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Example of a Good Lab Report Introduction Osmosis is by va23823

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									Example of a Good Lab Report

         Osmosis is a specialized case of diffusion that involves the passive transport of water. In osmosis,
water moves through a selectively permeable membrane from a region of its higher concentration to a
region of its lower concentration. The membrane selectively allows passage of certain types of molecules
while restricting the movement of others.
         The solute concentration in the beaker is higher than that placed in the dialysis bag, and thus the
water concentration is lower in the beaker than in the bag. This causes water to move from the bag into the
beaker. This can be observed by adding a dye to the solution within the dialysis bag.

         The first step of this experiment is to fill an empty beaker with a 0.8M solution given by the
instructor, followed by preparing a dialysis semi-permeable bag in which to measure osmosis. To prepare
the bag, one must first gently loosen the two semi-permeable walls from one another to open what now
looks like a flimsy tube. Gently, tie off one end of the tube tightly with the yarn. Next, fill the bag with a
0.2M solution given by the instructor and add one drop of green food coloring. Finally, tie off the open end
of the bag as tightly as possible.
         Once the beaker and bag has been prepared, the next step is to weigh and record the initial weight
of the semi-permeable bag. After completing this step, one is to place the prepared bag into the prepared
beaker and wait for about eight minutes.
         After allowing the bag to sit inside the solution within the beaker, the bag is removed from the
beaker and weighed again. Finally, this new weight is subtracted from the initial weight to show how much
water the dialysis bag lost due to osmosis. Finally, to further prove osmosis occurred, one is to look at the
remaining solution in the beaker. If there is a hint of green, then one can conclude that osmosis took place.

Results and Conclusion
          The results of this lab mirrored what was to be expected. There are often several different types of
molecules in a solution. The motion of each type of molecule is random and independent of other
molecules in the solution. Each molecule moves down its own concentration gradient, from a region of its
high concentration to a region of its low concentration.
          Though the net movement of molecules is down their concentration gradient, at any time
molecules can move in both directions as long as the membrane is permeable to the molecule. Keep this in
mind while you take a closer look at the beaker below. Some human errors that could have occurred would
be mostly focused around opening and properly closing the dialysis bag. Some participants had issues in
gently opening the bag, which resulted in a tear in the bag leading to a leaking of the 0.2M solution. Others
did not tie of the bag securely enough which caused a greater outflow of the solution and therefore a greater
loss of water.


    1.   Will there be a net movement of water between two isotonic solutions?

         An isotonic solution occurs when there is an equal concentration of particles on each side of a
semipermeable membrane. In order for particles to move, there needs to be a concentration gradient. A
gradient occurs when there are unequal concentrations of particles on either side of a semipermeable
membrane. Because there is no difference in concentration between two isotonic solutions, there will be no
net movement of water between them.

    2.   Why don't red blood cells pop in the bloodstream?

        In order for cell to expand due to osmotic forces, it needs to be placed in a hypotonic solution. A
hypotonic solution has a relatively low concentration of dissolved particles, when compared to the amount
of dissolved particles on the inside of a cell. The liquid portion of the blood is considered to be isotonic to
red blood cells. For this reason, there is no net movement of water inside or out of the cell, causing the cell
to remain a constant size.
                                                                            Name: ________________

                 Yes (4 pts.)           Yes, but (3 pts.) No, but (2 pts.)           No (1 pt.)
Accuracy         The lab report         The lab report         The lab report did    The lab report
                 contained logical      contained logical      not contain any       showed no attempt
                 scientific thought.    scientific thought,    scientific thought,   at          scientific
                 Each component         but some of the        but had       some    thought           and
                 contained accurate     sections contained     accurate              contained       many
                 information.           inaccurate             information.          instances           of
                                        information.                                 inaccurate
Format           All             four                          One component is      More than one
                 components       are                          missing from the      component           is
                 clearly visible in                            lab report.           missing from the
                 the lab report.                                                     lab report.
Creativity       The lab report         The lab report         The lab report        The lab report did
                 contained creative     contained       some   included very few     not include any
                 ideas that made the    creative ideas, but    creative ideas.       unique or creative
                 reader think about     very little forward                          ideas.
                 possible next steps.   thinking         was
Writing Skills   There are less than    There are 5-10         There are 5-15        There are more
                 5          spelling,   spelling, grammar,     spelling, grammar,    than 15 spelling,
                 grammar, and/or        and/or punctuation     and/or punctuation    grammar, and/or
                 punctuation errors     errors present in      errors present in     punctuation errors
                 present in the lab     the lab report.        the lab report.       present in the lab
                 report.                                                             report.
Timeliness       The lab report was                                                  The lab report was
                 turned in on time                                                   turned in late.
                 to Criterion.     A
                 hard copy was also
                 submitted in class.

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