Osmosis lab report
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Transcript of Osmosis lab report
AFFECT OF CONCENTRAT ION ON
THE RATE OF OSMOSIS
Prepared for:BIOLOGY
Prepared by: ABDULLRHMAN ZAKI
Date:1/12/2012
:
Osmosis InvestigationAim:
The aim of this experiment is to investigate the effect of
changing the concentration of sucrose on the rate of
osmosis in cylinders of potatoes.
This would happen by using similar sizes and lengths of
potato cylinders and applying them into different
concentrations of sucrose (0,10%, 30%, 50%, 70%) in test
tubes then measuring the change in mass of the potato
cylinders afterwards. Maintaining all variables unchanged
such as the pH, same size, and a constant temperature.
The time taken for all potato cylinders will be 30 minutes.
Hypothesis:
I predict that if the potato cylinders where put in a sucrose
concentration where the water potential is higher than the
water potential that of the potato it self that would cause
the mass of the potato to increase and if they had similar
water potential there will be no change in mass.
Scientific Background:
Osmosis is the movement of water particles (molecules)
from a high water potential to a low water potential
through a semi permeable membrane. Many factors affect
the rate of osmosis including size of particle and
temperature however the factor investigated today is
concentration of sucrose.
As the concentration of sucrose increases the difference in
mass of potato will increase since sucrose is a hypertonic
solution which means that it has a higher amount of
particles dissolved in the solution, while a hypotonic
solution such as water where there is fewer particles
dissolved.
When the potato is put in sucrose concentration where the
water potential is greater than that of the potato the
particles will move from the potato to the sucrose then a
decrease in mass will happen
While if it is put in a concentration where they have the
same water
Potential this solution is called isotonic
Variables:
Independent Variable:
The Concentration of sucrose solution in which the potato
cylinder is placed in. (0%, 10%, 30%50%, 70%)
Dependent Variable :
The change in mass (grams) of the potato cylinders before
and after the experiment
Controlled Variables:
SA/V Ratios:
Variable Reason? How to control it?
To be able to balance different SA/V ratio to limit its effect
on the rate of osmosis one must first measure the sizes
using a ruler (±0.1 cm) as well as using a cork borer to
maintain the same diameter for each cylinder but
changing the length of cylinders themselves.
Temperature:
Temperature is one of the factors that affect osmosis, due
to the existence of more kinetic energy as temperature
increases meaning more effective collisions so we start by
Using room temp to maintain the same set temp for each
investigation performed by using a thermometer to
monitor.
Type of tissue:
The type of tissue has a certain effect on rate of osmosis
since the amount of glucose in each type of tissue differs
This will be controlled by using only one type of tissue
which is the same potato
Materials:
2 Large Potato Pieces
1 Cork Borer (0.9 c)
1 Scalpel
1 White Tile
1 Clear Plastic ruler (±0.1 cm)
25 test tubes (UNCERTAINTY) unknown*
120 ml of distilled water
5 Stopwatches (± 0.1s)
Electric balance (± 0.1s)
1 weighing bottle
4 Sucrose solutions (10%, 30%, 50%,
70%)
1 marker
Method:
Using the cork borer remove twenty five potato cylinders
from the potato pieces
Place each cylinder on the tile
With the use of the ruler as well as scalpel, cut cylinders
into 5.5 cm s each
Place each cylinder into a weighing bottle
Measure each potato’s initial mass with the use of the
electric balance
Record results of each different concentration of potato
Place the measured potato cylinders into different test
tubes
Label each test tube with the concentration of sucrose
being tested in it, Apply 10 ml of (0% ) sucrose
concentration (distilled water) to 5 test tubes that have
potato in them and then repeat the same procedure by
adding 10 ml of 10% sucrose concentration, 5 different
and so on for the rest of the concentrations until 25 test
tubes are filled with bead potatoes and different sucrose
concentrations (5 of each concentration)
Data collection :
Sucrose concentration %
(±0.1mm)
Potato (cylinder) mass( ±0.01g)
Initial Final
Exp 1 Exp 2
Exp 3
Exp 4
Exp 5
Exp 1
Exp 2
Exp 3
Exp 4
Exp
Distilled water
1.91 1.90 1.75 1.70 1.91 1.92
2.00
1.79
1.76
1.93
10.0)%( 1.69 1.75 1.68 1.65 1.53 1.61
1.55
1.59
1.65
1.46
30.0)%( 1.69 1.79 1.78 0.89 1.48 1.51
1.37
1.47
1.21
1.46
50.0)%( 1.60 1.61 1.33 1.49 0.97 1.23
1.19
1.01
1.12
0.35
70.0)%( 1.44 1.69 1.54 1.77 1.58 1.07 1.24 1.18 1.32 1.16
Table 1:
Shows the results of each Exp (experiment) with each of the
concentrations of sucrose.
Immediately begin timing the experiment with the
stopwatch for 30 minutes
When the 30 minutes have finished, take out the cylinders
With a paper towel slightly dry the potato cylinder
Once again place each potato cylinder in the beaker
seperately and record final mass
Construct a table for collection of raw data, and record the
initial and final mass of each different size of tissue
*Repeat these steps for each of the concentrations to
record accurate results.
Qualitative data:
The potato cylinders fizzed small air bubbles in the distilled
water cylinder and another thing that was noticed was that
potato became more dull when place is distilled water thusly
changing its color and I can briefly tell by pre measuring and
estimation before measuring with a ruler that as concentration
of sucrose increased the size of the potato decreased making
the size of the potato, which was placed in distilled water the
biggest in size.
Data Processing:
After having collected the data from the experiment the data
will be processed.
As seen previously for each trial we had a different initial and
a final weight the difference that was calculated as seen in
graph 1.
-The difference in mass was calculated by subtracting the
final mass from the initial mass.
The change in mass must be calculated to be able to find out
the percentage change in mass for every potato cylinder for
each of the 5 trials
Producing the results one must first find the change in mass for
every potato cylinder and that can be done by dividing it by the
initial mass and then multiplying it by a 100 this is how it will
look like:
= ∆ mass x 100
Taking Distilled water for an example of the five trials:
Percentage change in mass of the potato cylinder in
experiment 1
∆ =mass x 100
Initial mass of potato
=0.04 x 100/1.75 = 2.29%
Percentage change in mass of the potato cylinder in
experiment 2
= ∆ mass x 100
Initial mass of potato
=0.01 x 100/1.91 = 0.52%
Percentage change in mass of the potato cylinder in
experiment 2
= ∆ mass x 100
Initial mass of potato
=0.1×100/1.90=5.23%
Percentage change in mass of the potato cylinder in
experiment 2
=∆ mass x 100
Initial mass of potato
=0.06×100/1.70=3.53%
Percentage change in mass of the potato cylinder in
experiment 2
=∆ mass x 100
Initial mass of potato
=0.02×100/1.91=1.05%
In order to calculate the change in the mass of each
potato cylinder we must calculate the change in
percentage of the potato cylinders to find the average
change in mass for the potato cylinders in different
sucrose concentrations.
To find the average percentage add the % change of the
mass in experiment to the % change in mass of the
potato cylinder in experiment 2 and 3 and 4 and 5 and
then / them all over 5. Taking distilled water as an
example for all the experiments:
Average percentage change in mass=
Percentage change in mass in experiment 1 +
percentage change in mass in 2+3 +4 +5
=0.52+5.23+2.29+3.53+1.05 =2.52%.
Average percentage change in mass for the potato cylinders in
the 5 different sucrose concentrations is put in to show the rate
of osmosis in the potato cylinders for the sucrose
concentrations.
Sucrose concentrati
ons (%) (±0.1mm)
The difference in mass % change and the average change in mass (±0.1g) for each of
the 5 concentrations)%(
Trial 1 Trial 2 Trial 3 Trial 4 Trial 5
∆
Mass
%
Chang
e in
mass
∆
mass
%
Chang
e in
mass
∆
Mass
%
Chang
e in
mass
∆
mass
%
Chang
e in
mass
∆
Mass
%
Chan
ge in
mass
Average percentage change
0.0)%( 0.01 0.52 0.10
5.23 0.04 2.29 0.06 3.53 0.02
1.05 2.52
10.0)%( -0.08
-4.73 -0.02
-11.43
-0.09
-5.36 0.07 -4.24 -0.07
-4.58
-6.07
30.0)%( -0.18
-10.65
-0.34
-23.46
-0.31
-17.42
-0.28
-24.45
-0.22
-14.35
-18.07
50.0)%( -0.37
-23.14
-0.42
-26.09
-0.32
-24.06
-0.37
-24.83
-0.45
-27.90
-25.20
70.0)%( - - - - - - - - - - -25.52
0.37 25.69
0.45
26.63
0.36 23.20
0.45 25.42
0.42
26.58
Table 2: The percentage change in mass in the 5 experiments,
the average percentage changes in mass of the potato
cylinders for each of the 5 different sucrose concentrations.
The Standard deviation for the experiments was calculated
using Microsoft excel:
The most accurate experiment was for sucrose concentration
(70 %) as it had the standard deviation of 1.353045.
Table3:
S.D for each change in % in (grams)
Standard deviation in (g) for each average percentage change in (g).
Concentration of sucrose(%) Average percentage change (g)
(±0.1)
Standard deviation (g)
0.0 2.52 1.9110.0 -6.07 3.0230.0 -18.07 5.9050.0 -25.20 1.8670.0 -25.52 1.35
Data Presentation:
Graph 1: The effect of the 5-sucrose concentration on the
average percentage change in the mass of the potato cylinders.
0 01 02 03 04 05 06 07 08
03-
52-
02-
51-
01-
5-
0
5
570739462686999.0 = ²R
esorcus 5 eht fo tceffe ehTva eht no (%) snoitartnecnoc - ni egnahc egatnecrep egare
eht fo (g1.0±)(%) ssam ehtsrednilyc otatop
noitartnecnoc esorcus
ssam
ni
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ah
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gatn
ecr
ep
eg
are
va
Conclusion:
To wrap this experiment up I can say that the trails that
were done on each of the 5 different concentrations were
repeated for each concentration 5 times for higher accuracy.
When doing this experiment I was able to see the effect of
different concentrations on the rate of osmosis, each trail
was done by measuring the initial mass of the potato
cylinder and after osmosis, the results that were conducted
shows that as the sucrose concentration increases the rate
of osmosis also increases thusly making a direct decrease in
mass .
A good example would be the experiments with the
concentrations of 10% and 70% concentration results to
show the change. In the 10% concentration I noticed a
decrease in the percentage change in mas for experiment 1
the percentage decrease was -4.73 while for the
concentration of sucrose 70% the change was -25.69 we can
see that the percentage of change in mass is decreasing
thusly we can conclude that the difference of the initial from
the final and as it gets greater that means the mass of the
potato changed massively
According to the osmosis theory as the concentration of the
sucrose solution increases the particle’s water potential
increases and becomes higher than the particles that are inn
the potato .
While in the experiment of the distilled water it was a little
different since the water potential is higher than those in the
potato thusly the mass of the potato cylinders increased.
As seen the in the graph as the curve cuts the x-axis both
the concentration and differences in mass of the potato
cylinders are the same, thusly making the solution an
isotonic solution which means that the water potential of
concentration is similar to the water potential concentration
of the potato cylinder.
So we can see that osmosis cannot take place since it is a
movement from high to low water potential and in this case
they are both equal\ .
According to the experiments I have done and the data I was
able to extract I can say that my hypothesis was supported
by the collected data, which is as the concentration of
sucrose increases the rate of osmosis increases.
The Standard deviation was calculated through mac iWork,
which was able to show the reliability of the data that was
collected and have the ability to see the range of errors
using the error bars.
I was able to see that the standard deviation was different
from one concentration to the other as in distilled water ;
The standard deviation was 1.91(g), while for the
concentration of 10 % it was 3.02(g) and for the
concentration of 30 %, which is the highest, it came about
5.90(g) and finally for the concentration of 70 % that was
the lowest 1.35-(g)
Evaluation:
In the investigation I had a wide range of errors that I
wasn’t able to control as in the temperature of the
surroundings as the room temperature and that could
have manipulated the results in a slight way yet it wont
make the a experiment a fair one.
Another factor would be that the sugar around the potato
pieces might not have been distributed equally so each
potato cylinder my have contained a different amount of
sugar thusly affecting the rate of osmosis.
Another thing that would have caused some error in the
experiment is that the experiment required more than one
piece of potato thusly 2 needed to be used and that gives
us 2 different sources of sucrose and each piece of potato
might have had a different amount of nutrition thusly
affecting the amount of sugar in each so that might have
affected the results of the experiments that were
conducted.
Improvements:
I suggest that if possible a way to make the experiment
better would be by the use of one source of equally
distributed sucrose source and a controlled room
temperature to maintain more reliable results .
Bibliography
"Lab Help for Ex. 6 Green Plant - II." Lab Help for Ex. 6 Green
Plant - II. N.p., n.d. Web. 29 Nov. 2012.
(A person using the cork borer to extract a potato cylinder)