L.3 Osmosis in a Potato
The lab performance should be used to complete all lab reports (in 12-14pt. font).
Delete all of the instructions in blue & use all of the writing in black as your section headings.
NAME:
Date:
Title: Write an investigative question for this experiment.
Hypothesis: Write a hypothesis. Your hypothesis should have a clear and specific prediction
with a valid scientific reason.
Variable Table: Complete table below.
Independent variable
Dependent variable
Control Variables
1
2
3
Equipment
• Potato
• Standard Sugar Solution ( 1 M Sugar, 0.5 M, 0.25 M, 0.125M and O M (distilled Water))
• Wash Bottle
• Ruler
• Test Tubes and Test Tube Rack
• Cork Borer
• Scalpel
• Cutting Board
• Scales accurate to 2.d.p
• 10ml Syringe
• Paper towels
Method
1.
2.
3.
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8.
9.
Firstly, the cork borer needs to be used to cut out a piece of potato at least 4 cm in length. This allows room for trimming
off untidy edges.
On the cutting board the cylindrical piece of potato needs to be cut to 35mm. Using a ruler, measure this as accurately as
possible and cut the potato to 35mm in length using a scalpel. ( be sure to record the uncertainty of measurement)
Using the scaled weigh the potato and record the mass in grams. ( be sure to record the uncertainty of measurement)
The test tube rack and test tubes need to be assembles. Fill a syringe with exactly 10ml or sugar solution (strength 1M)
and empty into a test tube.
Now the timing device needs to be reset and readied. An extra pair of hands to aid in the timing may be useful. This
potato piece can now be placed into the test tube containing 10mL of 1M sugar solution.
As the potato piece is placed in the test tube, the timer should be started. After 30 minutes the potato piece needs to be
removed from the test tube.
Dry potato on a paper towel. Then measure its mass and length.
Record data in data table
Repeat this experiment for 0.5 M, 0.25 M, 0.125M and O M (distilled Water) concentration solutions of sugar solution.
Initial Raw class data
Group 1
Group 2
Group 3
Group 4
Group 5
Final Raw Data table length and mass after 30 minutes
Group 1 Data
Group 2
Group 3
Group 4
Group 5
Process Data:
Raw Data (DCP Aspect 1)
Table : Include a descriptive table title that summarizes the investigation including the
independent & dependent variables
a. Include a descriptive table title that summarizes the investigation including the
independent & dependent variables [& if appropriate, essential control variables
b. Label column & row headings.
c. List the units with column & row headings (units should not be included with the raw data).
d. Estimated the uncertainties: uncertainty is estimated as the smallest division that the
instrument can read. In this case 0.1 mg/ mL .
e. All uncertainties are stated as absolute values (not percent) to one significant digit.
f. Data is recorded with the same precision as the uncertainty (i.e. with the same number of
decimal places as the uncertainty).
* All uncertainties must be rounded to one significant figure, resulting in a specific number of
decimal places . The precision to which raw data is stated is determined by the number of
decimal places used for the uncertainty.
Observations: Under the table
g. Justify uncertainty of dependent variable
h. Identify any significant outliers if present, and mention that they will be omitted from data
processing. If no outliers, state not present.
j. Describe any observations (qualitative data) that may enhance the interpretation of the results.
Fill in the observation table with qualitative data. This data should include anything (random
errors, systematic errors) that might impact your final results.
Data
Qualitative Data/ Observations
Description of how this might impact your
data values. Be specific (i.e. cause
values to be larger than they should
have been/ cause data values to be
smaller than they should have been/
cause values to have a lot of variation &
a big standard deviation)
OM
Sugar
O.125
M
Sugar
0.25 M
Sugar
0.5 M
Sugar
Processed Data (DCP Aspect 2)
Table : Include a descriptive table title that summarizes the investigation including the
independent & dependent variables
a. If necessary, process raw data into a form suitable for graphical representation (e.g.
averaging repeated trials, equations, etc.).
b. Recorded in a correctly formatted table .
c Processed data has the same precision as the uncertainty (i.e. the same number of
decimal places as the uncertainty).*
d. Calculates variation within trials by establishing standard deviation.
Presenting Processed Data (DCP Aspect 3)
TITLE (Note: figure titles usually appear above the graph)
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Plot a suitable graph to examine the relationship between the variables (the
independent variable is usually plotted on the x-axis)..
If plot X-Y Scatter Plots
o If a relationship between the variables is apparent, draw a curve or line of bestfit (do not connect points directly).
o If present identify and explain outliers in data
o Both axes are labeled with correct units.
o Underneath graph Include a description of the trend observed under the
graph. Justify nay trends using R-values
If plot Bar graph
o Both axes are labeled with correct units.
o Error bars are correctly drawn
o Error bar values are described under the graph
o Under graph State where the error bars show significant differences or not.
Statistics Test
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Testing Relationships: If the independent variable is numerical/ quantitative/ a measured
value a correlation test was conducted.
o R-values (NOT R2) are clearly presented
o The significance/ meaning of the R-value is stated underneath the X/Y Scatter plot
graph.
Testing differences:
o The correct test was selected (Chi Squared or T-Test)
o Null Hypothesis (stated underneath bar graph).
o Null hypothesis was correctly rejected or accepted based on statistics results (stated
underneath bar graph)..
o In an organized table, all of the following items were clearly presented:
 Degrees of Freedom
 Critical T or Chi squared value
 Calculated T or Chi squared value
 P-value.
Sample Calculations for Processed Data.
Show all sample calculations. Remember Units.
•
Averaging data from repeat trials: (Only one sample for each calculation made with
correct units)
•
Calculation of standard deviation is presented
•
•
% change in mass = (Only one sample for each calculation made with correct units)
% change in length = (Only one sample for each calculation made with correct units)
DISCUSSION, EVALUATION & CONCLUSION (Criteria DEC)
In paragraph form address the following bullet points:
Discussing and Reviewing (DCE Aspect 1)
 Base on your results, clearly answer the investigative question
o Be sure to state which solutions was hypertonic, hypotonic and isotonic relative to
the potato cells.
 Provide data the following data to support your answer
o average data
o Description of trends
o Data from statistical analysis
 significant difference (i.e. p-values, df, chi squared value, t-value, critical t
value, critical chi squared value) ,
 mathematical relationships (R-Values)
 Describe how your findings/ results does or does not relate to/ support current scientific
concepts/ understandings.
 If your data is not supported by current scientific understanding, provide a suggestion to
why it did not (i.e. was there a problem with your procedure, for example, was some
control variable not controlled)
Evaluating Results & Procedure and Suggesting Improvements: (DCE Aspect 2)
 In paragraph 1: Discussion of Precision & Accuracy
o State whether you feel your data was accurate and precise.
o Justify your statement about accuracy using known values or scientific concepts.
o Justify your statement about precision using standard deviation.
 Paragraph 2: Discussion of significant errors in conducting experiment and procedure
o Briefly list all SIGNIFICANT ERRORS in your experiment, that is all errors that would
have SIGNIFICANTLY impacted your accuracy and precision.
o Be sure to CLEARLY Identify the errors that had the greatest impact on your data and
identify the ones that have the least effect on your data.
 Paragraph 3-?: Discussion of impact of error and improvement
o Starting with the error that had the greatest impact on your data.
o Describe specifically how it affected your data (i.e. cause the values to be bigger or
smaller than actual values OR did the error cause a lot of variation in data). Specifically,
and realistically describe how you would improve this error/ problem.
 Additional paragraphs for all significant errors …Do the same thing in paragraph 3 for all
errors mentioned in Paragraph 2.
o ALL SIGNIFICANT ERRORS should have a paragraph describing how they impacted data
and discussion improvements.
 Last Paragraph, State whether you think if another scientist did your experiment if they would
get the same results and/ or trends as you.
o Justify your statements with a reasons.
References cited/ bibliography
All source used in background information should be cited both in the background information
paragraph using MLA in text/ parenthetical citation and they should be cited in your references cited
section using MLA format. In the references cited section, It should be in alphabetical order by authors
last name..
Grading Rubric 32 points total For Data Collection & Processing:
Raw Data Table: 5 points.
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Titles above & outside of the table. Title should clearly describe data.
Headers inside the table/ above the rows with numbers. Headers should have units and label
describe the numbers.
Headers should also contain uncertainty of measurement (+/-1)
Data should not have UNITS next to them . Units belong in the header row above numbers.
All Numbers should have equal/ same number of decimal places that corresponds to uncertainty
Processed Data Table: 6 points.
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Titles above & outside of the table. Title should clearly describe data.
Headers inside the table/ above the rows with numbers. Headers should have units and label
describe the numbers.
Data should not have UNITS next to them . Units belong in the header row above numbers.
All Numbers should have equal/ same number of decimal places
Averages correctly calculated
Standard Deviation correctly calculated
Observation Table: Qualitative observations about accuracy/ precision of data values 2 points
 Relevant observations are made about factors that may have influence data.
 Outliers in Data are identified.
 Uncertainty in measurement(s) is/ are justified
Graphs 1 showing relationships (: If the independent variable is numerical/ quantitative/ a measured
values) 6 Points
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Title should clearly describe data.
X-Axis is the independent variable. With units and a label
Y-axis is the dependent variable. With units and a label
Best fit-line
Scale of graph is appropriate
A paragraph underneath the graph which describes the relationship between the variables.
Graphs 2 showing differences. 6 points
 Title should clearly describe data.
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X-Axis is the independent variable. With units and a label
Y-axis is the dependent variable. With units and a label
Error bars
Scale of graph is appropriate
A paragraph underneath the graph which states the significant differences between the data
sets, and supports this statement by analyzing the error bars.
Statistics Test: 4 points.


Testing Relationships: If the independent variable is numerical/ quantitative/ a measured
value a correlation test was conducted.
o R-values are clearly presented
o The significance/ meaning of the R-value is stated underneath the X/Y Scatter plot
graph.
Testing differences:
o The correct test was selected (Chi Squared or T-Test)
o Null Hypothesis (stated underneath bar graph).
o Null hypothesis was correctly rejected or accepted based on statistics results (stated
underneath bar graph)..
o In an organized table, all of the following items were clearly presented:
 Degrees of Freedom
 Critical T or Chi squared value
 Calculated T or Chi squared value
 P-value.
Sample Calculations: 3 points
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Average & Standard Deviation calculation are clearly shown
All statistical calculations are clearly shown
Other relevant calculations are clearly shown
Grading Rubric 24 points total For Data Collection & Processing -- 24 points total:
Discussing and Reviewing -- 9 points
 clearly answers the investigative question based on accurate interpretation of data - 2 points
 Supports answer with multiple sources of data -- 3 Points
o Provides average data (Must have units)
o Clearly states whether differences in averages are significant.
 Discuss error bars/ standard deviation and overlap in data
 Above statement is supported with p-values, df, chi squared value, t-value, critical t
value, critical chi squared value)
o Clearly describes the mathematical relationship and supports with R-values
 Clearly & Accurately describes how findings/ results does or does not relate to/ support current scientific
concepts/ understandings – 2 points
 If data was not supported by current scientific understanding, a suggestion to why it did not is provided - 2
points
Evaluating Results & Procedure and Suggesting Improvements: 15 points
 Accuracy & Precision (4 points)
o Statement about the data’s accuracy (1 point)
o Statement about the data’s precise. (1 point)
o Statement justifying accuracy using known values or scientific concepts. (1 point)
o Statement justifying precision using standard deviation. (1 point)
 Errors (3 points)
o All SIGNIFICANT ERRORS in experiment are identified (2 points)
o Error are ranked in order of greatest impact to order of least impact (1 point)
 Improvements (4 points)
o A description of the specific impact was made with every error in experiment.
o A realistic and specific suggestion for improvement of all errors mentioned
 Repeatability (4 points)
o Statement about if another scientist did your experiment if they would get the same exact results (1
point)
o Statement about if another scientist did your experiment if they get the same overall trends. (1 point)
o Justify your all statements with reasons. (2 points)