Gummi osmosis experiment
Important note: This activity takes at least 2 days in a row to complete. You must start it at least 48 hours before the assignment is due. It is worth 30 points.
Do not attempt this activity until after you have completed the lessons on transport across cell membranes and a closer look at osmosis (Lessons 4C and 4D). They provide the necessary background.
Also, please note that you will not receive any credit on this assignment if you do not submit all of the required photos as documentation of your completion of the activity. You will be prompted when it is time to take your first photo.
Learning outcomes
• Using a hands-on approach, demonstrate osmosis in an object containing a semi-permeable membrane — in this case, a Gummi bear.
• In a given situation, be able to identify the hypotonic solution and the hypertonic solution, and based on how osmosis works, predict which direction the water will flow.
Activity time line
• First, turn in your initial hypotheses, data, and picture; start the soak in your refrigerator (i.e. “initial”).
• At least 24 hours later, turn in your first set of results and pictures (i.e. “24 hours”).
• At least 24 hours after that, turn in your second set of results and picture (i.e. “24 hour switch”).
Required materials
Figure A4-1: The required materials include Gummi bears.
You will need the following:
• Gummi bears (you only need three of them, but they must be three different colors)
• A way to keep the Gummi bears cold during the course of the entire experiment (e.g. a refrigerator)
• A metric ruler with millimeter (mm) increments
• Two medium sized plastic or glass containers that can hold at least a cup of liquid each
• Access to tap water (do not used distilled water)
• Choice of one of the following to serve as a test solution: imitation maple syrup, corn syrup, Karo syrup, agave nectar, sugar solution (1 cup of table sugar in 1 cup water), or salt solution (one quarter cup salt to one and a quarter cups water)
• Paper towels (a few)
• Digital camera for taking photos, and a way to transfer those photos to your computer for uploading with your assignment
• A picture identification card (e.g. Pima school ID or driver’s license) to include in your photo documentation
• A pen, paper, and pair of scissors for creating labels for your photos
Introduction
Recall from your lessons that osmosis is defined as the passive movement of water across a semi-permeable membrane (e.g. a cell membrane) from an area of high “free” water concentration to an area of low “free” water concentration. The water moves as a result of the differences in solute concentrations of the solutions on either side of the semi-permeable membrane. Thus, the water will always move from the hypotonic solution, across the semi-permeable membrane, to the hypertonic solution.
Osmosis can occur in anything with a semi-permeable membrane that prevents movement of the solutes, while at the same time allowing movement of the water. The gelatin that helps a Gummi bear keep its shape creates a perfect model for demonstrating osmosis. A Gummi bear will behave in a very similar way to a cell when it comes to osmosis.
The following YouTube video is a great review of osmosis. Note the reference to the Gummi bear, which you will use in this activity. Be sure that you have your audio turned on. Don’t be surprised if you have the song stuck in your head for a while! Closed captioning is available.
YouTube video: A review of osmosis with an emphasis on the Gummi bear.
Setting up your Gummi osmosis experiment
Step 1: Choose your Gummi bears, and measure them.
You will be using three pieces of candy. One piece will be a control that won’t be placed into a solution. The other two pieces will be experimental treatments that will be placed into solutions of differing solute concentrations. Be sure to choose three different colors of Gummi bears, so that it is easy to keep track of which is your control, and which has been placed into each solution.
Figure A4-2: Use a metric ruler to measure each dimension of the Gummi bear. The height of this Gummi bear (measured along its central axis) is 14 mm.
Measure the three different dimensions of each of your Gummi bears (i.e. height, width, and depth) and record each of these numbers in a computer document. Be sure that your document file name has the word “initial” in it to differentiate it from the two other documents that you will create later on. Also, be sure to include your units (mm) with each number. Your measurements must be in millimeters (mm). You may either create a table or a list. Just make sure that your data can be clearly read. Next, multiply the height, width, and depth measurements of each Gummi bear in order to determine their volumes. This will give us a single number for each to use as comparison later on. You will be turning in this information with your “initial” document submission.
For example, if your Gummi bear has a height of 14 mm, a width of 6 mm, and a depth of 6 mm, you would multiply 14 x 6 x 6. This gives you a volume of 504 mm3 for that Gummi bear.Determine the volumes of each of your Gummi bears and record them in your “initial” computer document. These are your “initial” volumes.
Step 2: Decide on your two different test solutions.
One of your test solutions must be tap water. Do not use distilled water for this experiment. The other solution needs to be a saturated sugar or saturated salt solution. This means that it needs to be very concentrated. I recommend using what you already have at home, if possible, so that you don’t need to buy anything. You will need at least a cup of this solution. Here are some suggestions (choose only one solution):
• Imitation maple syrup, corn syrup, Karo syrup, or agave nectar
• Solution of table sugar and water; slowly add 1 cup of table sugar to 1 cup boiling water; stir until all sugar is dissolved and allow to cool completely before using (I recommend chilling it in your refrigerator)
• Solution of salt and water; slowly add one quarter cup salt to one and a quarter cups boiling water; stir until all salt is dissolved and allow to cool completely before using (I recommend chilling it in your refrigerator); it is ok if some of the salt comes back out of solution
You will be putting your control Gummi bear in no test solution, your second Gummi bear in the saturated sugar or salt solution, and your third Gummi bear in tap water. However, don’t put them in the solutions yet! You need to first form some “initial” hypotheses, take a picture of your “initial” Gummi candy sizes, and submit your “initial” document in the Assignment 4 dropbox. Let’s first form some hypotheses.
Your initial hypotheses
Come up with a hypothesis for each of your three situations: control (no solution), sugar or salt solution (or syrup, agave nectar, etc.), and tap water. Consider what you know about osmosis and take your best, educated guess for each situation.
In your computer document, record your 3 different initial hypotheses. You will be submitting them with your “initial” document submission in the Assignment 4 dropbox.
Here is an example of a properly worded hypothesis for a pretend test solution: (start by saying, “I hypothesize that…”)
• I hypothesize that a Gummi bear placed in ambrosia will become smaller in size.
It is now time to take a digital photo to document your “initial” Gummi bear sizes. See example below. The photo must clearly show your three Gummi candies before they have been put into solutions, their corresponding labels (e.g. control, sugar, syrup, or salt solution, and water), a label that says “Initial: 0 hrs”, and a copy of your photo ID (e.g. Pima school ID or driver’s license) containing both your picture and your name. If you end up using your driver’s license, be sure to cover up your personal information, such as your driver’s license number, address, and signature. You don’t need to include yourself in this initial photo.
Figure A4-3: You need to obtain a picture showing your three labeled, “initial” Gummi bears, along with your photo ID, as documentation of your completion of this part of the activity.
Your initial document submission
It is now time to upload your “initial” computer document containing the initial measurements of each of your three Gummi candies (i.e. height, width, depth, and volume), your three initial hypotheses, and your initial picture showing the sizes of your Gummi candies along with your photo ID, into the Assignment 4 dropbox. I must receive this initial submission in the dropbox at least 24 hours before I receive your first set of experimental results, so send it right now! Otherwise, you will lose points.
Important note: you will not get any credit for this assignment if you do not upload your “initial” picture and computer document into the dropbox at least 24 hours before the assignment due date. Thus, you cannot begin this assignment on the last day of the deadline!
Feel free to include the documentation photo in your computer document, or you can send it as a separate file. If you upload it separately, please include the word “initial” in its file name. Your computer document must also include the word “initial.”
Beginning the experiment
Place your treatment Gummi bears into containers with their corresponding solutions. You need to use at least a cup of each solution (more is fine), and the Gummi candies should be completely covered by the liquid. Place the control Gummi bear in a sealed ziplock bag or sealed container. This is so that your refrigerator does not dry it out. Next, place all of your Gummi bears and containers in the refrigerator for at least 24 hours. It is important that you keep the Gummi candies cold while they are in solutions. They tend to dissolve at room temperature and we don’t want that to happen.
At the end of the 24 hour period
If it is more convenient to run the experiment a little longer than 24 hours, that is fine. What is important is that you run it for at least 24 hours.
After 24 hours have passed, take your Gummi bears and solutions out of the refrigerator. Remove the treatment Gummi candies from their solutions and blot dry with a paper towel. If you used a very thick, viscous solution you may want to first give your candy a quick rinse with water.
Again, measure the three different dimensions of each of your Gummi candies (i.e. height, width, and depth), and determine their volumes, but this time record the numbers in a brand new computer document, with “24hour” somewhere in its file name. Also, be sure to include your units (mm) with each number. Your measurements must be in millimeters (mm). You may either create a table or a list. Just make sure that your data can be clearly read. You will be turning in this information with your “24hour” document submission.
Next, copy your initial measurements and volumes from your “initial” computer document into this new, “24hour” document. Copy the initial data such that it is located either just above or just below the new data for the 24 hour measurements in your new document.
Compare the initial and final volumes for each Gummi bears and then answer the following questions in your new computer document, “24hour”.
1. Did the control change? If so, did its volume get bigger or smaller, and by how much? Would you expect the control to change?
2. Did the Gummi bear in sugar, syrup, or salt water change? If so, did its volume get bigger or smaller, and by how much?
3. Did the Gummi bear in water change? If so, did its volume get bigger or smaller, and by how much?
4. Based on your results, did you support or reject your hypothesis for the control? Explain.
5. Based on your results, did you support or reject your hypothesis for the Gummi bear in sugar, syrup, or salt water? Explain.
6. Based on your results, did you support or reject your hypothesis for the Gummi bear in water? Explain.
7. Did you prove any of your hypotheses? If so, which one(s)?
Note: You likely found that the Gummi bear in the sugar, syrup, or salt solution did not shrink in the way that you had predicted. If you had a scale you would have noticed a loss of weight. However, because the gelatin in the Gummi candy makes it resist shrinking, we don’t see a noticeable change in size, even though it lost a lot of water. That is why the next step in the procedure, the “24 hour switch”, is so important. We need to first stretch out the candy. After first making the Gummi candy grow in size in the water, we can now get it to shrink by puting it into the other solution (e.g. sugar, syrup, or salt).
It is now time to take digital photos to document your Gummi bear sizes after 24 hours. See examples below. One photo must clearly show your three Gummi candies after the 24 hour period, their corresponding labels (e.g. control, sugar, syrup, or salt solution, and water), a label that says “24 hrs”, and a copy of your photo ID (e.g. Pima school ID or driver’s license) containing both your picture and your name. If you end up using your driver’s license, be sure to cover up your personal information, such as your driver’s license number, address, and signature. You don’t need to include yourself in this first photo. The second photo must clearly show both your results after 24 hours and YOU. Be sure to get all of your Gummi candies, along with their labels, in the picture with you. Feel free to either take the picture yourself or have someone else take the photo.
Figure A4-4: You need to obtain a picture showing your three labeled, Gummi candies after the 24 hour period, along with your photo ID, as documentation of your completion of this part of the activity.
Figure A4-5: You need to also obtain a picture of yourself with your results (after 24 hours) as documentation of your completion of this part of the activity.
Your 24 hour document submission
It is now time to upload your “24hour” computer document containing the measurements of each of your three Gummi candies (i.e. height, width, depth, and volume) after 24 hours, your answers to the questions (#1-7), and your two required documentation photos (i.e. a photo of your 24 hour results with your ID and a photo of YOU with your results), into the Assignment 4 dropbox.
Feel free to include the documentation photos in your computer document, or you can send them as separate files. If you upload separately, please include “24hour” in their file names. Your computer document must also include “24hour”.
The 24 hour switch
If you started your osmosis experiment late, you will likely find that you don’t have enough time to do this last part. You need another 24 hours in order to complete it. This is why I asked you to start your osmosis experiment at least 48 hours (2 days) before the scheduled due date. If you have run out of time, skip to the end of the activity and answer the “End of the activity questions” (#11-15 only). However, note that you will receive a 5 point deduction for not completing the “24 Hour Switch” (this includes the point loss for questions #8-10). You don’t want to lose the points for the end of the activity questions, so be sure to complete them!
If you did plan your time well, and thus have another 24 hours to spare, then it is time to do a switch. You will now switch solutions for your two treatment Gummi bears. Put the Gummi candy that was originally in the water into the sugar, syrup, or salt solution. Likewise, put the Gummi candy that was originally in the sugar, syrup, or salt solution into the water. Put the Gummi candies and solutions back into the refrigerator for another 24 hours.
After at least 24 hours have passed, remove them from their solutions, blot them with paper towels, and prepare them for one last picture. You don’t need to take any measurements this time.
It is now time to take a digital photo to document your “24 hour switch” Gummi bear sizes. See example below. The photo must clearly show your three Gummi candies after the switch has occurred, their corresponding labels (e.g. control, sugar, syrup, or salt solution, and water — be sure the label matches what you put the Gummi bear in for the switch), a label that says “24 hrs (switch)”, and a copy of your photo ID (e.g. Pima school ID or driver’s license) containing both your picture and your name. If you end up using your driver’s license, be sure to cover up your personal information, such as your driver’s license number, address, and signature. You don’t need to include yourself in this photo.
Figure A4-6: You need to obtain a picture showing your three labeled, “24 hour switch” Gummi bears, along with your photo ID, as documentation of your completion of this part of the activity.
End of the activity questions
Answer the following questions in a new computer document. Give it a different name than your previous two computer documents. Feel free to include the documentation photo of your 24 hour switch (if you did it) in your computer document, or you can upload it as a separate file. If you send the photo separately, please include “switch” in its file name.
Note: You can only receive credit for questions #8-10 if you ran the switch for the full 24 hours and turned in a proper picture of your 24 hour switch results. If you did not do this part, then skip questions #8-10.
8. Compare your 24 hour and 24 hour switch pictures for your Gummi candy that was originally in the water, but then switched to the sugar, syrup, or salt solution. What differences do you observe?
9. Compare your 24 hour and 24 hour switch pictures for your Gummi candy that was originally in the sugar, syrup, or salt solution, but then switched to the water. What differences do you observe?
10. Based on your results of the switch, does it appear as though osmosis is reversible?
Regardless of whether or not you completed the 24 hour switch, be sure to answer all of the following questions.
11. Based on your experimental results, was one of your solutions clearly hypertonic to your Gummi candy? If so, which solution was the hypertonic solution? (hint: this question is best answered by looking at both your 24 hour and 24 hour switch results; the gelatin in Gummi candies makes them very resistant to changes in shape, even when put into a hypertonic solution; however, the 24 hour switch helps to clarify your results)
12. Based on your experimental results, was one of your solutions clearly hypotonic to your Gummi candy? If so, which solution was the hypotonic solution?
13. Suppose a human blood cell containing a 0.9 percent solute concentration were put into a container of 0 percent solute solution (i.e. distilled water). Would the blood cell get bigger or smaller? Why? In your explanation, you must tell me which area has the hypotonic solution (inside the blood cell or outside the blood cell), which area has the hypertonic solution (inside the blood cell or outside the blood cell), and which direction the water would be moving (into the cell or out of the cell).
14. Suppose a human blood cell containing a 0.9 percent solute concentration were put into a container of 30 percent solute solution. Would the blood cell get bigger or smaller? Why? In your explanation, you must tell me which area has the hypotonic solution (inside the blood cell or outside the blood cell), which area has the hypertonic solution (inside the blood cell or outside the blood cell), and which direction the water would be moving (into the cell or out of the cell).
15. What percent solute concentration would be isotonic to this blood cell?
Your evaluation of the activity
1. Did the activity help you to understand the concept of osmosis?
2. Are the directions for the activity clear?
3. What part of the activity was confusing?
4. Include any suggestions you have to improve this activity.
Thanks for your input.
End of the activity document submission
It is now time to upload your last computer document containing the end of the activity questions (#8-15) and your documentation photo of your 24 hour switch (if you did it) into the Assignment 4 dropbox.
Feel free to include the documentation photo in your computer document, or you can send it as a separate file. If you upload it separately, please include “switch” in its file name.
Congratulations! You are now done with this activity!
You will not receive any credit for this assignment if you do not submit all of the required photos (minimum: “initial” picture with ID, “24 hour” picture with ID, and picture of yourself with 24 hour results). If you are not able to complete and take a photo of the last part (“24 hour switch”), your assignment will still be accepted, but with a loss of 5 points for not doing the switch.
Grading criteria

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