Osmolarity of Solanum tuberosum Investigation
Research Question:
How can we estimate the osmotic pressure of potato cells by soaking them in a
solution of NaCl at different concentrations and calculating the percentage change in
their mass?
Hypothesis:
Osmosis is the net movement of water through a partially permeable membrane. From
a high water potential to low water potantial down a concentration gradient. The
osmotic concentration of the cell cytoplasm in potatoes is usually between 0.4 –
0.6M/dm³. My hypothesis is that, as the salt concentration of the solution became
increasingly more diluted, the potatoes will become increasingly heavier in
comparison to their prior form. A hypertonic solution has a higher concentration of
solute than the solution it’s being compared to. While, the hypotonic solution has a
lower concentration of solute than the solution it’s being compared to, and the istonic
point could be found between the hypotonic and hypertonic region. Since the diluted
concentration of NaCl in comparison with the water inside the cells, there is a higher
concentration of water outside of the cell, with osmosis the water will enter the cells
to balance out the concentration which made them heavier than usual.
Materials:
Six 150 ml beakers .
Distilled water
Salt (NaCl)
Potato
Cork borer
Knife
Weighing balance
Glass rod
Ruler
Method & Procedure
1. Label six 150ml beakers as 0.0M, 0.2M, 0.4M, 0.6M, 0.8M, 1.0M
2. Prepare salt solution of concentrations 0.0M, 0.2M,0.4M,0.6M,0.8M,1.0M in
the beakers labelled by following the given method :
3. Cut 6 potato cylinders using the cork borer to length 2cm (to be as accurate as
possible!). Remove any skin from the cylinders.
4. Find and record the mass for each potato cube and record in Table 1
under “Initial Mass.”
5. Place a potato cylinder in each beaker after recording their initial mass.
6. Ensure that all potato cylinders are completely submerged; add an equal
amount of solution to all beakers if one cylinder is not submerged.
7. After 40 mins, take the potato cylinder out of the 0.0 Molar Solution beaker
and carefully blot dry with a paper-towel.
8. Find and record the 0.0 Molar potato cylinder mass under Final Mass in Table
1.
9. Repeat Steps 7 and 8 for each of the remaining saline solutions.
10. Calculate the percent change in mass for each of the solutions:( (Final
Mass-Initial Mass)/Initial Mass) x 100%
Variables:
Table 1 (Independent Variable&Dependent Variable)
Variable
Unit
Why to Control
Independent
Variable:
Concentration of
NaCl solution
M/dm³
Dependent
Variable: %
Change in mass
g
How it was
controlled
6 variation of NaCl
concentration: 0.00,
0.2, 0.4, 0.6, 0.8,
1.0mol/dm³.
Changing the
osmotic
concentration of
the NaCl solution
will present the
influence it has on
the percentage
change in mass,
which compares
the concentration
variatins to each
other.
So the percentage The initial mass
change in mass can should be measured
be calculated
and the final mass
should be measured
after being in the
solution for 40
minutes using a
digital mass scale.
Table 1.1. (Controlled Variable)
Variable
Unit
Volume of solution
Size of beaker
cm³
100cm³ beaker
Size of Solanum
tuberosum
cm
Time in solution
s
Why to Control
To ensure accurate
results, since if the
water volume
changes, the
concentration of
NaCl solution will
change too which
will affect the
results.
The water volume
should be the same
volume of beaker
decreasing
inaccuracies in
results
The size of
Solanum
Tuberosum had to
be controlled the
same so the change
in mass can be
accurate, leading to
reliable results. The
variation in surface
area can affect
osmosis result
If the Solanum
Tuberosum doesn’t
stay in each
solution for the
same exact time in
each experimental
trial, the results are
inaccurate.
How it was
controlled
100cm³ of solution
has to be used in
every concentration
of NaCl solution.
100 cm³ beaker has
to be used in every
concentration
Cut with scalpel
using caliper 2cm
Each Solanum
Tuberosum needs
to stay in the
solution for 2400s
(40mins)
Safe ethical and environmental issues:
Sodium chloride is not harmful, however there are specific first aid protocols for
handling the material. The safety data sheet states that after inhaling NaCl, the
person should breathe fresh air. The person should remove any contaminated
clothing and wash or rinse off with lots of water after making skin and eye
contact. If ingested, the person should drink two glasses of water right away and
see a doctor if they feel ill. After handling the material, hands should be
immediately cleaned . It is important to handle the scalpel and borer cautiously
and keep them away from the body. Holding the potato in one hand will prevent
the scalpel and borer from approaching the hand. The instructor should be
notified right once if someone is hurt in any way. Glass should be handled
carefully; if it breaks, get in touch with the instructor. Although the materials
used in this experiment should be disposed of properly, there is no direct
environmental impact. Because of its solubility, NaCl should be disposed of in
an area where runoff will escape in order to protect the environment. To lessen
the harm to the environment, just a little amount of tissues should be used, and
the materials should be recycled and used again.
Multiple Trials:
Figure 1.Raw Data
Sample Calculation:
-Change in Mass Sample Calculation
Formula: Δmass = final mass - initial mass
-Percent Change in Mass Calculation
Formula: %Δmass = (Δmass/initial mass) x100%
-Standard Deviation Calculation using Excel
Formula: σ = sqrt [ Σ ( Xi - X )2 / N ]
-Mean Percent Change in Mass
Formula: (sum of all trial value)/(number of trials)
Processed Data Table
Figure 2.1. Percent Change in Mass
Figure 2.2. Mean Percent Change in Mass
Figure 2.3. Mean Percent Change in Mass +30%
Table 3. Qualitative Data
NaCl Concentration
0.0 M/dm³
Qualitative Data
Potato cylinder remains turgid, no significant change in
texture or size.
0.2 M/dm³
Slight decrease in mass, potato slightly softer but still
turgid.
0.4 M/dm³
Noticeable decrease in mass, potato becomes more
flaccid.
0.6 M/dm³
Significant decrease in mass, potato shows clear signs
of dehydration and shriveling.
0.8 M/dm³
Substantial loss in mass, potato is very soft and
shriveled.
1.0 M/dm³
A little heavier than 0.80 M’s potato cylinder, the
potato is almost collapse hard to handle
Data Analysis:
A descending trend of percentage change in mass is visible in Table 2.2. indicating
that as the concentration of NaCl increases, the mean percentage change in mass
decreases until it begins to become unchanged as shown by the decreasing percent
change in mass from 0.6 to 1.0M/dm³. This showed that when the concentration
reaches around 0.8M/dm³, the effect of NaCl on Solanum Tuberosum is not effective
anymore. The data also presents the mass of Solanum Tuberosum rises when attach
with a solution with a concentration around 0.0-0.1 M/dm³, as it is above x-axis,
signifying a positive percent change in mass. thus, below the x-axis, signifying a
negative percent change in mass.
Figure 2.3. shows the mean percentage change in mass shifted up by 30% for
analytical purposes. The quadratic trend line visualizes the decreasing trend in mean
percentage change in mass of Solanum Tuberosum discussed for Figure 2.2. The R²
value is 0.9955 meaning the the data points are very close to the quadratic trend line,
there are tiny differences between the observed data and the fitted values around the
regression line. The data point of 0.6 M/dm³ NaCl concentration is the greatest outlier,
indicating that the greatest outlier which means that the data is less valid as it is the
furthest from the quadratic trend line for this experiment.
Standard deviation shows the distance between the mean and each data point. The
further the data points for each variation from the mean, the higher the standard
deviation. The 0.0 M/dm³ of NaCl concentration has a relatively low standard
deviation of 2.92%, represents a relatively reliable data. The 0.2 M/dm³ of NaCl
concentration has a lower standard deviation meaning a more reliable data than 0.0
M/dm³. The 1.0 M/dm³ has the highest standard deviation of 4.99%, illustrating the
data point is far dispersed so the data for this concentration is the least reliable. The
remaining variations have a standard deviation of 2.73% to 4.07%, indicating the data
are reliable.
Conclusion:
The hypothesis“as the salt concentration of the solution became increasingly more
diluted, the potatoes will become increasingly heavier in comparison to their prior
form. ”isn’t supported by the data. This can be seen in Table 2.2. where the percent
change in mass of the Solanum Tuberosum decreases as the concentration as the
concentration of NaCl increases (From 0.0-0.8M). At the beginning, the percent
change in mass is positive, as shown by the data point of variation with the 0.0 M/dm³
NaCl concentration plotted above the x-axis, and then becomes negative as the NaCl
increases for the remaining 5 variations. The downward sloping quadratic trend line in
Figure 2.2. also shows the descending percentage change in mass as the NaCl
concentration increases. The osmolarity is the total solute concentration in a given
volume of a solvent. The greater concentration of solutes, the higher the osmolarity.
Compare to water which has an osmolarity of 0, Solanum Tuberosum has a high
concentration of solutes.
The result of the experiment are almost all reliable because of small deviation values
as showed in Figure 2.1. Although the variations with 0.4, 0.8 and 1.0 M/dm³
NaCl concentration have slightly higher standard deviation values between 3.28% to
4.99%, but the data points are still close to the quadratic trend line, representing that
there are no significant outliers in the data collected, revealing that the results are
accurate.
Scientific reasoning also supports the data collected from this experiment. When the
osmotic concentration of the NaCl solution increases to the isotonic point of the
Solanum Tuberosum cells, and becomes hypertonic, the mass of Solanum Tuberosum
will decrease. This is because of water moves from the inside to the outside of the
cells. A change in mass of potato cells can be interpreted as the net movement of
water across the phospholipid bilayer into the cells. At lower concentrations of NaCl,
the water enters the Solanum Tuberosum by osmosis, indicated by a negative mean
percentage change in mass in Figure 2.1. There is higher water potential in the
Solanum Tuberosum compared to the solution; the solution is hypertonic to the
Solanum Tuberosum.
Evaluation:
Inaccurate NaCl Solution Preparation: Accurate measurements of the salt and water
are necessary for the creation of NaCl solutions. The osmotic gradient and the flow of
water into or out of the potato cells would be impacted by an imprecise concentration
of NaCl in the solutions, producing incorrect findings. The findings might have been
skewed by solutions that were either more concentrated or diluted than anticipated
due to minor errors in the salt measurement or the amount of water used.
Minimizing the error: The precision of the concentrations would be increased by
preparing NaCl solutions in volumetric flasks rather than beakers. Because volumetric
flasks are made for exact measurements, this would lessen the possibility of mistakes
resulting from improper dilution. Further lowering the possibility of incorrect solution
preparation would be achieved by precisely weighing the NaCl salt using a digital
balance and making sure the balance is calibrated before use.
Environmental Elements (Humidity and Temperature): Variations in humidity and
temperature may have affected the experiment's osmosis rate. Since osmosis is a
temperature-dependent process, water moves more quickly at higher temperatures.
Results may have been inconsistent due to changes in humidity or room temperature,
particularly if these variables were not managed during the experiment.
Minimizing the error: The experiment should be carried out in a
temperature-controlled room, ideally within a small range (e.g., 20-25°C), to account
for environmental factors. To further evaluate its possible impact on the outcomes, it
would be helpful to note each NaCl solution's temperature at the beginning and
conclusion of the experiment. The experiment might also be carried out in a
humidity-controlled setting, or at the very least, by guaranteeing constant exposure to
air.
Human Error in Handling (Blotting and Weighing): Although it is crucial to wipe the
potato cylinders dry before determining their ultimate mass, variations in the amount
of moisture removed from the surface might result in inaccuracy. For instance, there
can be minor variations in the bulk of the potato cylinders depending on how
completely they were blotted. Additionally, human error during the weighing
process (e.g., not ensuring that the balance reads zero before weighing, or not
properly handling the potatoes) could have affected the accuracy of the
measurements.
Minimizing this error: A more standard blotting method, such pressing the potato
cylinders in the same way for the same length of time or using a certain quantity of
blotting sheets, might be used. Furthermore, there would be less chance of moisture
being transferred from the hands to the potato if the potatoes were handled using
tongs or tweezers. A digital scale with automated tare features would reduce human
mistake during the weighing process, and it is essential to make sure the weighing
balance is correctly zeroed before each measurement.
Strengths&Weaknesses/Limitations:
Table 4. Strength of the method
Strengths
Number of Trials
Percise Measuring Equipment
Clear Trend Observed
High R² Value
Scientific Basis
Significance
For each of the six variations five trials
were completed which assures that the
error and uncertainty are smaller so the
results are more reliable.
The measuring equipment used was
chosen due to the accuracy it ensures.
The 100mL measuing cylinder was used
to measure NaCl solution, has an
uncertainty of ±1.0 cm³. The ruler was
used to measure the length of Solanum
Tuberosum cylinder, and has an
uncertainty of ±0.1cm.
The experiment successfully
demonstrates a clear decreasing trend in
percentage change in mass relative to
NaCl concentration, providing a strong
visual representation of osmotic
principles.
The R² value of 0.9955 indicates a strong
correlation between data points and the
quadratic trend line, suggesting that the
results are reliable and closely fit the
expected model.
The experiment is grounded in sound
scientific principles regarding osmolarity
and osmosis, which enhances the
credibility of the findings.
Table 4.1. Strength of the method
Weaknesses/Limitations
Potential for Evaporation
Standard Deviation
Significance
The solution were left uncovered,
evaporation could have altered the
concentrations over time, affecting the
results.
While some variations showed low
standard deviations, the higher values at
certain concentrations indicate potential
inconsistencies in the data.
Limited Concentration Range
The range of NaCl concentrations
investigated may not fully reveal the
osmotic behavior if Solanum Tuberosum,
particularly at higher concentrations.
Random Error - Reading Measurements When
students
read
different
Incorrectly
measurements, random error can occur
and the data will become less reliable.
Random Error - Condition of Solanum Such as when Solanum Tuberosum has a
Tuberosum
high concentration of water there is likely
to have a greater net movement of water
out of the phospholipid layer. Therefore,
leading to a greater percentage change in
mass and inconsistency in the results.
Improvements:
1. Standardization of Sample Preparation: To minimize variations in mass and surface
area, establish a procedure for chopping potato samples to consistent sizes, maybe
with the use of a mechanical cutter.
2. Controlled Environment: Use water baths to ensure constant solution temperatures
during the experiment and carry out all experiments in a temperature-controlled
setting.
3. Accurate Timing: To guarantee that every sample is exposed to solutions for the
same amount of time, use a digital timer and a predetermined methodology for
immersion periods.
4. Accurate Concentration Verification: Use more accurate measurement tools, such
as volumetric glassware and analytical balances, and think about utilizing a
refractometer to evaluate the concentration of solutions.
5. Reduce Evaporation: To stop the solutions from evaporating during the experiment,
use covered containers or conduct it in a confined space.
Bibliography:
https://www.ehs.com/2015/04/safety-with-salt-sodium-chloride-safety-information/
https://about.dataclassroom.com/ready-to-teach/potato-osmosis-lab
http://www.curiouscience.com/uploads/3/7/4/1/37410239/ib_lab_report_guide_edited
_for_mws.pdf
https://stattrek.com/statistics/dictionary
https://statisticsbyjim.com/basics/standard-deviation/
https://www.coursehero.com/file/173518608/G11-Osmosis-Lab-Report-Jiseop-Leepdf
/