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					                                Science Lesson Plan
                                      (70 minutes)

Student Name: Mike Tkachuk                   Grade: 8          Date:       April 2, 2007

      Activity:     Osmosis in Potatoes Experiment

        Strand:     Life Systems – Cells, Tissues, Organs, and Systems

Curriculum Expectations:
   By the end of Grade 8 students will:
     * demonstrate an understanding of the basic structure and function of plant and
       animal cells, and describe the hierarchical organization of cells in plants and
       animals;
     * investigate basic cellular processes and certain specialized cells in plants;
     * describe ways in which study of the structure, function, and interdependence of
       human organ systems can result in improvements in human health.


SpecificExpectations
Specific Expectations:

Understanding Basic Concepts
      * explain the function of selectively permeable membranes in cells

Developing Skills of Inquiry, Design and Communication
      * use appropriate vocabulary, including correct science and technology terminology,
        to communicate ideas, procedures, and results (e.g., use scientific terms such as
        organelle, diffusion, osmosis, selectively permeable)


Testing Materials:
Each group requires the following materials for the experiment:

 2 previously prepared raw potato slices of identical size
 2 identically sized beakers that can hold at least 250 mL
 graduated cylinder to measure water
 measuring spoon (tablespoon)
 sugar
 water
 2 labels
 2 elastics
 stirring rod
 saran wrap
 paper towel (second period only)
 balance (preferably electronic balance) capable of measuring in gram units
 Lab Write-up sheet
 Experiment Procedure sheet
Introductory Activity: (5 minutes)

Review the concepts from last day. Have students open their books to Page 28.

For 8W remind them of the small exercises they performed last day involving a high
concentration of students on one side of the room and the “movement of the students
from an area of high concentration to an area of lower concentration”. We said diffusion is
the movement of molecules from an area of high concentration to an area of lower
concentration.” The students diffused in our exercise.

We then had three different students (representing molecules) go outside the door and I
treated the three of them differently before letting them back in.
When they each knocked on the door, I acted like a cell membrane and:
a) let one in immediately (permitted passage)
b) did not let one in (did not permit passage)
c) selectively decided to let one in (selective passage)

When I permitted passage I acted like a cell membrane that that was permeable.
Permeable means permitting passage.

When I didn’t permit passage I acted like a cell membrane that that was impermeable.
Permeable means permitting passage.

When I selectively decided to let a student in, I acted like a cell membrane that that was
selectively permeable.
Selectively permeable means permitting some substances to enter or leave, but not others.

I also introduced the concept of osmosis refers to the diffusion of water through a
selectively permeable membrane from an area of high concentration to an area of lower
concentration. Osmosis is a special case of diffusion.

For 8S, remind them of the experiment they did where they had three types of coverings
on their beakers. They probably found that:

a) the saran wrap (or glass) didn’t permit passage of any substances and was therefore
impermeable.
Impermeable means not permitting passage.

b) the wire mesh permitted passage of all substances and was therefore permeable.
Permeable means permitting passage.

c) the cloth (or coffee filter) permitted passage of some substances but not others and
was therefore selectively permeable.
Selectively permeable means permitting passage to some substances but not others.

As per the teacher’s resource guide, introduce the concept of osmosis as a special case of
diffusion. Osmosis is the diffusion of water through a selectively permeable membrane
from an area of high concentration to an area of lower concentration.
Introduce the concept of solute and solvent.

Have a student read the top paragraph of page 31.

Put up the graphic chart on the board and go over it together. Tell the students that in
the experiment they will eventually perform, a solute will be dissolved in a solvent to form
a solution.

Solute – a substance that is dissolved in another substance, the solvent to form a solution
ie) sugar dissolved in water

Solvent – the substance that dissolves a solute to form a solution ie) water
Experiment Procedure Sheet: (10 minutes)

Review all experimental procedures and check over all required equipment before starting
the experiment. Do not begin until everyone understands what is required to be done and
how.

PROCEDURE:

   1. Attach the “WATER” label to one beaker and the “SUGAR” label to the other
      beaker with the elastics provided.

   2. Use your graduated cylinder to get enough water to place exactly 100 mL of water
      into each beaker.

   3. Place 3 LEVEL tablespoons of sugar in the beaker marked “SUGAR” and stir with
      the stirring rod until the sugar is dissolved.

   4. Using your balance, weigh and record the mass of each potato slice for each type
      of water in the data chart at the bottom of this page as ACCURATELY AS
      POSSIBLE! (to the nearest gram)! Remember how you measured “mass” of an
      object from Math!

   5. Record the texture of your potato slices (hard or soft) for each type of water in
      the data chart at the bottom of this page BEFORE you place the potato slice in
      the water.

   6. Carefully cover both beakers with saran wrap and allow them to sit undisturbed
      overnight.

   7. On the next science period, carefully remove the sugar potato slice and blot it dry
      with a paper towel. Weigh and record the mass in the data chart. Observe any
      changes in the texture of this slice and record the observation in the data chart.

   8. Carefully remove the water potato slice and blot it dry with a paper towel. Weigh
      and record the mass in the data chart. Observe any changes in the texture of this
      slice and record the observation in the data chart.



                                       Texture                             Texture
                 Mass BEFORE                          Mass AFTER
Type of Water                         BEFORE                               AFTER
                  Insertion in                         Insertion in
 Potato Is In                        Insertion in                        Insertion in
                   Water (g)                            Water (g)
                                        Water                               Water
   WATER
   SUGAR
Lab Write-up (front page): (15 to 20 minutes)

Go over the first side of the Lab Write-Up sheet together covering the OBSERVE,
QUESTION, and PREDICT sections.

OBSERVE: Make detailed qualitative (information gathered in observations in which no
measurement takes place.) and quantitative (data obtained through measurement or
mathematical calculation) observations of your testing materials before beginning the
experiment.

Texture of potatoes?
Type of water : Tap (dirty or clean)?
Type of Sugar: white refined
Saran wrap to protect the contents of the beakers

100 mL of Water
Identical sizes of potato slices
Balance that can measure to the nearest gram
Graduated cylinder to accurately measure water in mL
Tablespoon to measure the sugar

QUESTION: What is the question we wish to answer by the end of the experiment?

How will water and sugar affect two different potato slices?



PREDICT: With your group formulate a detailed hypothesis about the outcome of the
experiment as well as an explanation for your prediction.

Potato in Water:
The potato sitting in water will gain mass.
Why? Cells in potatoes have selectively permeable membranes. Water will move from an
area of high concentration (water in the beaker) to an area of lower concentration (the
potato) through the process of osmosis.

Potato in Sugar Water:
The potato sitting in sugar water will lose mass.
Why? Cells in potatoes have selectively permeable membranes. Water will move from an
area of high concentration (the potato cells) to an area of lower concentration (the sugar
water.) through the process of osmosis. The concentration of water in the sugar water is
lower than the concentration of water in the potato cell.
Lab Write-up (back page): (25 to 30 minutes)

Students will now conduct the experiment. Go over the instructions under INVESTIGATE
before they begin.

ALSO make sure they fill in the appropriate boxes in the Data Chart on the Experiment
Procedure Sheet.

Allow 5 minutes for clean up.

TELL STUDENTS that the Lab Write–up and Data Chart are homework and will be
collected the next day!

Clean up the rest of the materials.




Assessment:

As per the Teacher’s Resource Guide Curriculum and Assessment map, assessment for
Section 1.8 can use part of the Understanding Concepts (Rubric 1) and Communication
(Rubric 2) rubrics for reading and answering questions and assessing the Lab Write-up
activity.



Reflection for Future Improvement:

				
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posted:11/1/2011
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