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%


experiment 2

= ∆ mass x 100


=0.01 x 100/1.91 = 0.52%


experiment 2

= ∆ mass x 100


=0.1×100/1.90=5.23%


experiment 2

=∆ mass x 100


=0.06×100/1.70=3.53%


experiment 2

=∆ mass x 100


=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

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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)

osmosis lab report

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