Osmosis and Diffusion Lab using Potato Cores
Instructions and Rubric
Introduction: Water can move through protein channels in cell membrane/cell walls. The water
will move due to the water potential of the cells. If there is a greater concentration of solutes
(chemicals) inside the cell than outside the cell and the chemicals can not move, then water will
respond by moving into the cell. This process involves water gradients called water potentials. If
one area has a great deal of water, it has a high water potential. If an area has a great deal of
dissolved material (less water) it has a low water potential. Water will attempt to move down it
gradient, that is, from high to low water potential. You job is to observe this using potato cores that
are placed into various solutions of sugar water. The sugar is too big to easily move through the
cell membrane/cell wall. So, depending on the water potential of the cells vs the solution water
will move in or out. This lab lets you observe this and determine the concentration of solutes in the
potato cells.
Materials:
 You will be working in groups of 4 if at all possible to share the work load (2 buddy groups)
 Potato cores (4 per condition)
 Sucrose solutions (.2, .4, .6, .8, 1.0 )
 Distilled water
 Electronic balance
 Plastic weighing tray
 Plastic cups (6)
 Graduated cylinder (50 ml)
 Scalpel
 Marking tape
 Blue tweezers
Procedures
 Using marking tape, label 6 cups with the following solution types (.2, .4, .6, .8, 1.0 and Di
water)
 Place approximately 50 ml of the various solutions, each cup receiving a separate solution.
Suggestion, measure the di water with the graduated cylinder, and fill the other cups to the
same level
 Obtain 24 potato cores and cut them to equal sizes (about 2.5 cm). All the cores you use
must be the same length
 Divide your 24 cores into 6 groups and gently blot them dry with a paper towel
 Using the electronic balance and plastic weighing tray mass (weigh) each group of potato
cores and record the data in a table that is labeled with a detailed title and which provides
the error measurement of the electronic scale. MAKE SURE TO TARE THE TRAY. The table
should record the type of solution in the cup and the mass of the potatoes in the cup.
 Place the potato core sets in their appropriate cup and place in Mr. Boyer’s back prep room
in the fume hood that is labeled with your block (3B or 4B).
 PS make sure to indicate on your cup your group number, Mr Boyer will assign group
numbers during the lab
 24 hours later (app) you will need to come and measure the mass of your potato cores. To
do this you must pore off the fluid in the cup and use the plastic blue tweezers remove the
cores, blot them dry just as you did in the set up phase and final measure them using a
plastic weighing tray. MAKE SURE TO TARE THE TRAY. Record your potato group mass on
your data chart.
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Finally dump your potato cores in the trash and wash and dry your equipment (cups,
tweezers and return them to their stations
Calculations. For each setup (all 6) you will need to calculate a percent mass change. To do
this you will use the following formula (final mass-initial mass)/initial mass x 100. You will
need to record this data in your data table as well. Make sure to keep track of the positive
and negative changes if they occur
Report
You will create a report for this Lab: The parts should be as follows:
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Title
Research Question ( for example “will there be a difference in the movement of water in or
out of a set of potato cores if they are placed in solutions with different concentrations of
sucrose”
Introduction that explains a bit about the process that is used to move water across a
membrane and why water moves (Background information.. use your text, class notes, and
lab intro…)
Hypothesis: Develop a clear prediction about what you think will occur (Have it checked by
Mr. Boyer. It is best to do this before you begin. You will place your groups hypothesis on a
note card and give it to Mr. Boyer. Your hypothesis should be in an if… then statement
where the independent variable, the “if” and the “then”, the dependent variable can easily be
noted
Variable identified: You have identified the Independent, Dependent, and Control variable
present in the experiement
Materials you can copy the list above
Procedures. You can copy the list above, but you must also must photo document each step
using your computers. Take the procedures and take a pic at each step.
Data Chart (Title, error measurement, clearly and easily understood, with percent error
calculation)
Graph of the Results. You must graph the data placing the sucrose concentrations along
the x axis and the mass change along the y axis. You can hand draw the graph or use excel,
but the graph must have a title, labeled axis and a best fit line. Mr. Boyer will describe how
to do this (excel can do it automatically, hand drawn graphs use a ruler to find the best line).
The graph should be full page size for ease of reading.
Conclusions: You will evaluate your results by describing the changes in mass you
observed. You will make observations about what the various sucrose concentration did to
the mass of the potato. You will report the point where the best fit line crosses or touches
the x axis. This point indicates the water potential of the potato cores (the solute
concentration inside the cores). You should compare your water potential number with
other groups in class (Mr. Boyer will facilitate) to see if your number is similar to others. If
it was very different, you should speculate about the difference……
Evaluation/Reflection: What went right, What went wrong, What did you learn, How
could you do the lab better.
Will be starting this on Oct 14, The lab report will be due on Oct 25 to drop box. You should also
add it to your wiki using the wiki format. In the wiki, you can place the entire file in an upload. You
should, however, add a title to the wiki page, a brief description of the project, the file, and you can
cut and paste your Evaluation/Reflections from your file to the wiki page. Place at least 2 images
from your file to the wiki page to assist the viewer better understand the lab
• Lab Report : Diffusion and Osmosis in Potato Cores
Grading Rubric
• Teacher Name: T Boyer
• Student Name: ________________________________________
•
CATEGORY
4
3
Appearance/Org Lab report is typed
Lab report is neatly
anization x2
and uses headings
handwritten and uses
and subheadings to
headings and
Images that
visually organize the subheadings to visually
outline the
material. Title is
organize the material.
procedure are
clearly visible and
Title is present but is not
included
informative
informative
appropriately
Images present to
Images present but do
support
not adequately support
Research
The purpose of the
The purpose of the lab
Question and
lab or the question to or the question to be
Introduction x2
be answered during
answered during the lab
the lab is clearly
is identified, but is stated
identified and stated. in a somewhat unclear
manner.
Introduction included
and is detailed and
Introduction included
complete
and is somewhat
detailed
Experimental
Hypothesis
Variables
(IV,DV,CV’s)
Materials
Procedures
Data
Conclusion x2
2
Lab report is neatly
written or typed, but
formatting does not
help visually
organize the
material. Title is
vague or misleading
1
Lab report is
handwritten and
looks sloppy with
cross-outs, multiple
erasures and/or
tears and creases.
Title is not present
Few images present
The purpose of the
lab or the question
to be answered
during the lab is
partially identified,
and is stated in a
somewhat unclear
manner.
Introduction is
included but is not
detailed
Hypothesized
Hypothesized
Hypothesized
relationship between
relationship between the relationship between
the variables and the
variables and the
the variables and the
predicted results is
predicted results is
predicted results has
clear and reasonable
reasonable based on
been stated, but
based on what has
general knowledge and
appears to be based
been studied.
observations.
on flawed logic.
All variables are
All variables are clearly Most variables are
clearly described with described with most
clearly described
all relevant details.
relevant details.
with most relevant
details.
All materials and
Almost all materials and Most of the
setup used in the
the setup used in the
materials and the
experiment are
experiment are clearly
setup used in the
clearly and accurately and accurately
experiment are
described.
described.
accurately
described.
Procedures are listed Procedures are listed in a Procedures are listed
in clear steps. Each
logical order, but steps
but are not in a
step is numbered and are not numbered and/or logical order or are
is a complete
are not in complete
difficult to follow.
sentence.
sentences.
Professional looking
Accurate representation
Accurate
and accurate
of the data in tables
representation of the
representation of the
and/or graphs. Graphs
data in written form,
data in tables and/or
and tables are labeled
but no graphs or
graphs. Graphs and
and titled.
tables are presented.
tables are labeled and
titled.
Conclusion includes
Conclusion includes
Conclusion includes
Images not present
The purpose of the
lab or the question
to be answered
during the lab is
erroneous or
irrelevant.
Introduction not
included
No hypothesis has
been stated.
Variables are not
described OR the
majority lack
sufficient detail.
Many materials are
described
inaccurately OR are
not described at all.
Procedures do not
accurately list the
steps of the
experiment.
Data are not shown
OR are inaccurate.
No conclusion was
Wiki Upload
Lab Skills
whether the findings
supported the
hypothesis, possible
sources of error, and
what was learned
from the experiment.
Report has properly
been added to your
wiki in a clear and
concise manner
whether the findings
supported the hypothesis
and what was learned
from the experiment.
what was learned
included in the
from the experiment. report OR shows
little effort and
reflection.
Report has been added
to your wiki but there
are formatting issues or
it is missing important
parts
Lab is carried out
with full attention to
relevant safety
procedures. The setup, experiment, and
tear-down posed no
safety threat to any
individual.
Lab is generally carried
out with attention to
relevant safety
procedures. The set-up,
experiment, and teardown posed no safety
threat to any individual,
but one safety procedure
needs to be reviewed.
Report has been
added but is in a
format that is
difficult to
understand or it is
missing important
parts
Lab is carried out
with some attention
to relevant safety
procedures. The setup, experiment, and
tear-down posed no
safety threat to any
individual, but
several safety
procedures need to
be reviewed.
Date Created: Oct 13, 2010 07:31 pm (CDT)
Total pts____________
Report has not been
added to the wiki,
but you have
completed it and
shown a paper copy
to Mr. Boyer
Safety procedures
were ignored
and/or some aspect
of the experiment
posed a threat to
the safety of the
student or others.