Pre-Activity Checklist
- Make sure you know how your computer/device saves screenshots
Follow this link to get details on how to take and save a screenshot - Read the background material to help you understand the concepts related to this activity
- Get the Activity Form and Additional Data (look under the Activity Form tab)
- Record your Activity Data Code in your Activity Form
- Close any unneeded browser tabs for best performance
Important: Please note that your instructor may have specific guidelines regarding screenshots. For example, your instructor may require additional screenshots or may prefer that screenshots are submitted in a particular manner. Please ask your instructor what their expectations are to ensure that you are meeting their requirements.
Activity Procedure
In this activity you will study osmosis. You will take data for three different test solutions as detailed below in Procedures I, II, and III. In Procedure I the same solution (water) is used on both sides of the semipermeable membrane. In Procedures II and III you will observe the effects of osmotic pressure due to concentration differences on opposite sides of the semipermeable membrane. Experimental data will allow you to determine the concentration of test solution 3 (see the Summary of Formulas Needed for Calculations in Background tab).
Procedure I ‐ Test Solution 1: Water
In this procedure you will explore osmosis when both solutions are identical (water).
Pick two different starting water volume settings between 1.50 L and 2.28 L for your trial 1 and trial 2 data runs. Record these values in Data Table I of your Activity Form.
- select Solution 1 by clicking or tapping on its button
- adjust the starting water volume to the desired trial value using the slider
- click the Start Data Run button ‐ monitor volume changes on both sides of the membrane
Note: allow 30 seconds for the data run to complete ‐ do not interrupt the data run - record final volume data in Data Table I
- take a screenshot of this completed data run (it will be used to confirm your identity and Activity Data Code)
- press the reset button and run your second trial (repeat steps 1-4) or move on to the next procedure
Procedure II ‐ Test Solution 2: Guanine solution (known concentration)
In this procedure you will explore osmosis when different solutions are separated by a semipermeable membrane.
Pick two different starting water volume settings for your trial 1 and trial 2 data runs. Record these values in Data Table II of your Activity Form.
- select Solution 2 by clicking or tapping on its button
- adjust the starting water volume to the desired trial value using the slider
- click the Start Data Run button ‐ monitor volume changes on both sides of the membrane
Note: allow 30 seconds for the data run to complete ‐ do not interrupt the data run - record final volume data in Data Table II
- press the reset button and run your second trial (repeat steps 1-4) or move on to the next procedure
Procedure III ‐ Test Solution 3: Cytochrome C solution (unknown concentration)
In this procedure you will again explore osmosis when different solutions are separated by a semipermeable membrane. Your data will allow you to determine the concentration of this test solution. Note: the concentration of this test solution is an unknown value and will likely be different for each user.
Pick two different starting water volume settings for your trial 1 and trial 2 data runs. Record these values in Data Table III of your Activity Form.
- select Solution 3 by clicking or tapping on its button
- adjust the starting water volume to the desired trial value using the slider
- click the Start Data Run button ‐ monitor volume changes on both sides of the membrane
Note: allow 30 seconds for the data run to complete ‐ do not interrupt the data run - record final volume data in Data Table III
- press the reset button and run your second trial (repeat steps 1-4) or move on to the post-activity work below
Post-Activity
Complete the Tables on your Activity Form. To help with the questions & calculations, please review the background material (see the Summary of Formulas Needed for Calculations in Background tab) and your data.