What is the effect of different concentration of salt solution on the rate of osmosis in solanum tuberosum (potato)?

by alsace (student)

International Baccalaureate Biology

Biology Internal Assessment

IB Biology- Internal Assessment Lab Report

Osmosis experiment- Solanum tuberosum (Potato)

Research Question:

What is the effect of different concentration of salt solution on the rate of osmosis in solanum tuberosum (potato)?

Hypothesis:

The potato will lose weight and become shrank when they are put in salt solutions. The higher concentrated the solution, the more the potato shrinks.

Osmosis is the passage of water at a cellular level from an area of low solute concentration to an area of high solute concentration through a membrane along a concentration gradient in order to equalize the level of water in each region. When potato strips are placed in concentrated salt solutions, they lose water by osmosis and they become "flaccid". They become swollen and hard. When the salt solution becomes more concentrated, more water would move out from the potato by osmosis.

Variables and Fair Testing:

The control variables are kept constant to ensure a fair test. I will also use a pure water solution as a control in this experiment.

Apparatus:

5 beakers of 500ml
Potatoes
Electronic scale to 2 d.p.
Distilled water
Cutting board
Ruler
Stopwatch
Paper towel

Method:

Cut potato into strips by borer to 3.0cm long. Prepare 25 of them.
Prepare 5 different concentration of salt solutions with NaCl and 50ml of distilled water each in the beakers and label them as below:

Table 1 - ...

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Variables and Fair Testing:

The control variables are kept constant to ensure a fair test. I will also use a pure water solution as a control in this experiment.

Apparatus:

5 beakers of 500ml
Potatoes
Electronic scale to 2 d.p.
Distilled water
Cutting board
Ruler
Stopwatch
Paper towel

Method:

Cut potato into strips by borer to 3.0cm long. Prepare 25 of them.
Prepare 5 different concentration of salt solutions with NaCl and 50ml of distilled water each in the beakers and label them as below:

Table 1 - NaCl-H2O Dilutions

Repeat Step 4. for 1.00M, 2.00M, 3.00M and 4.00M concentration solutions with 5 strips each.
After 24 hours, place the potato strips again on the scale and work out the percentage change.

Data collection:

Table 2- Raw Data Table – Mass of Potato Strips – Pre- & Post-Experiment

Qualitative Data - Before Experiment

The potato strips are generally rigid in structure.

All the potato strips appear similar

Qualitative Data - After Experiment

All the potato strips have shrunken in size and have reduced lengths.

Strips immersed in 4.00M NaCl solution have become very soft and soggy.

Quantitative Data

The data I collected from the experiment is shown below where it shows the percentage change in mass of the potato strips after they are immersed in different concentration of salt solutions.

Table 3 - Processed Data Table – Difference between % Change in Mass and Average % Change in different concentration of salt solutions

Graph 1- The above average and standard deviation are plotted in the graph below to show the relationship to the percentage change in the mass of potato strips.

Conclusion

In conclusion, the results indicate that the concentration of salt solution have a correlation with the percentage change in mass. Graph 1 supports this theory.

The higher the concentration of salt solution, the larger the percentage change in mass of potato strips. (The y-xis is in negative figures).

The results for my control experiment did not turn out as I predicted. Instead of swollen, the strips also shrank after 24 hours in distilled water.