diffusion in potato experiment

• 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.

For more information on related biological concepts and experiments, please register at BYJU’S.

Related Links:

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

Visit BYJU’S for all Biology related queries and study materials

Your result is as below

Request OTP on Voice Call

Leave a Comment Cancel reply

Your Mobile number and Email id will not be published. Required fields are marked *

Post My Comment

Good Thank you BYJU’S!!

Search My Blog

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

No comments:

Post a comment.

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 ⋅

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.

Related Articles

Osmosis science activities for kids, ib group 4 project ideas, fun science experiments with potatoes, science projects for cut flowers, high school science experiments with plants, sugar & salt crystal science projects, how to grow a potato in water for a science project, ideas for a science fair project using kool-aid, science fair on how vitamin c & ibuprofen affect plant..., how to measure solubility for a science project, activities on conductivity, water evaporation science fair projects, how to make a five percent solution with salt, how to make crystals out of salt, science projects and research with salt, sugar, water..., polarity projects using a potato, how to make polymer crystals, osmosis egg experiments, how to make a saltwater battery for a science project.

• 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.

Find Your Next Great Science Fair Project! GO

The Osmosis Lab

Introduction: The Osmosis Lab

The project idea is to apply an experiment that circulates around diffusion which is the diffusion of water molecules through a membrane which is the potato cores in this experiment. The aim of this project is to find the effect of the sucrose concentration on the mass of the potato. It's considered an essential project because it demonstrates new ideas about a lesson in science which is diffusion.

Step 1: Problem or Question

The experiment was about measuring the mass of potato cores before and after placing them inside a tube of distilled water, and 5 tubes that consist of differently concentrated solutions of sucrose in water. The research question that this experiment circulates around is how the increase in the concentration of sucrose in water affects the mass of the potato ?. Accordingly, the goal of this experiment is to discover the effect of differently concentrated solutions on the mass of the potato cores.

Step 2: Hypothesis

If the concentration of sucrose increases, then the mass of the potato cores will increase accordingly and this can be proved in the process of osmosis. In which osmosis occurs to balance between the concentration of water in a substance and in the air which adds water to air and this makes the air denser. Moreover, the potato cores mass will increase due to adding more amounts of sucrose, because when adding more amounts of sucrose the potato will swallow more sucrose which has a certain mass that will be added to the potato.

Step 3: Variables

Variables are the factors in an experiment that can be controlled, changed (affected), or measured in an experiment. The variables are divided into three different types which are the controlled variable, dependent variable, and the independent variable.

Dependent variable:

The mass of the potato cores is the dependent variable because it gets affected due to the change in the concentration of sucrose. The mass of the potato cores can be found using the weight balance which gives the mass of the potato cores in grams.

Independent variable: The concentration of sucrose is the independent variable in the experiment because the higher concentration of sucrose increases the mass of the potato cores. Moreover, the concentration of sucrose changes as the potato cores get exposed to different concentrations of sucrose which are 0.2, 0.4,0.6, 0.8, and 1.0 in order to determine the relationship between the concentration of sucrose and the potato cores mass.

Controlled variable: The water is the controlled variable because it stays constant and can be controlled by adding more amounts of water or fewer amounts of water into the testing tubes.

Step 4: Background Research

The mass is one of the factors that can be recognized from the background research because it's an essential part of many experiments. Mass is defined as a unit that measures the size of an object as weight in grams (for low weight objects), in kilograms for heavy objects, and in ton for superheavy objects such as machines. In addition, is an essential part of this experiment which is considered as a type of diffusion that can be defined as the movement of water molecules from areas of higher concentration to areas of lower concentration through a membrane. Osmosis is very similar to the other types of diffusion, in which there is only one factor that makes it different or special which is the fact that it's applied only for water molecules.

Step 5: Materials

Potato coring device

6 testing tubes

Distilled water

Weight balance

0.2 ml of the solution in water

0.4 ml of the solution in water

0.6 ml of the solution in water

0.8 ml of the solution in water

1.0 ml of the solution in water

Safety equipment: safety goggles and the lab coat

Step 6: Procedure

Before starting the experiment there were tools that were required for safety precautions which are the safety goggles the lab coat, and gloves.

-First, prepare the materials that are required for the experiment.

-Second, pour distilled water in a beaker then pour it into the testing tube until it's filled up and name it as distilled water.

-Third, pour water into the beaker then pour the water with a concentration of 0.2 ml of sucrose into the second testing tube and name it as s1.

-Fourth, pour water into the beaker then pour the water with a concentration of 0.4 ml of sucrose into the third testing tube and name it as s2.

-Fifth, pour water into the beaker then pour the water with a concentration of 0.6 ml of sucrose into the fourth testing tube and name it as s3.

-Sixth, pour water into the beaker then pour the water with a concentration of 0.8 ml of sucrose into the fifth testing tube and name it as s4.

-Seventh, pour water into the beaker then pour the water with a concentration of 1.0 ml of sucrose into the sixth testing tube and name it as s5.

-Eighth, Use the coring device to cut the potato into 12 small pieces, then remove the potato skin using the razor blade.

-Ninth, measure the mass of two potato cores using the weight balance.

-Tenth, place 2 potato cores in each testing tube and check them after 24 hours.

-Eleventh, remove the potato cores from the testing tubes and measure the weight of each two.

-Finally, record the observations and take notes.

Step 7: Data Table

Step 8: Graph

Step 9: Data Analysis

It's clearly noticeable that there is a positive relationship between the solution's concentration and the mass of the potato in which as the solution's concentration increases, the mass of the potato cores increases. In other words, the mass of the potato cores (dependent variable) depends on the solution's concentration (Independent variable) to change (positively because it increases) and throw out the experiment. For instance, when the potato cores were exposed to the first solution (0.2 g/l) the potato cores had a mass of 10.68, while when the potato cores were exposed to another solution of 0.4 g/l it had a mass of 10.72.

Step 10: Results

The results of the experiment were as the following, the potato cores which were exposed to the first solution with a concentration of 0.2 g/l had a mass of 10.68, the potato cores which were exposed to the second solution with a concentration of 0.4 g/l had a mass of 10.72, while the potato cores which were exposed to the third solution with a concentration of 0.6 g/l had a mass of 10.76. Furthermore, the potato cores which were exposed to the fourth solution with a concentration of 0.8 had a mass of 10.80, finally, the potato core that were exposed to the fifth and lastsolution with a concentration of 1.0 had a mass of 10.84.

Step 11: Conclusion

Since the data shows that the potato cores which were exposed to solution 1 which has a concentration of 0.2 g/l had a new mass of 10.68 g, the potato cores which were exposed to solution 2 which has a concentration of 0.4g/l had a new mass of 10.72 g, and the potato cores which were exposed to the solution 3 which has a concentration of 0.6 g/l had a new mass of 10.76g, the potato cores which were exposed to the solution 4 which has a concentration of 0.8 g/l had a new mass of 10.80 and the potato core which were exposed to the solution 5 which has a concentration of 1.0 had a new mass of 10.84. For that reason, the hypothesis is correct, In which each time the concentration increases, the mass of the potato cores increases accordingly as it has been noticed in the data.

Step 12: Application

This type of research is essential for humanity because it plays an essential role in plant's lives which are an essential factor for human's lives as well, as they provide the necessities for breathing (oxygen) and food. In which osmosis occurs in plants to balance between the amount of water in the air and in the plant in which the plants have higher amounts of water than air, so water diffuses into the air until the amount of water in both the plant and air is equal. But if the plant is not watered to replace the lost amount of water, it wouldn't survive so obviously it will die. This topic could be practiced in various experiments such as gummy bears and sugar cubes by exposing them to solutions with different concentrations.

Step 13: Evaluation

I utilized Communication skills by giving an introductory video that includes the necessary means to present my idea in the project clearly which included a background related to the topic. In addition, I added some photos that clearly showcase the part of the project that I am discussing (in the instructable).

Step 14: List of Refrences

Images used:

https://www.google.com/search?q=problem&safe=stric...

https://www.google.com/search?q=hypothesis&safe=st...

https://www.google.com/search?q=variables&safe=str...

https://www.google.com/search?q=background+researc...

https://www.google.com/search?q=materials+in+exper...

https://www.google.com/search?q=procedure&safe=str...

https://www.google.com/search?q=data+analysis&safe...

https://www.google.com/search?q=osmosis+lab+&tbm=i...

https://www.google.com/search?q=real+life+applicat...

https://www.google.com/search?q=evaluation&tbm=isc...

https://www.google.com/search?q=results&safe=stric...

https://www.google.com/search?q=references&safe=st...

The experiments data:

Due to the current situation and Covid-19, I couldn't collect the required materials to perform the experiment for that reason, I relied on data derived from another person's experiment.

Recommendations

Puzzles and Games Contest

Pets and Animals Contest

Paper and Cardboard Contest

• Educational toys for children 0 - 12 Years

• Search for:

No products in the cart.

Return to shop

Salty Potato Experiment: Get to Know Osmosis

Christopher Leiknes , Scientist Factory

Nature always tries to equalize differences. We experience this, for instance, when someone makes pancakes and the whole house smells delicious. The aroma molecules spread throughout the air, but diffusion doesn’t only happen in the air. It happens in plants and animals as well. Try and see for yourself.

Instructions

• Cut the potato into two equal halves
• Fill two bowls wit water. Add 2 tablespoons of salt to one of the bowls
• Put the potato halves into one bowl each and let them sit for 20 minutes
• Remove the botato halves and look at them. What has happened?

What happens?

The potato halves are no longer the same size. When we add salt, we create an imbalance. There’s a higher salt concentration in the water than in the potato. Water is sucked out of the potato to equalize the salt concentration. It therefore shrinks. A similar thing happens when we swim in freshwater. There’s less salt in the water than in our bodies. Water is sucked out of our bodies, and our fingers become pruned.

The opposite happens if you place an egg in vinegar. The vinegar will firstly dissolve the shell. Then water will penetrate the egg through its membrane, causing the egg to expand. There is more salt inside the egg than in the vinegar, and the opposite happens. It takes a few days.

Christopher Leiknes, Scientist Factory Nature always tries to equalize differences. We experience this, for instance, when someone makes pancakes and the whole house smells delicious. The aroma molecules spread throughout the air, but diffusion doesn’t only happen in the air. It happens in plants and animals as well. Try and see for yourself. Equipment 1….Click to read more

• Advent calendar
• Chemistry kits
• Educational toys
• Mathematics
• Experiments

Username or email address  *

Password  *

Remember me Log in

Lost your password?

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons

Margin Size

• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

Module 4: Diffusion and Osmosis

• Last updated
• Save as PDF
• Page ID 24539

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

\( \newcommand{\Span}{\mathrm{span}}\)

\( \newcommand{\id}{\mathrm{id}}\)

\( \newcommand{\kernel}{\mathrm{null}\,}\)

\( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\)

\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\)

\( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

\( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vectorC}[1]{\textbf{#1}} \)

\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

Introduction:

The cell membrane plays the dual roles of protecting the living cell by acting as a barrier to the outside world, yet at the same time it must allow the passage of food and waste products into and out of the cell for metabolism to proceed. How does the cell carry out these seemingly paradoxical roles? To understand this process you need to understand the makeup of the cell membrane and an important phenomenon known as diffusion.

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration due to random molecular motion. All atoms and molecules possess kinetic energy, which is the energy of movement. It is this kinetic energy that makes each atom or molecule vibrate and move around. (In fact, you can quantify the kinetic energy of the atoms/molecules in a substance by measuring its temperature.) The moving atoms bounce off each other, like bumper cars in a carnival ride. The movement of particles due to this energy is called Brownian motion. As these atoms/molecules bounce off each other, the result is the movement of these particles from an area of high concentration to an area of low concentration. This is diffusion. The rate of diffusion is influenced by both temperature (how fast the particles move) and size (how big they are).

Part 1: Brownian Motion:

In this part of the lab, you will use a microscope to observe Brownian motion in carmine red powder, which is a dye obtained from the pulverized guts of female cochineal beetles.

• Glass Slide
• Carmine Red Powder
• Obtain a microscope slide and place a drop of tap water on it.
• Using a toothpick, carefully add a very minuscule quantity of carmine red powder to the drop of water and add a coverslip.
• Observe under scanning, low, and then high power.

Lab Questions:

1. Describe the activity of the carmine red particles in water.

2. If the slide were warmed up, would the rate of motion of the molecules speed up, slow down, or remain the same? Why?

Part 2: Diffusion across a Semipermeable Membrane

Because of its structure, the cell membrane is a semipermeable membrane. This means that SOME substances can easily diffuse through it, like oxygen, or carbon dioxide. Other substances, like glucose or sodium ions, are unable to pass through the cell membrane unless they are specifically transported via proteins embedded in the membrane itself. Whether or not a substance is able to diffuse through a cell membrane depends on the characteristics of the substance and characteristics of the membrane. In this lab, we will make dialysis tubing “cells” and explore the effect of size on a molecule’s ability to diffuse through a “cell membrane.”

The following information might be useful in understanding and interpreting your results in this lab:

• Atomic formula: C 20 H 14 O 4
• Atomic mass: 318.32 g/mol
• Color in acidic solution: Clear
• Color in basic solution: Pink
• Atomic formula: I or I2
• Atomic mass: 126 g/mol
• Atomic formula: (C 6 H 10 O 5 )n
• Atomic mass: HUGE!
• Color in Iodine: Bluish
• Atomic formula: NaOH
• Atomic mass: 40.1 g/mol
• Acid/Base: Base
• 2 pieces of dialysis tubing
• Phenolphthalein
• Starch solution
• Using a wax pencil, label one beaker #1. Label the other beaker #2.
• Fill beaker #1 with 300 ml of tap water, then add 10 drops of 1 M NaOH. Do not spill the NaOH—it is very caustic!
• Fill beaker #2 with 300 ml of tap water, then add iodine drops drop by drop until the solution is bright yellow.
• Now prepare your 2 dialysis tubing “bags.” Seal one end of each dialysis tube by carefully folding the end “hotdog style” 2 times, then “hamburger style” 1 time. Tie the folded portion of the tube securely with string. It is critical that your tubing is tightly sealed, to prevent leaks.
• Add 10 ml of water and three drops of phenolphthalein to one of your dialysis tube bags. Seal the other end of the bag by carefully folding and tying as before.
• Thoroughly rinse the bag containing phenolphthalein, then place it in into the beaker containing the NaOH.
• Add 10 ml of starch solution to the other dialysis tube. Again seal the bag tightly and rinse as above. Place this bag containing the starch solution into beaker #2.
• Let diffusion occur between the bags and the solutions in the beakers.
• After 10 minutes, observe the color changes in the two bags and the external solutions. Draw a picture of each system below.

Record the colors (below) and label contents inside and outside the bags (above):

1. Which substance diffused across the membrane in beaker #1? How do you know?

2. Which substance diffused across the membrane in beaker #2? How do you know?

3. Why might some ions and molecules pass through the dialysis bag while others might not?

Part 3: Osmosis and the Cell Membrane

Osmosis is the movement of water across a semipermeable membrane (such as the cell membrane). The tonicity of a solution involves comparing the concentration of a cell’s cytoplasm to the concentration of its environment. Ultimately, the tonicity of a solution can be determined by examining the effect a solution has on a cell within the solution.

By definition, a hypertonic solution is one that causes a cell to shrink. Though it certainly is more complex than this, for our purposes in this class, we can assume that a hypertonic solution is more concentrated with solutes than the cytoplasm. This will cause water from the cytoplasm to leave the cell, causing the cell to shrink. If a cell shrinks when placed in a solution, then the solution is hypertonic to the cell.

If a solution is hypotonic to a cell, then the cell will swell when placed in the hypotonic solution. In this case, you can imagine that the solution is less concentrated than the cell’s cytoplasm, causing water from the solution to flow into the cell. The cell swells!

Finally, an isotonic solution is one that causes no change in the cell. You can imagine that the solution and the cell have equal concentrations, so there is no net movement of water molecules into or out of the cell.

In this exercise, you will observe osmosis by exposing a plant cell to salt water.

Prediction:

What do you think will happen to the cell in this environment? Draw a picture of your hypothesis.

• Elodea Leaf
• Microscope Slide
• 5% NaCl solution
• Remove a leaf from an Elodea plant using the forceps.
• Make a wet mount of the leaf. Use the pond water to make your wet mount.
• Observe the Elodea cells under the compound microscope at high power (400X) and draw a typical cell below.
• Next, add several drops of 5% salt solution to the edge of the coverslip to allow the salt to diffuse under the coverslip. Observe what happens to the cells (this may require you to search around along the edges of the leaf). Look for cells that have been visibly altered.

Draw a typical cell in both pond and salt water and label the cell membrane and the cell wall.

What do you see occurring to the cell membrane when the cell was exposed to salt water? Why does this happen?

Describe the terms hypertonic, hypotonic, and isotonic.

How would your observations change if NaCl could easily pass through the cell membrane and into the cell?

Part 4: Experimental Design

You and your group will design an experiment to determine the relative molecular weights of methylene blue and potassium permanganate. You may use a petri dish of agar, which is a jello-like medium made from a polysaccharide found in the cell walls of red algae. You will also have access to a cork borer and a small plastic ruler.

• 1 Petri Dish of Agar
• Methylene Blue
• Potassium Permanganate

Your experiment design should include all of the following portions:

• Experimental design
• Conclusions
• Further Questions/Other Comments

Licenses and Attributions

CC licensed content, Original

• Biology Labs. Authored by: Wendy Riggs . Provided by: College of the Redwoods. Located at: http://www.redwoods.edu . License: CC BY: Attribution

Public domain content

• Osmotic pressure on blood cells diagram. Authored by: LadyofHats. Located at: https://commons.wikimedia.org/wiki/File:Osmotic_pressure_on_blood_cells_diagram.svg . License: Public Domain: No Known Copyright

Practical: Investigating Diffusion & Osmosis ( Edexcel IGCSE Biology )

Revision note.

Biology Lead

Practical: Factors that Influence Diffusion

• Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration
• Temperature
• Surface area
• Concentration gradient
• Diffusion distance
• Beetroot cells contain a dark purple-red pigment
• Heating above 45℃ can damage the cell membrane meaning that the pigment can leak out
• The speed at which this pigment leaks out of the cell tells us about the rate of diffusion

Investigating the effect of temperature on diffusion

• Cork borer (optional)
• Cutting board
• Water baths
• The pieces must have the same dimensions so that they all have equal surface areas and volumes , as these factors could affect the rate at which the pigment leaks out
• A cork borer can also be used, as long as the cores are cut to the same length
• To remove any pigment released during cutting
• Put 5 cm 3 of water into 2 test tubes labelled A and B
• Keep test tube A at room temperature and transfer test tube B to a hot water bath at 90℃
• Leave the test tubes for 2 minutes, then add a piece of beetroot into each test tube
• After 10 minutes, observe the colour of the liquid in both test tubes

Results and Analysis

• You should notice that at the higher temperature , more of the pigment has leaked out of the beetroot
• The cell membrane of the beetroot cells has become damaged so more pigment can leak out
• At higher temperatures, particles have more kinetic energy , this results in the faster movement of particles compared to when they have less energy

Investigating the effect of temperature on diffusion in beetroot

Limitations

• Solution: cut the beetroot as accurately as possible using a knife and ruler , and repeat each investigation several times to find a mean
• Solution: conduct several repeats , using different parts of the beetroot and find a mean
• Solution: Set up 5 test tubes in water baths at different temperatures (e.g. 10℃, 20℃, 30℃, 40℃, 50℃)
• Solution: use a colorimeter to measure how much light is absorbed as it passes through each of the five samples of coloured liquid

Applying CORMS to practical work

• When working with practical investigations, remember to consider your CORMS evaluation

CORMS evaluation

• C - We are changing the temperature of the environment
• O - The beetroot cubes will all be taken from the same beetroot or beetroot of the same age
• R - We will repeat the investigation several times to ensure our results are reliable
• M1 - We will observe the colour change of the liquid
• M2 - ...after 10 minutes
• S - We will control the volume of water used, the dimensions of the beetroot cubes and each cube must be blotted before it is weighed each time

Practical: Factors that Influence Osmosis

• Osmosis is the diffusion of water molecules from a dilute solution (high concentration of water) to a more concentrated solution (low concentration of water) across a partially permeable membrane

Osmosis in cells

• We can investigate osmosis using cylinders of potato and placing them into distilled water and sucrose solutions of increasing concentration
• Sucrose solutions (from 0 Mol/dm 3 to 1 mol/dm 3 )
• Paper towels
• Test tube rack
• Prepare a range of sucrose (sugar) solutions ranging from 0 Mol/dm 3 (distilled water) to 1 mol/dm 3
• Set up 6 labelled test tubes with 10cm 3  of each of the sucrose solutions
• Using the knife, cork borer and ruler, cut 6 equally-sized cylinders of potato
• Blot each one with a paper towel and weigh on the balance
• Put 1 piece into each concentration of sucrose solution
• After 4 hours, remove them, blot with paper towels and reweigh them

Experimental method for investigating osmosis in potato cylinders

Results and analysis

• The percentage change in mass can be calculated for each piece of potato

Calculating percentage change in mass

• The potato cylinder in the distilled water will have increased its mass the most as there is a greater concentration gradient in this tube between the distilled water (high water potential) and the potato cells (lower water potential)
• This means more water molecules will move into the potato cells by osmosis , pushing the cell membrane against the cell wall and so increasing the turgor pressure in the cells which makes them turgid - the potato cylinders will feel hard
• The potato cylinder in the strongest sucrose concentration will have decreased its mass the most as there is a greater concentration gradient in this tube between the potato cells (higher water potential) and the sucrose solution (lower water potential)
• This means more water molecules will move out of the potato cells by osmosis , making them flaccid and decreasing the mass of the cylinder - the potato cylinders will feel floppy
• If looked at underneath the microscope, cells from this potato cylinder might be plasmolysed , meaning the cell membrane has pulled away from the cell wall

Plasmolysed red onion cells

• If there is a potato cylinder that has not increased or decreased in mass, it means there was no overall net movement of water into or out of the potato cells
• This is because the solution that the cylinder was in was the same concentration as the solution found in the cytoplasm of the potato cells, so there was no concentration gradient
• Solution: for each sucrose concentration, repeat the investigation with several potato cylinders. Making a series of repeat experiments means that any anomalous results can be identified and ignored when a mean is calculated

Applying CORMS evaluation to practical work

• C - We are changing the concentration of sucrose solution
• O - The potato cylinders will all be taken from the same potato or potatoes of the same age
• M1 - We will measure the change in mass of the potato cylinders
• M2 - ...after 4 hours
• S - We will control the volume of sucrose solution used, the dimensions of the potato cylinders and each cylinder must be blotted before it is weighed each time

Questions involving osmosis experiments are common and you should be able to use your knowledge of these processes to explain the results .Don’t worry if it is an experiment you haven’t done – simply figure out where the higher concentration of water molecules is – this is the solution with the higher water potential - and explain which way the molecules move due to the differences in water potential .

You've read 0 of your 0 free revision notes

Get unlimited access.

to absolutely everything:

• Downloadable PDFs
• Unlimited Revision Notes
• Topic Questions
• Past Papers
• Model Answers
• Videos (Maths and Science)

Join the 100,000 + Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

Home — Essay Samples — Science — Experiment — Concluding Insights from the Potato Experiment

Concluding Insights from The Potato Experiment

• Categories: Cell Experiment Osmosis

About this sample

Words: 598 |

Published: Jun 13, 2024

Words: 598 | Page: 1 | 3 min read

Table of contents

Introduction, body paragraph.

Cite this Essay

Let us write you an essay from scratch

• 450+ experts on 30 subjects ready to help
• Custom essay delivered in as few as 3 hours

Get high-quality help

Verified writer

• Expert in: Science

+ 120 experts online

By clicking “Check Writers’ Offers”, you agree to our terms of service and privacy policy . We’ll occasionally send you promo and account related email

No need to pay just yet!

Related Essays

2 pages / 706 words

4 pages / 1720 words

2 pages / 1108 words

4 pages / 2102 words

Remember! This is just a sample.

You can get your custom paper by one of our expert writers.

121 writers online

Still can’t find what you need?

Browse our vast selection of original essay samples, each expertly formatted and styled

Related Essays on Experiment

The Gummy Bear Lab is a popular experiment in chemistry classrooms, designed to illustrate principles such as osmosis, diffusion, and chemical reactions. This lab typically involves immersing gummy bears in various solutions [...]

Since childhood, I have always been fascinated by the human body and the intricate mechanisms that govern its functioning. This fascination has been the driving force behind my ambition to pursue a career as a doctor. In this [...]

The Tuskegee Experiment, also known as the Tuskegee Study of Untreated Syphilis in the Negro Male, is considered one of the most notorious instances of unethical conduct in the history of medical research. The study, which began [...]

Addiction remains one of the most complex and pervasive issues facing modern society. The study of addiction, particularly through controlled experiments, offers valuable insights into the mechanisms behind addictive behaviors [...]

In A Class Divided experiment Jane Elliott chose to show her class a challenging exercise in the importance of segregation. She needed to demonstrate her understudies what segregation feels like, and what it can do to [...]

To observe the constituents and structure of metals and their alloys by means of an optical microscope. This is about to examine the microstructure of steel and observe the constituents and structure of it. Microstructure [...]

Related Topics

By clicking “Send”, you agree to our Terms of service and Privacy statement . We will occasionally send you account related emails.

Where do you want us to send this sample?

By clicking “Continue”, you agree to our terms of service and privacy policy.

Be careful. This essay is not unique

This essay was donated by a student and is likely to have been used and submitted before

Download this Sample

Free samples may contain mistakes and not unique parts

Sorry, we could not paraphrase this essay. Our professional writers can rewrite it and get you a unique paper.

Please check your inbox.

We can write you a custom essay that will follow your exact instructions and meet the deadlines. Let's fix your grades together!

Get Your Personalized Essay in 3 Hours or Less!

We use cookies to personalyze your web-site experience. By continuing we’ll assume you board with our cookie policy .

• Instructions Followed To The Letter
• Deadlines Met At Every Stage
• Unique And Plagiarism Free