Diffusion and osmosis lab
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Diffusion and osmosis lab. Outline of the day. Turn in your lab reports at the front More than 10 minutes late = bad Any questions on last week’s lab? Quiz Introduction to the lab Lab! Check out Get a stamp Make sure I mark you down for attendance. Quiz.

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Outline of the day
Outline of the day

  • Turn in your lab reports at the front

    • More than 10 minutes late = bad

  • Any questions on last week’s lab?

  • Quiz

  • Introduction to the lab

  • Lab!

  • Check out

    • Get a stamp

    • Make sure I mark you down for attendance


Diffusion and osmosis lab
Quiz

  • Ends 10 minutes after it’s started

    • Ends at: ____


Lab this week
Lab this week!

  • Exploring diffusion and osmosis

    • Effect of molecular weight on diffusion

      • Using agar plates!

    • Effect of temperature on rates of diffusion

      • Demonstration!

    • Using osmosis to determine solute concentration

      • Using dialysis tubing


Diffusion
Diffusion

  • “The movement of molecules or ions from areas of their higher concentration to areas of their lower concentration. Over time, the random movement of molecules will result in the even distribution of the material?”

    • Krogh, 2005

  • The “random movement of molecules or other particles, resulting in even distribution of the particles when no barriers are present”

    • Purves et al., 1995


Diffusion1
Diffusion

  • Start with a gradient of molecules

  • End with equal concentrations on both sides

Image pd by LadyofHats Mariana Ruiz Villarreal - http://en.wikipedia.org/wiki/Image:Simple_difussion_in_cell_membrane.svg


An animation of diffusion
An animation of diffusion

  • http://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.html


Molecular weight
Molecular weight

  • Sum of the mass of all atoms in the molecule

  • Three molecules

    • Silver Nitrate (AgNO3)

      • Mol. Weight: 170

    • Iodine potassium iodide (IKI)

      • Mol. Weight: 293

    • Methylene Blue

      • Mol. Weight: 373

      • C16H18N3ClS

AgNO3 image PD by Benjah-bmm27 from http://en.wikipedia.org/wiki/Image:Silver-nitrate-2D.svg; mb image PD by Calvero at http://en.wikipedia.org/wiki/Image:Methylene_blue.svg


Osmosis
Osmosis

  • Diffusion of water across a semi-permeable membrane

    • Water moves down its concentration gradient, just like any other molecule

No net movement of water in or out

Concentration

gradient:

100% water

Cell with pure water inside

100% water

These solutions are isotonic to each other

Pure water

(distilled water)

Image pd by LadyofHats Mariana Ruiz Villarreal - http://en.wikipedia.org/wiki/Image:Simple_difussion_in_cell_membrane.svg; other art by Marc Perkins


Osmosis1
Osmosis

  • Diffusion of water across a semi-permeable membrane

    • Water moves down its concentration gradient, just like any other molecule

Water moves into the cell by osmosis

Concentration

gradient:

90% water

Cell with 10% NaCl solution

100% water

The cell is hypertonic to the surrounding solution

Pure water

(distilled water)

Image pd by LadyofHats Mariana Ruiz Villarreal - http://en.wikipedia.org/wiki/Image:Simple_difussion_in_cell_membrane.svg; other art by Marc Perkins


Applying osmosis
Applying osmosis

  • We’ve got “urine” of an unknown concentration

  • You need to figure out what concentration it is, using osmosis

    • Dialysis tubing is a semi-permeable membrane

      • Water can cross it, but ions and large molecules cannot.

  • Methods note:

    • Wet the string before weighing the bag


Before you leave
Before you leave

  • Clean up your work area

    • Wash glassware and store upside down

  • Show me your lab report so I can stamp it

    • Need to have all data fields filled in

    • Complete at home and then turn in at the beginning of next lab

  • Remember that we’ll have a quiz at the beginning of the next class

    • 6-7 questions on today’s lab

    • 3-4 questions on the lab we’ll do next week


Notes for the instructor
Notes for the instructor:

  • Add any relevant cleanup instructions to the final slide (that slide is a generic one I’m adding to each presentation).


License information
License information

  • This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/us/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.

  • The slides in this presentation were originally created by Marc C. Perkins (http://faculty.orangecoastcollege.edu/mperkins).

  • You are free to use, modify, and distribute these slides according to the terms of the Creative Commons license (e.g., you must attribute the slides, no commercial uses are allowed, and future distributions must be licensed under a similar license).

  • Attribution should be given to Marc C. Perkins (and any later editors), including a link back to Marc’s current website. This applies both while distributing the slides and during use of the slides; attribution during use can be satisfied by, for instance, placing small text on at least one of the slides that has been shown (see below for an example).

Slides in this presentation based on those created by Marc C. Perkins. http://faculty.orangecoastcollege.edu/mperkins


History
History

  • August 2007: Marc Perkins released first version. http://faculty.orangecoastcollege.edu/mperkins

(If you modify these slides and redistribute them, add your information to the list)