With institutions roughly the world shut dvery own, I recognize that you could be scrambling for tasks that can be done with students virtual. I have taken this timeless biology lab activity showing the values of diffusion and also osmosis and adjusted it as an online activity. I did this lab many kind of times via my 10th grade continuous bio class at Kelly High School in Chicearlier, but it can be supplied efficiently through kids varying from middle institution to AP Bio. Students deserve to check out with the background below and also make their very own graphs, analyze these data, and draw conclusions.

You are watching: How to determine the molarity of a potato

I recognize you are functioning harder than ever before to teach your students despite the obstacles you face. I hope you have the right to usage this task or one of the others on this blog. Instructions are here if you would like to develop free accessibility to y2kcenter.org for you students for 90-days. Stay well.

-Aaron Reedy


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Background

Molecules are constantly in activity as an outcome of a cell"s stored kinetic power, which reasons them to bump into each various other and relocate in random new directions. Diffusion is the movement of molecules from a room of wright here there are many (high concentration) to a space wbelow tright here are fewer (low concentration). Osmosis is the diffusion of water via a semipermeable membrane. It is vital to remember that a semipermeable membrane permits the solvent (generally water) to pass via, but restricts the activity of a solute (a point dissolved in the solvent). Water will move throughout a semipermeable membrane from an area of reduced solute concentration to an area of greater solute concentration.


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When each side of a membrane has actually equal solute concentration, the solution is shelp to be isotonic and also water molecules will be equally likely to move in both directions throughout the membrane. In the instance of a hypertonic solution, tbelow is more solute exterior the cell than inside the cell. Hypertonic services cause water molecules to move out of the cell and into the area of greater solute concentration. Conversely, in hypotonic solutions tright here is a greater solute concentration inside the cell than external, and water molecules move right into the cell. Whenever possible, water will constantly move from an area of high water concentration/low solute concentration to an area of low water concentration/high solute concentration.


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In this activity, we are going to check out osmosis by looking at a datacollection created via a timeless classroom experiment. The experiment uses pieces of potato that are put in six different services of water each via a different solute concentration. The solute is sucincreased and also the concentrations are measured in devices of molarity. The services variety from no solute to a high concentration of solute and are 0.0 (distilled water), 0.2, 0.4, 0.6, 0.8 and also 1.0 molar succlimbed.

Pieces of potato are cut to equivalent sizes, weighed, and then put in among the six remedies overnight. The next day, the potato pieces are rerelocated from the solutions, blotted dry, and their last masses are recorded.

Each row in this tidy dataset contains an monitoring for a single potato item. Each column in the dataset is a variable and the cells in that column are the worths of that variable. The variables taped for each potato piece are Lab Group Name, Sucrose Concentration (Molarity), Initial Mass (g), Final Mass (g), and Mass Change (%).


To view a video clip clearly illustrating and also explaining the basic procedure for this lab, watch Paul Andersen’s Bozeman Science video walkthrough:


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The activity

1. Click the yellow Make a graph switch to visualize your information. Choose the scatter plot symbol and Sexactly how Sucincreased Concentration (Molar) on the X-axis and Mass Change (%) on the Y-axis. You have the right to add descriptive statistics choose means and medians by checking the box simply to the best of the graph.

Observe patterns in the data:

2. What are the independent and also dependent variables in this experiment?

3. How does Change in Mass (%) adjust with Sucrose Concentration (Molarity)?

4. Which substance moved throughout the cellular membrane in this activity? What is the certain name of the movement in regards to this substance?


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5. Now, change the variable referred to as Succlimbed Concentration (Molarity) to a Numeric variable with the dropdown menu ideal listed below the variable name near the peak of the web page. Then add it back to the graph aacquire by clicking the Sexactly how button. Finally, include a regression line of ideal fit by checking the box just to the best of the graph.

What is your finest estimate for the herbal solute concentration inside a potato cell? Explain just how your information is evidence for that estimate.

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6. Which solution is closest to being isotonic with respect to a potato cell? Which services were hypertonic/hypotonic? How perform you know?

Challenge question:

7. Using the ethics depicted through these data, describe why you can’t drink seawater once shed at sea.


For a quick explanation of diffusion and also osmosis, we very recommfinish Paul Andersen’s AP Biology Lab 1: Diffusion and Osmosis video. The explanation of the potato lab starts at 5:36.