Which potato pieces do you think will expand and which will shrink in size as the water moves from a low concentration to a high concentration?

CLICK HERE TO GET YOUR FREE POTATO OSMOSIS EXPERIMENT!

More Osmosis Experiment Ideas

don’t stop with a potato osmosis lab; try one of these osmosis experiments to extend the learning.

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• Biology Article
• Study Of Osmosis By Potato Osmometer

Understanding Osmosis Using Potato Osmometer

To study by demonstrating the osmosis process by potato osmometer.

What is Osmosis?

Osmosis is the phenomena in which solvent molecules pass through a semi-permeable membrane from an area of higher concentration to an area of lower concentration. The process continues until the quantity of fluid is balanced or equalized in both regions, the region of higher concentration and the region of lower concentration of the semipermeable membrane. In other words, osmosis is the diffusion or movement of water from a region of higher water potential to a region of lower water potential.

In osmosis, what are solvent and solute?

The fluid that permeates through the semipermeable membrane is called the solvent, whereas the solute is the dissolved particles in the fluid.

What is the solution?

The mixture of solute and solvent form the solution.

List the different types of solutions.

The following are the types of solutions:

• Hypertonic solution – It is a solution with a high solute level. If living cells are placed in a hypertonic solution, because of lower concentration water moves out of the cell causing it to shrink and becomes plasmolyzed.
• Hypotonic solution – It is a solution with low concentration levels of solute. If living cells are placed in this solution, water passes into the cells because of higher water concentration in comparison to the cell causing the cells to swell and turn turgid.
• Isotonic solution – A solution is said to be isotonic if both solutions have an equal concentration of solute. If living cells are placed in an isotonic solution, no change is shown as there is the equal concentration on both the regions hence the cell retains its original shape.

Material Required

• A fresh large-sized potato tuber
• 20% sucrose solution
• Scalpel/blade
• A Bell pin needle that is labelled with a waterproof ink

• Slice the potato tuber into two equal halves with the help of a scalpel or a blade. The outer skin is to be peeled off. Since the tuber shape is irregular, slice the halves into squares
• From the mid-region of the tuber, scoop from the soft parenchyma, so as to form a tiny cavity of a square or a circular shape. At the base, the cavity prepared should have a minimum thickness.
• Fill up half the cavity with the freshly prepared 20% sugar solution. Into the cavity, fix a pin in a way that the mark is in the same line with the layer of the sucrose solution.
• Set up the osmometer in a Petri dish/beaker that is filled with water in a way such that 75% of the potato osmometer is immersed in water
• The set up should remain uninterrupted for close to 1 hour.
• Notice the sugar solution in the osmometer towards the end of the experiment
• Carry out the experiment with the help of water in the cavity and the sucrose solution in the petri dish/beaker.

Observation

After a period of time, within the osmoscope, the sugar solution rises and is seen coloured.

• An increase in the level of sucrose solution is observed in the osmometer. It is because of the entrance of water due to endosmosis from the beaker.
• Also, a water potential gradient is built between the sucrose solution in the external water and the osmometer.
• Though both the liquids are divided by living cells of the potato tuber, they allow the entrance of water into the sugar solution.
• This demonstrates the entrance of water into the sugar solution through the tissues of potato serving as a selectively permeable membrane.

Viva Questions

Q.1. What is plasmolysis?

A.1. It is a process, wherein the protoplasm of the plant cell turns round as a result of contraction when placed in a hypertonic solution due to exosmosis resulting in the decline in the tension of the cell wall.

Q.2. What is the significance of osmosis?

A.2. Osmosis maintains cell turgidity. It causes the transportation of nutrients and discharge of metabolic waste products. It preserves the interior environment of a living entity to maintain an equilibrium between the intracellular fluid levels and water.

Q.3. What is diffusion?

A.3. The movement of molecules from a region of higher concentration to a region of lower concentration. Osmosis is a type of diffusion.

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Osmosis Potato Experiment: DIY Science Project Ideas for Kids

Finished with your lesson on Osmosis but still confused? Then you need to perform this simple Osmosis experiment. All you need are some potato slices and water. Learn about osmosis with potato slices in this simple osmosis potato experiment. Performing science experiments for kids will enable them to understand challenging scientific concept they are learning in a much better way.

Step-by-Step Instructions on How to Perform Osmosis Potato Experiment

Osmosis is the process by which water or any other solvent moves towards a solution with a higher concentration through a semipermeable membrane. The molecules in the solution with a lower concentration move towards the solution with a higher concentration to equalize the concentration on both sides. Osmosis is how plants absorb water and nutrients from the soil.

A simple science experiment for kids like the Osmosis Potato Experiment helps kids understand the concept easily.

What You’ll Need?

If you leave cut slices of potatoes or apples or pears outside for a while, you’ll notice that they turn brown. Why do you think this discoloration occurs? When you cut these fruits or vegetables, it leaves the cells open. An enzyme present in the cells, polyphenol oxidase, reacts with the oxygen in the air and turns the fruit brown. But can you prevent the slices from turning brown and keep them fresher for longer? Let’s learn through this osmosis potato experiment.

Here is a list of things you’ll need to perform the experiment:

• 1 medium sized potato
• 2 – 4 tablespoons of salt
• Distilled water
• 2 medium sized mason jars or drinking glasses

How to Perform Osmosis Potato Experiment?

Follow these instructions to perform the experiment:

• Step 1: Peel and cut the potatoes so you have wedges that are neither too thick nor too thin. Ensure that the potato wedges are roughly the same size. Note down the color of the freshly cut potato wedges and how they feel when you touch them.
• Step 2: Pour 200ml of distilled water into one glass or jar. 
• Step 3: Into the second glass, pour 200ml of distilled water and add 2-4 tablespoons of salt. Stir it well until the salt is completely dissolved.
• Step 4: Add two potato wedges into each of the glasses and let them sit overnight.
• Step 5: The next day, you’ll notice a difference in both the glasses. The potato wedges in the glass with the unsalted water have become bigger, while the wedges in the salted water have shrunk slightly.
• Step 6: Take the potato wedges out of the unsalted water and try bending them. You’ll notice that it is firm and breaks but doesn’t bend. Additionally, it still has a white color like a freshly cut piece of potato.
• Step 7: Now take the potato wedges out of the salted solution and try to bend them. You’ll notice the wedges have turned brown and bend easily without breaking.

What You’ll See?

Once you’ve performed the experiment, help your child understand the science behind the osmosis experiment. Here are a few questions and answers that will help children understand the behavior of the potato wedges in the two different solutions.

• Why did the potato wedges in the glass with plain distilled water become bigger?

The potato wedges expand and become bigger because of osmosis. Potatoes are made of millions of cells and the cell walls act as a semipermeable membrane. The water molecules move into the potato through this membrane to balance the concentration levels. The water moving inside the potato cells causes it to expand and become bigger. 

• Why did the potato wedges in the glass with salt water shrink?

Again it’s because of osmosis. The salt solution has a higher concentration and the water inside the potato moves through the cell walls to balance the concentration in the saltwater. Since the water moves out of the potato wedge, it shrinks and becomes smaller. This is also the reason why the potato wedge in the salt solution becomes less rigid and bends easily.

• Why did the potato wedges in the salt solution change color?

The water moving out of the potato damages it’s cells, which causes them to release an enzyme called catechol oxidase. The enzyme in the potato cells reacts with the oxygen in the air and turns the wedges brown.

Other Way to Perform Osmosis Potato Experiment for Kids

Another cool way to see osmosis in action is to perform this experiment using grapes and raisins.

• 2 – 3 raisins
• 2 – 3 fresh grapes
• 3 – 4 tablespoons of sugar

Step-by-Step Guide on How to Perform Osmosis Potato Experiment

Follow these instructions to perform this experiment:

• Step 1: Add the 3 – 4 tablespoons of sugar into one glass of water and stir it until all the sugar is dissolved. Then add 2 -3 fresh grapes into the sugar solution.
• Step 2: Add 2 – 3 raisins to the second glass of water. Allow both glasses to sit for a few hours.
• Step 3: After a few hours, you’ll notice that the raisins in the plain water have plumped up almost as if they are grapes. The raisins have a higher concentration of sugar, so the water moves into the raisins to balance the amount of sugar. This causes the raisins to expand and plump up.
• Step 4: Meanwhile the grapes in the sugar solution have shrunk and almost look like raisins. The water surrounding the grapes has a higher concentration of sugar than water in the grape cells. So the water in the grape cells moves out to balance the level of sugar. This causes the grapes to shrink in size.

Can you use other vegetables or fruits to perform this experiment? Will sliced bananas or pineapples work the same way? The only way to know is to try. Looking for more cool science experiments to try with your kids? Check our kids learning section for more fun and informative science experiments.

Frequently Asked Questions on Osmosis Potato Experiment

What is osmosis.

Osmosis is the process by which a solution with a lower concentration moves towards a solution with a higher concentration through a semipermeable membrane to balance the levels of concentration.

Why does the potato in the salt solution shrink?

Potato cells also have water in them. The water in the potato tries to equalize the concentration by moving towards the saltwater. The loss of water causes the potato to shrink and also makes it bendy and less firm.

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Using Potatoes for Osmosis and Diffusion Labs

• Teach or illustrate multiple concepts
• Use simple consumable materials and readily available lab items
• Involve weighing, measuring and calculating
• Require the students to make a HAND-MADE graph
• Provide a perfect visual of the concepts I teach in the classroom
• Reinforce the use of lab equipment and proper laboratory skills
• Require the students to use critical thinking and problem solving skills
• Require students to closely examine the date in order to draw a conclusion

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Biology practicals

Investigating osmosis in potatoes, select lesson.

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Inheritance, variation and evolution

Homeostasis and response, bioenergetics, infection and response, organisation, cell biology, working scientifically, practical skills, explainer video, ​​in a nutshell.

By putting potato cylinders into different concentrations of sucrose solution, you will be able to investigate osmosis in a real-life example. Depending  on the water concentrations in the solutions , the potato cylinders will gain or lose mass, due to osmosis.

Equipment list

The following equipment list can be used to conduct an experiment to investigate osmosis in potato cylinders.

Experiment 1: Investigating osmosis in potatoes

​​experimental variables.

All experiments have three different variables: the independent, dependent and control variables. The independent variable is the one you change. The dependent variable is the one which depends on what has been changed, therefore it is the one that is measured. The control variable is one which has been kept the same.

Safety precautions

When carrying out experiments, it is very important to consider safety precautions. This is so you and others do not get hurt.

This is your instructions on how to complete the experiment.

This is how you can use your data to be able to form conclusions.

Your graph should show a negative correlation between sucrose solution concentration and percentage change in mass. As the sucrose concentration increases, the percentage change in mass increases. In the strongest sucrose concentration, the potato cylinder will have decreased its mass the most. This is because there is a greater concentration gradient between the potato cells which have a higher water potential, and the sucrose solution which has a lower water potential. As a result, a greater number of water molecules will move out of the potato cells by osmosis. This makes the potato cells flaccid and they will decrease their overall mass.

Once you have completed your experiment, it will be important to consider the quality of your data and how accurate your results are. Identify potential sources of random or systematic error and suggest possible improvements and further investigations. 

A limitation of this experiment could be that there are slight differences in the size of the potato cylinders. Therefore, for each sucrose concentration, the experiment should be repeated with several cylinders. By doing this, any anomalies can be identified and a mean value can be calculated. This will make the percentage change in mass more accurate.

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FAQs - Frequently Asked Questions

What are the control variables for the osmosis required practical for gcse biology.

The control variables for the osmosis required practical for GCSE biology include the volume of sucrose solution used and the dimensions of the potato cylinders.

What is the independent variable for the osmosis required practical for GCSE biology?

The independent variable for the osmosis required practical for GCSE biology is the concentration of sucrose solution.

What is an example of a hazard in the osmosis required practical for GCSE biology?

One of the hazards in the osmosis required practical is the scalpel. The scalpel may cut your skin. Be careful when picking up the scalpel and make sure to put it somewhere safe once you have finished using it.