Effects of Changing Solution Concentration on Osmosis

Part 1 :Introduction

Problem statement:

Students will be able to investigate the effects of distilled water and different concentrations of sugar solutions on the length of potato chips.

Hypothesis:

If the solution that the potato chip will be in has a high concentration of water, then the potato chip will increase in size/length. If the solution that the potato will be in has a low concentration of water, then the potato chip will decrease in size/length.

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Explaining the hypothesis:

The process of osmosis states that molecules move from a higher concentration to a lower concentration. Because of this, when the solution has a high concentration of water, the molecules in the solution will move to the potato chip, which has a low concentration of water, increasing its size. However, when the solution has a low concentration of water, the molecules in the potato chip move to the solution, which has the lowest concentration of water, decreasing its size.

Dependent Variable:

Change in length of the potato chips.

Independent Variable:

The solution the potato chips are placed in.

Controlled variables:

1. The length of the potato chips used.
2. The amount of solution the potato chips were placed in.
3. The temperature of the room.
4. The test tubes where the solutions were poured.

Equipment:

1. Cork Borer.
2. Potato.
3. Dropper.
4. Three test tubes.
5. Whiteboard marker.
6. Knife or other sharp objects.
7. Tweezers or toothpicks.

Procedure:

1. Use the cork borer to cut three pieces of the potato.
2. Cut each piece of the potato chip using a knife to the same size.
3. Record the length of the potato chips in the table in your lab report.
4. Fill the three test tubes with: Distilled water, weak sugar solution, and strong sugar solution.
5. Prepare a timer for 15 minutes on your Chromebook or watch.
6. Drop each potato chip into a different test tube at the same time.
7. Start the timer as soon as the potato chips are dropped into the test tubes.
8. Wait 15 minutes.
9. Take the potato chips out of the test tubes using tweezers or toothpicks and place them on a clean surface.
10. Measure the length of each potato chip and record it in your table in your lab report.
11. Dispose of the potato chips and the solutions in a clean and orderly manner.

Part 2 : Data Collection and Data Processing

Data Collection:

• Test tube
• Liquid in test tube
• Original length of potato chip (cm)
• Final length of potato chip (cm)
• Change in length of potato chip (- or + cm)

A

Distilled water (10mL)

• 3.5cm
• 3.7cm
• +0.2cm

B

Weak sugar solution (10mL)

• 3.5cm
• 3.5cm
• 0cm

C

Strong sugar solution (10mL)

• 3.5cm
• 3.1cm
• -0.4cm

Draw column graph showing type liquid in the test tube on the x-axis via the change in length of potato chip (cm ) on the y-axis.

Part 3 : Conclusion and Evaluation

Q1: Which chip has increased in size? Explain what has happened.

A1: The potato chip that was placed in distilled water has increased in size. Using the process of osmosis, we can explain why this happens. In simple terms, according to the GCSE 5th edition biology book, “Osmosis is the movement of water molecules from an area of high water concentration to an area of low water concentration across a partially permeable membrane”. In this experiment, when the chip was placed in distilled water, the solution had a higher water concentration than the chip, which caused osmosis to take place. Water molecules from the solution passed through the partially permeable membrane of the potato into the chip, causing the chip to increase in size. The greater the number of molecules in an object, the larger its size will be. It's important to note that the process of osmosis is known as a special kind of diffusion, which is why both these processes are quite similar.

Q2: Which chip has decreased in size? Explain what has happened.

A2: The potato chip that was placed in a strong sugar solution has increased in size. Using the process of osmosis, we can explain why this happens. In this experiment, when the chip was placed in a strong sugar solution, the solution had a lower water concentration than the chip, which caused osmosis to take place. Water molecules from the potato chip passed through the partially permeable membrane and into the strong sugar solution, causing the chip to decrease in size. The fewer the number of molecules in an object, the smaller its size will be. Osmosis is extremely similar to diffusion as it is known as a special kind of diffusion.

Q3: Feel the chip from test-tube A. Why does it feel firm?

A3: When the chip was placed in distilled water for 15 minutes, it felt firm, compared to the other chips, and this is due to osmosis. As water molecules exited the solution and entered the potato chip, the chip increased in size, due to it having more molecules. The chip felt turgid and firm because there wasn’t much space between the molecules due to the high amount of them entering the chip, which caused the chip to be cramped and restricted.

Q4: Feel the chip from test-tube C. Does it feel limp?

A4: When the chip was placed in a strong sugar solution for 15 minutes, it felt limp, compared to the other chips, and this is due to osmosis. As water molecules exited the potato chip and exited the strong sugar solution, the chip decreased in size, due to it having less molecules. The chip felt flaccid and limp because there was a lot of space between the molecules due to the high amount of them exiting the chip, which caused the chip to be unrestricted and roomy.

Q5: If a chip has not changed in length, what does this tell you about the liquid in the test-tube and the liquid in the potato cells?

A5: The chip that was placed in a weak sugar solution did not change in length. Using the process of osmosis, we can explain why this happens. If a chip does not change in length, it means that the potato chip and the weak sugar solution have, more or less, the same water concentration, causing them to not go through the process of osmosis. When the solution and the chip have the same water concentration, no water molecules travel from one place to another, as there is no specific high or low concentration in this experiment. This is why the chip did not feel any different than when we began the experiment and when we ended the experiment, and why the chip didn’t decrease or increase in size.

Q6: Conclusion and evaluation.

A6: In conclusion, when a potato chip is placed in a solution with high water concentration, it will increase in size. When a potato chip is placed in a solution with low water concentration, it will decrease in size. After completing the experiment and evaluating my results, my hypothesis turned out to be correct, as I mentioned the effects of solutions with different water concentrations on the length and size of the potato chips. As I mentioned previously, the potato chip increases or decreases in length all because of the process of osmosis, a special type of diffusion.

Q7: What are the weaknesses and the sources of error in this experiment? Discuss.

A7: After completing the experiment, I believe that there are some weaknesses and errors that took place. Firstly, my group used a ruler to measure the length of the potato chip, which is not a precise way of measuring due to human error. In addition, my group used a dropper to measure the amount of solution, which is also not an exact way of measuring due to human error. Lastly, because our class only had one period in the lab, we were not able to do the experiment more than once to confirm our results.

Q8: Suggest improvements to this experiment.

A8: After completing the experiment, I believe that there are some weaknesses that my group could improve with time and the correct tools. Firstly, my group could have used a more precise way of measuring the length of the potato chip, as well as measuring the amount of solution, as a ruler and a dropper is not the most accurate way of measurement, due to human error. My group could also improve this experiment if we had more time to repeat the experiment and have more trials, to confirm our results and evaluate our experience correctly.

Q9: Discuss the validity of this method.

A9: After completing the experiment, as well as reflecting on it in my lab report, I believe that the method that my group and I used was valid. The potato chip method has been used in many schools all around the world as it is a very simple experiment where students can clearly see the effects of osmosis. Overall, this experiment is very clear and direct, which is why it is valid and why our school used it.