potato osmometer experiment class 11

• 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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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
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Study of Osmosis by Potato Osmometer: Experiment & Viva

Muskan Shafi

Content Writer

Osmosis is the movement of  molecules of a solvent from a solution of low concentration to a solution of high concentration through a semi-permeable membrane.  Osmosis plays a significant role in plants, animals, and also in humans.

• Study of Osmosis by Potato Osmometer is a demonstration of osmosis in living plant cells .
• Potato Osmometer , also known as Potato Osmoscope is used to demonstrate the process of osmosis.
• The water from the surroundings moves into the cells of the potato through the semi-permeable plasma membrane .
• The water is transported from a region of higher concentration to a lower concentration within the potato cells .

Osmosis  helps the roots of plants to absorb water from the surroundings into the cell sap. It also helps in transporting water to higher parts of plants such as leaves, branches, fruits , flowers, etc.

Key Terms:  Osmosis, Potato Osmometer, Potato Osmoscope, Cells, Plasma Membrane, Solvent, Molecules, Exosomosis, Endosmosis

Study of Osmosis by Potato Osmometer

[Click Here for Sample Questions]

Osmosis is defined as the movement of molecules from a region of higher concentration to a lower concentration until the concentrations become equal on either side of the membrane.

• Osmosis can easily be demonstrated with the help of a  Potato Osmometer .
• It helps to study the phenomenon of osmosis in a living system.
• The experiment is used to demonstrate both endosmosis and exosmosis using a potato . 
• Potato is used in the experiment due to its porous outer surface acting as a selective membrane .

Read More: 

Aim of Experiment

To study the process of Osmosis by a Potato Osmometer.

Osmosis is the movement of water (or solvent ) molecules from the region of their higher concentration to the region of their lower concentration through a semipermeable membrane.   The process of osmosis continues until the quantity of fluid is equal in both regions, i.e. the region of higher concentration and the region of lower concentration.

• Osmosis is a special type of passive diffusion of only solvent molecules through a semi-permeable membrane.
• Semi-permeable Membrane is a kind of membrane that helps in the movement of solvents but prevents the movement of solute particles.
• The cell membrane of a living cell is semi-permeable in nature.

Types of Osmosis 

Osmosis can be categorized into two major types depending on the concentration of solvent inside the cell and outside the cell: 

• Exosomosis: It is the movement of water molecules out of the cell sap through the plasma membrane. It occurs when the solution outside the cell is hypertonic.
• Endosmosis: It is the movement of water molecules into the cell sap when the solution outside the cell is hypotonic in nature.

Important Terms Related to Osmosis 

• Solvent: It is the fluid that permeates through the semipermeable membrane and dissolves the solute.
• Solute: It is a substance that can be dissolved into a solution by a solvent. 
• Solution:  Solution is a homogeneous mixture of one or more solutes dissolved in a solvent. 

Osmotic Solutions

There are three different types of solutions during Osmosis: 

• Isotonic Solution: It is a solution that has the same concentration of solutes both inside and outside the cell . If living cells are placed in an isotonic solution, there is no change as there is an equal concentration in both regions. Thus, the cell retains its original shape.
• Hypertonic Solution: It is a solution that has a higher solute concentration outside the cell than inside . If living cells are placed in a hypertonic solution, water moves out of the cell because of lower concentration causing it to shrink and become plasmolyzed.
• Hypotonic Solution: It is a solution that has a higher solute concentration inside the cell than outside . If living cells are placed in a hypotonic solution, water moves into the cells due to higher water concentration in comparison to the cell. It causes the cells to swell and turn turgid.

Materials Required

To study Osmosis by Potato Osmometer, the following material is required: 

• Fresh Large Potato
• 20% Sucrose Solution
• Scalpel/Blade
• Bell Pin Needle labeled with a Waterproof Ink

Follow the given steps to study the phenomenon of Osmosis by Potato Osmometer: 

• Take a large and fresh potato and slice the potato tuber into two equal halves with the help of a scalpel or a blade.
• Peel off the outer skin and slice the halves into squares.
• S coop off the potato from the mid-region of the tuber to form a tiny cavity of a square or a circular shape.
• The cavity prepared should have a minimum thickness at the base. 
• Now, fill up the cavity with the freshly prepared 20% sugar solution halfway .
• Fix a pin in the cavity in a way that the mark is in the same line as the layer of the sucrose solution.
• Set up the prepared osmometer in a Petri Dish/Beaker filled with water such that 75% of the potato osmometer is immersed in water.
• The setup should be kept uninterrupted for up to 1 hour.
• Keep a note of the sugar solution in the osmometer towards the end of the experiment
• Lastly, carry out the same experiment with water in the cavity and the sucrose solution in the petri dish/beaker.

Observation

On observing the Potato Osmometer under the given setup, the following observations can be made: 

• The sugar solution rises and is seen colored within the osmoscope after an interval of time.
• The rise in the level of sugar solution in the cavity of the potato tuber indicates that the sugar solution has absorbed water from the petri dish .
• The two regions are separated from each other by a large number of cells.
• Cell membranes of different cells serve as one unit of a selectively semipermeable membrane.

Through the given experiment, the following conclusion is derived: 

• The level of sucrose solution is increased in the osmometer due to the entrance of water through endosmosis from the beaker.
• Cytoplasm of the cells of the tuber that lie between the sugar solution and the water of the petri dish act as a single semipermeable membrane.
• Water enters the sugar solution through the tissues of the potato serving as a selectively permeable membrane.

Precautions

The following precautions need to be taken care of during the experiment:

• The cavity should be vertical and deep so as to leave only a thin layer of tissue at the base.
• Peel off the skin of the tuber from the base and sides.
• Make a flat base so as to keep the potato tuber intact in water in the petri dish.
• The sugar solution should have a higher osmotic concentration as compared to the cell sap of the tuber cells.
• Marking of level with pin should be done carefully.

Check More: 

Things to Remember

• Osmosis is the movement of water molecules from a region of high concentration to a region of low concentration.
• Osmosis is of two types namely Exosmosis and Endosmosis .
• The solvent molecules move inside the cell in Endosmosis while the molecules move outside the cell in Exosmosis.
• Isotonic Solution , Hypertonic Solution , and Hypotonic Solution are the three types of Osmotic Solutions.
• In the potato osmometer experiment, the cells of the potato allow the entry of water molecules, i.e. the cells exhibit endosmosis.
• The water molecules reach the sugar solution kept inside the potato osmometer, causing a rise in the level of the sugar solution.
• Potato acts as a selectively permeable membrane due to its porous outer surface.

Viva Questions

Here are some important viva questions related to the experiment on ‘Study of Osmosis by Potato Osmometer’: 

Ques. What is Osmosis?

Ans. Osmosis is defined as the movement of molecules of a solvent from a solution of low concentration to a solution of high concentration through a semi-permeable membrane. 

Ques. What is Plasmolysis?

Ans. Plasmolysis   is a process in which the protoplasm of the plant cell turns round due to the contraction when placed in a hypertonic solution due to exosmosis leading to a decline in the tension of the cell wall.

Ques. Name the different types of Osmotic Solutions.

Ans. There are three types of Osmotic Solutions: 

• Isotonic Solution
• Hypertonic Solution
• Hypotonic Solution

Ques. State the Significance of Osmosis.

Ans. Osmosis is an integral process in plant cells as it helps to maintain cell turgidity. It helps in the transportation of nutrients and the discharge of metabolic waste products. Osmosis also maintains the internal environment of a living entity to maintain an equilibrium between intracellular fluid levels and water.

Ques. What is Diffusion? Is Osmosis diffusion only?

Ans.  Diffusion is defined as the movement of molecules from a region of higher concentration to a region of lower concentration. Yes, Osmosis is a special type of diffusion.

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Sample Questions

Ques. Define Osmosis. (3 Marks)

Ans.  Osmosis is a special type of diffusion that involves the movement of molecules from a region of higher concentration to a lower concentration through a semi-permeable membrane. 

• It continues until the quantity of fluid is balanced or equalized in both the regions, i.e. the region of higher concentration and the region of lower concentration.
• It is a passive process and occurs without any expenditure of energy. 
• Osmosis plays a significant role in plants, animals, and humans.

Ques. What will happen if a plant cell is kept in a solution of higher Water Potential? (2 Marks)

Ans.  If the solution has a higher water potential, then Endosmosis will occur. The solvent molecules move inside the cell and the cell becomes turgid or undergoes deplasmolysis. A solution that has a higher solute concentration inside the cell than outside is known as Hypotonic Solution. Endosmosis occurs in a Hypotonic Solution leading to the turgidity of cells.

Ques. What is a Semipermeable Membrane? (3 Marks)

Ans.   Semi-Permeable membrane is defined as a membrane through which only smaller molecules like water can pass but not the bigger molecules like solutes.

• It allows only the entry of solvent or selective solute substances.
• They appear to be continuous sheets or films but contain a network of sub-microscopic holes or pores through which smaller solvent molecules can pass easily. 
• Examples of semipermeable membranes include Cellulose acetate, potassium ferrocyanide, etc.

Ques. State the different types of Osmotic Solutions.  (3 Marks)

Ans. Osmotic Solutions are of three types namely: 

• Isotonic Solution: Isotonic Solution is a solution that has the same concentration of solutes both inside and outside the cell.
• Hypertonic Solution:  Hypertonic Solution is a solution that has a higher solute concentration outside the cell than inside.
• Hypotonic Solution: Hypotonic Solution is a solution that has a higher solute concentration inside the cell than outside.

Ques. What are the types of Osmosis? (3 Marks)

Ans.  Osmosis is classified into two types which are: 

• Endosmosis : During endosmosis, the solvent moves into the cell. When a cell is placed in a hypotonic solution, the water moves inside the cell and swells as the solute concentration of the surrounding solution is less than that inside the cytoplasm.
• Exosmosis : During exosmosis, the solvent moves out of the cell. When a substance is placed in a hypertonic solution, the solvent molecules move outside the cell and it becomes flaccid as the solute concentration of the surrounding solution is higher than that inside the cytoplasm.

Ques. Define an Osmotically Active Solution. (1 Mark)

Ans. Osmotically Active Solution is a solution that can cause an osmotic entry of water into it.

Ques. What is Turgidity in Osmosis? (1 Mark)

Ans. Turgidity is a condition of the cell under which it cannot absorb more water by osmosis when placed in a hypotonic solution.

Ques. Explain the Significance of Osmosis.  (3 Marks)

Ans. Osmosis is a very important phenomenon owing to the following reasons: 

• It influences the transport of nutrients and the release of metabolic waste products in Plants.
• It helps in the absorption of water from the soil and conducts it to the upper parts of the plant through Xylem.
• It maintains the balance between water and intercellular fluid levels, thus, stabilizing the internal environment of a living organism
• Osmosis maintains the turgidity of plant cells.
• It is a process through which plants are able to maintain their water content despite the constant water loss due to transpiration.

Ques. What will be the rate of osmosis if a 5% sugar solution is used in the Osmometer? (1 Mark)

Ans. The rate of osmosis in a 5% sugar solution in an osmometer will be low as osmosis is dependent upon the degree of reduction of free energy of one solvent over the other.

Ques. How does water from outside enter the Osmometer? Does it pass through the cells of the Tuber? (2 Marks)

Ans. The water enters the osmometer through the semipermeable membrane of the cells of the potato, which allows the entry of solvent or selective solute substances. The water passes through the cells of the tuber into the cavity. The cell membrane of different cells of both regions serves as one unit of a selectively semipermeable membrane.

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CBSE CLASS XII Related Questions

1. draw a well-labelled diagram of an antibody molecule., 2. is sex education necessary in schools why, 3. describe briefly the followings: origin of replication bioreactors downstream processing, 4. give three hypotheses for explaining why tropics show greatest levels of species richness., 5. all algae have.

• chlorophyll a and b
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6. Mention two strategies evolved to prevent self-pollination in flowers.

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What is osmosis? Explain the experiment with a diagram.

• Question Answer
• What is osmosis Explain the ex...

Repeaters Course for NEET 2022 - 23

The given figure shows set up of potato osmoscope experiment. Select the option that correctly identified the labels A, B and C. A-Unpeeled potato, B-Sugar solution, C-Water A-Unpeeled potato, B-Water, C-Sugar solution A-Peeled potato, B-Sugar solution, C-Water A-Peeled potato, B-Water, C-Sugar solution

In the given figure we can see that endosmosis has taken place because the water level rises from the one which was marked initially with the pin. a represents a field potato where the potato acts as an osmoscope through which osmosis occurs. the potato spl because the potato peel does not act as a semipermeable membrane and hence would prevent osmosis from occurring. for endosmosis to occur the solution kept inside the potato should be of higher concentration hence it is a sugar solution. similarly for and osmosis to occur potato should be kept in a solution of low concentration or plain water. water hence moves inside the potato as it contains a solution of higher concentration. so the correct option is ' a- peeled potato, b- sugar solution, c-water'..

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Teach With Fergy

Education Through Engagement and Application

Osmosis Demonstration – Osmosis and the Mighty Potato

By Fergy on September 19, 2016 1

Osmosis and the Mighty Potato – Classroom Inquiry and Demonstration

Osmosis is simply the diffusion of water molecules across a semi-permeable membrane. As is the case with diffusion, water molecules like to go from an area of high concentration to an area of low concentration.

This demonstration shows quantitively and qualitatively, the effects of osmosis. At the bottom you’ll find the results of the experiment I did in my class and trust me, the results are significant.

Materials needed: • A potato (or multiple if you students will also be doing the experiment) • A knife • A balance • 2 plates with lips to avoid spills • Tap Water (fresh water) • Salt

The Activity: 1. Have your students draw this chart.

2. Ask your students what they think will happen when you place a cut potato to two different environments. One in fresh water (tap water) and the other in salt water. Have them write it down in the ‘My Opinion’ column including why they think so. 3. Have your students share their answers with the person beside them. Each student should then write the combined opinion in the ‘Group Opinion’ column as they did before. 4. Lastly, have each group share their results with another group and write the consensus opinion in the ‘Shared Opinion’ column. 5. Weigh both cut potatoes and record the masses.

7. Once the time is up, take the potatoes out of the water, dry them, and place them on the scale. Compare their masses before and after.

Explanation: Water moves from high to low concentration in order to dilute any solutes (substances in the water). Salt is a solute and when you place the potato in the salt solution, you are exposing the potato to a much lower water concentration (high solute concentration) due to the solutes present. Although water moves into and out of the potato, there’s a net movement of water from inside the potato into the salt-water solution. Less water in the potato means less mass. When the potato is placed into the fresh water dish, there’s no difference in water concentration between the potato and the surrounding water environment, therefore, there’s no net movement of water. This leaves the potato with an equal mass before and after the experiment.

10. Have your students complete the last row using the information you provide in the explanation.

My Experimental Results: Trial #1 – Fresh water Potato

Initial mass – 288 g

Final mass – 298 g

Difference = 10 g increase = 3.4% INCREASE in mass

Trial #2 – Salt Water Potato

Initial mass – 305 g

Final mass -272 g

Difference = 33 g decrease = 11% LOSS in mass

As shown above, there was a significant difference in the two trials. The fresh water potato gained some mass (small amount of water absorbed), while the salt water potato lost 11% of its mass. The loss in mass was due to water leaving the potato to balance the water concentrations as the environment was rich with salt.

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Reader Interactions

July 1, 2017 at 3:06 pm

I think this is a great activity and I think it will be easier to execute over doing the dialysis tubing. I also think the students will like it more because potatos are “real” to them, not dialysis tubing.

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Experiments on Osmosis (With Diagram)

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The below mentioned article includes a list of four simple experiments on osmosis.

1. Experiment to demonstrate the osmosis by using sheet of cellophane or goat bladder:

Requirements:

Beaker, thistle funnel, goat bladder or sheet of cellophane, thread, water and sugar solution.

1. Cover the lower opening of the glass tube with the goat bladder or sheet of cellophane and tie it with the thread.

2. Fill in the interior of the tube with molasses, a concentrated sugar solution in water.

3. Place the whole apparatus in a beaker containing water, preferably distilled water.

4. Note the level of the water in the thistle funnel and keep the apparatus to note the results.

Observations:

Level of the water in the thistle funnel increases (Fig.2).

1. Movement of water through the goat bladder or cellophane sheet into the thistle funnel takes place.

2. Water concentration in beaker is 100% while in the sugar solution it is less than this, and, therefore, the water from the region of higher concentration moves towards the region of lower concentration. The movement is through a semipermeable membrane and so the experiment shows the phenomenon of osmosis.

3. The force, with which the solution level in the tube increases, arises from the pressure exerted by the diffusion of water molecules into the tube. This pressure is called osmotic pressure.

4. Stability of the water level in the funnel indicates that water concentration in both the beakers as well as funnel is same and thus osmosis stops.

2. Experiment to demonstrate osmosis with the help of potato osmometer:

Petri-dish, water, potato, sugar solution, cork and capillary tube.

1. Take a potato tuber, remove its outer covering from one end and cut the same end flat.

2. Scoop out a cavity from the other end of the tuber running almost upto the bottom.

3. Fill the cavity with the sugar solution and fit an airtight cork fitted with a capillary tube on the upper end of the cavity (fig. 3).

4. Place the capillary- fitted potato tuber in the water- filled petri-dish.

5. Mark the solution level in the tube and watch the experiment for some time.

After some time the level of the solution in the tube increases. Mark the level of solution when it stops to move.

The level in the capillary tube increases because of the fact that osmotic pressure of the sugar solution is higher than that of the water, and the water moves through the semipermeable membrane of potato from petri-dish into the cavity. So the experiment shows that phenomenon of osmosis.

3. Experiment to demonstrate the osmosis by the egg osmometer:

Egg membrane, dilute HCI, water through, graduated tube, sugar solution and stand.

1. Prepare an egg membrane by carefully removing waterproof shell of egg with the help of dissolving it away in dilute HCI.

2. Remove all the fat and protein-containing yellow material of the egg by making a hole on its one end.

3. Fill the sugar solution in the egg membrane through the hole and fit a graduated tube in the hole.

4. Place the complete apparatus in a water-filled trough (Fig. 4).

5. Note the level of sugar solution in the graduated tube and keep the apparatus undisturbed for some time.

Level of the sugar solution increases in the tube.

The level in the tube increases because of the fact that osmotic pressure of the sugar solution in the egg membrane is higher than that of water, and so the water from the trough passes through the egg membrane into the sugar solution thus increasing its level. Egg membrane is a semipermeable membrane.

4. Experiment to demonstrate the phenomenon of exosmosis and endosmosis:

Potato tubers (2), knife, conc. sugar solution, water, pin, beakers (2).

1. Remove the outer skin of the tubers and cut their one end flat with a sharp knife.

2. Scoop out a cavity from the other end of the tuber running almost upto the bottom as in experiment No. 14.

3. Fill the concentrated solution of sugar in the cavity of one tuber, and water in the other.

4. Mark the level of the sugar solution and water in the cavities with the help of pins.

5. Place the potato containing sugar solution in a beaker containing water, and the another potato containing water in its cavity in the beaker containing sugar solution (Fig. 5).

6. Keep and observe experiment for some time.

The level in the cavity containing sugar solution increases while the level decreases in the another tuber, i.e., in the cavity filled with water.

The level of the sugar solution in the first tuber increases because of the fact that water moves from the beaker into the cavity through the semipermeable membrane of potato. Thus it shows the phenomenon of endosmosis.

The level of the water in the second tuber decreases because of the fact that water moves from the cavity into the beaker through the semipermeable membrane of potato tuber. Thus it shows the phenomenon of exosmosis.

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• Experiment on Osmosis in Potatoes | Botany
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Experiment , Chemistry , Osmosis , Experiments on Osmosis

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