Experiment - Osmosis in Potatoes

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Experiment on Osmosis Using Potato Strips

Objective

To demonstrate the occurrence of osmosis in potatoes.

Objective

Variables

• Initial length and thickness of the potatoes
• Amount of water used in the containers

• Final length of the potatoes
• Other physical changes

Controlled Variable

Dependent Variable

Independent Variable

• Salt concentration of the solution used

Variables

Hypothesis

The salt concentration of the solution does not have a significant effect on the final length of the potatoes.

Hypothesis

The salt concentration of the solution has a significant effect on the final length of the potatoes.

Alternative Hypothesis

Null Hypothesis

Prediction of Outcomes

Predicted Outcome

Potato strips that have been submerged in hypertonic solution will decrease in size while the ones submerged in isotonic solutions will retain its size. Furthermore, potato strips that have been submerged in hypertonic solutions will increase in size. This is due to the difference in concentration between the cells of the potato strips and the outside environment which triggers the occurrence of osmosis (Lohner, 2020).

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Materials

Figure 1. Materials of the Experiment

• Potato
• Knife
• 4 Plastic Containers (Uniform Sizes)
• Ruler
• Salt Solution
• Distilled Water
• Measuring Spoon

Materials

Procedure

Step 5

Pour in 2 cups of distilled water, enough to immerse the strips, into the first container. Label.

Procedure

Step 4

Place three potato strips in each plastic container.

Step 3

Prepare three varying concentrations of salt solution, by dissolving ½ tbsp, 2 tbsps, and 4 tbsps of salt in 2 cups of distilled water.

Measure and record the initial length of the potato strips.

Cut 12 potato strips. Make sure those are of uniform thickness and length. Set aside.

Step 2

Step 1

Step 10

Take note of other changes in the potato strips.

Step 9

Compute for the difference in length of potato strips placed in each set-up.

Step 8

Measure the final length of the strips.

Keep the set-ups for 20 minutes.

Pour varying concentrations of the salt solution into three other containers with potato strips. Label accordingly.

Step 7

Step 6

Procedure

Preparation of Materials

The potatoes are sliced into uniformly sized strips. The strips are 5.6 cm in length and 1 cm in width

Results

Table 1 shows the final length of the strips after being submerged in the saltwater solutions. The table also shows the average final length of the strips per container and the difference between the initial and final length of the strips.

Table 1. Final length of the potato strips and their average

Figure 2. Salt Content versus Difference between the Final and Initial Length of the Potato Strips

Difference between the Final and Initial Length (cm)

Salt content (tbsp)

Figure 2 shows the relationship between salt content and the difference between the final and initial length of the potato strips. The figure shows that the two variables has a direct relationship. As the salt content increases, the difference between the final and initial lengths decreases. A positive value of the difference indicates that the length of the potato strip increased after being submerged while the negative value of the difference indicates that the length of the potato strip decreased. Other changes that were observed are the change in crispiness of the strips after being submerged. The potato strips that have been submerged in the container with 2 and 4 tbsps of salt lost their crispiness and are now bendable

Results

Discussion

salt in the used solution, the potato strips expanded. This is because the solution that has been used is a hypotonic solution. This means that the salt concentration is low to none. The hypotonic solution causes the imbalance of the inner and outer environment of the cells within the potato wherein the salt concentration inside the cell is higher than the salt concentration outside. This causes the water to go inside the cell to balance out the concentration, hence increasing the size of the potato strip (Urry, Cain, Wasserman, Minorsky, & Reece, 2017).

The physical changes of the potato strips after being submerged in the solution are due to the occurence of osmosis within the cells. According to Urry, Cain, Wasserman, Minorsky, and Reece (2017), osmosis is the diffusion of water through semi permeable membrane, whether artificial or cellular. This diffusion of water happens to maintain the equilibrium between the inner and outer environments of the cells.In the first container, containing 0 tbsp of

Discussion

and 4 tbsps of salt, respectively, the potato strips shrunk in size. The decrease in the size is caused by the solution being a hypertonic solution. This means that the solution has a high salt concentration and is much higher than the salt concentration inside the cells within the potatoes. This causes the water inside the cell to diffuse out of the cell, causing the potato strips to shrink. This also causes the potato to lose its crispiness and therefore, be bendable (Urry, Cain, Wasserman, Minorsky, & Reece, 2017).

In the second container containing ½ tbsp of salt, the difference in length was negligible. This is due to the solution being an isotonic solution. This means that the solution has a salt content but it is equivalent to the salt content within the cells of the potato strips. The equivalent salt concentration caused little to no diffusion of water to occur, hence no changes are observed in the potato strips (Urry, Cain, Wasserman, Minorsky, & Reece, 2017). In the third and fourth container containing 2

Discussion

Conclusion

The experiment is successful in demonstrating the occurrence of osmosis in potatoes. The results of this experiment agreed in the alternative hypothesis that salt concentration has a significant effect on the final length of the potatoes. The experiment also agreed with the predicted outcome wherein potato strips decrease in size in hypertonic solutions, retain its size in isotonic solutions, and increase in size in hypotonic solutions.

Conclusion

Lohner, S. (2020, January 9). Make a Potato Shrink -- with Saltwater. Retrieved from www.scientificamerican.com: https://www.scientificamerican.com/article/make-a-potato-shrink-with-saltwater/ Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., & Reece, J. B. (2017). Campbell Biology (11th ed.). New York City: Pearson Education, Inc.

References

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