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Osmosis Experiment

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Osmosis Experiment

Aim

Ÿ To investigate the effect of osmosis on potato chips in different
concentrations of sugar solution.

Ÿ To find the concentration of sugar in baking and sweet potato

Introduction

Osmosis is the diffusion of water molecules from a high to low
concentration across a semi-permeable membrane.

The process of osmosis is important in plants and takes place in:

Ÿ Root hair cells, where water is absorbed from the soil.

Ÿ Plants cells. If a plant cell is surrounded by water or a solution
more dilute than the content of the cytoplasm and cell sap, water will
pass into the vacuole by osmosis. The vacuole expands and presses
outward on the cytoplasm and cell wall, making the cell turgid. If the
vacuole loses water for any reason, the cells will lose their turgor
pressure and become flaccid. This is useful for support to green
plant tissue and for opening and closing guard cells.

Ÿ Xylem vessels. Water is carried up from the roots to the leaves in
the transpiration stream.

Preliminary Work

Aim

Ÿ Find out which concentrations of sugar will be appropriate for this
experiment.

Method

Ÿ Cut baking potato into 6 pieces to 45mm in length.

Ÿ Label six boiling tubes, three ‘0M’ and three ‘1M’

Ÿ Measure out 20cm³ of 0M and 1M sucrose solution for each boiling
tube. (0M is distilled water)

Ÿ Place potato chips in boiling tubes and leave for 25 minutes.

Ÿ Remove and measure again.

From this experiment I will be able to see at which concentration of
sucrose solution osmosis will take place.


Diagram of Experiment





Results

Conclusion

The potatoes in 0M of sucrose solution gained in length and felt hard.
The potatoes in 1M of sucrose solution decreased in length and felt
flabby.

0M-1M is an appropriate range because osmosis takes place in both
solutions. For the real experiment, I will measure the masses of each
potato chip rather than the lengths for greater accuracy. I will make
sure that the potato chips have the same dimensions and are left for
longer so that osmosis is able to take place. In addition I will
remove any excess water off the potato chips with tissues before the
second mass reading.

Experiment

Apparatus

Ÿ 10 glass vials-20cm³

Ÿ 5 concentrations of sucrose solution - 0M, 0.25M, 0.5M, 0.75M and
1M

Ÿ 2 potatoes-baking and sweet

Ÿ Cork borer

Ÿ Knife

Ÿ White tile

Ÿ Labels

Ÿ Measuring cylinder -25cm³

Ÿ Mass balance


Ÿ Method

Ÿ Label vials with correct concentrations.

Ÿ Measure sugar solutions.

Ÿ Cut out potato with cork borer and measure them to 30mm.

Ÿ Measure the mass of each potato chip before immersing in solution.

Ÿ Put in correct vials.

Ÿ Leave for an hour.

Ÿ Remove any excess water and measure masses again.

Diagram of Experiment

Prediction

I predict that in 0M of sucrose solution, the potato chips will gain
mass. 0.25M is nearer to 0M and so potatoes in that solution should
also gain mass. This is because the water molecules will move from the
solution into the potato due to osmosis, resulting in an increase in
mass. In 1M of sucrose solution the potato chips will lose mass. 0.5M
and 0.75M are nearest to 1M and so the potato should also lose mass.
This is due to the movement of water molecules from the potato into
the solution, resulting in a decrease in mass. The sweet potato will
have the highest concentration of sugar because it is sweeter than
baking potatoes.

Results

Analysis

I have calculated the % change in mass for every potato chip with the
formula:

(Final mass-initial mass) ÷ initial mass x 100

I have measured the % change because it shows the increase or the
decrease from the initial mass, therefore providing a greater accuracy
than just the change in mass.

Gain In Mass

From the graph I can see that both the baking and sweet potatoes at 0M
and 0.25M gained in mass. This is because water molecules diffused
from the higher concentration to the lower concentration due to
osmosis, therefore increasing the mass of the potatoes. The potatoes
in 0M increased by a greater mass than the ones in 0.25M because it is
more concentrated in water and so more molecules diffused from the
solution into the potatoes. Loss In Mass

Both potatoes in 0.5M, 0.75M and 1M lost mass. This is because the
concentration of water in the potato chips was more than the
solutions, so water molecules moved from the potatoes and into the
solution, therefore decreasing the mass of each potato chip.

From my graph I am able to find the concentration of sugar in each
potato by observing where the graph for the potato crosses the x-axis.
The concentration in baking potato is 0.35M and in sweet potato it is
0.47M.

The analysis of my results support my predictions because I predicted
that there would be a gain in mass for potato chips in 0M and 0.25M
and a loss in mass in 0.5M, 0.75M and 1M. I also predicted that there
would be a higher concentration of sugar in the sweet potato.

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"Osmosis Experiment." 123HelpMe.com. 18 Apr 2014
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