Osmosis_ Determining the Tonicity of Unknown Solutions

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Northern Virginia Community College *

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101

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Biology

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Dec 6, 2023

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docx

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5

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Ocampo 1 Apollo Dion Ocampo Professor J. Sitnik BIO 101-2AYA 6 November 2023 Osmosis: Determining the Tonicity of Unknown Solutions Introduction: In this experiment, we want to determine the tonicity of four unknown solutions (A, B, C, and D) in relation to potato cells by measuring the change in weight of potato cubes placed in each solution over time. Tonicity refers to the concentration of solutes in a solution and its impact on the movement of water across a semi-permeable membrane, such as the cell membrane of potato cells. We hypothesized that the tonicity of each solution would influence the weight change of the potato cubes over time. Hypotheses: Hypothesis for Hypotonic Solution: If the solution is hypotonic, the potato cube will gain weight over time. This is because water will move into the potato cube, causing it to swell as it absorbs water. Hypothesis for Hypertonic Solution: If the solution is hypertonic, the potato cube will lose weight over time. This is because water will move out of the potato cube into the more concentrated solution, causing it to shrink.
Ocampo 2 Hypothesis for Isotonic Solution: If the solution is isotonic, the potato cube's weight will remain relatively constant over time. This is because water will move in and out of the potato cube at an equal rate, maintaining its size and weight. Materials and Methods: 1. Four 50-ml beakers labeled A, B, C, and D were prepared. 2. Four potato cubes were collected, weighed to the nearest 0.001 g, and their weights were recorded at time = zero. 3. One cube was placed in each beaker. Enough of Unknown Solution A, B, C, or D was added to cover the cube in each corresponding beaker. Potato cubes were removed from their respective beakers at fifteen-minute intervals, blotted to remove excess water, weighed, and the weights were recorded. 4. After the last weighing, the percent weight change from the original weight at each time interval was calculated using the formula: % weight change (t min) = (weight (t min) - weight (0 min)) / weight (0 min) * 100
Ocampo 3 Results: Solution A Solution B Solution C Solution D Time (min) Weight (g) Change (%) Weight (g) Change (%) Weight (g) Change (%) Weight (g) Change (%) 0 2.2 g 0% 1.9 g 0% 1.7 g 0% 3 g 0% 15 2.1 g -4.54% 1.9 g 0% 1.7 g 0% 3 g 0% 30 2 g -9% 2 g 5.3% 1.7 g 0% 2.8 g -6.7% 45 1.9 g -13.6% 2 g 5.3% 1.7 g 0% 2.8 g -6.7% 60 2 g -9% 2.1 g 10.5% 1.7 g 0% 2.7 g -10% 75 1.8 g -1.8% 2.1 g 10.5% 1.7 g 0% 2.7 g -10% When the lab began, I was tasked to use Solution B for my potato, I had a piece of potato, which I weighed to know how heavy it was. It started at 1.9 grams. Then, I put the potato in Solution B.
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Ocampo 4 I checked the potato's weight every 15 minutes. After 75 minutes, the weight went up to 2.1 grams. The results showed that Solution B made the potato get heavier over time. This tells us that Solution B was a hypotonic solution, and it caused the potato to soak up water and gain weight. Discussion: The results indicate that the tonicity of the unknown solutions had a significant impact on the weight change of the potato cubes. As hypothesized, the hypertonic solution (Solution A) caused the potato cube to lose weight over time, with a gradual decrease in weight. The hypotonic solution (Solution B) resulted in the potato cube gaining weight over time, confirming our hypothesis. Water moved into the potato cube into the less concentrated solution, causing it to expand and gain weight. For the isotonic solution (Solution C), the weight of the potato cube remained relatively constant, in line with our hypothesis. Water moved in and out of the potato cube at an equal rate, maintaining its size and weight. Solution D exhibited some minor fluctuations in weight, but the overall trend was relatively going down, indicating that it was a hypertonic environment. Conclusion: This experiment successfully determined the tonicity of four unknown solutions using potato
Ocampo 5 cubes as indicators. The results supported our hypotheses, showing that hypotonic solutions cause weight gain, hypertonic solutions cause weight loss, and isotonic solutions maintain relatively constant weights. This demonstrates the principle of osmosis and its role in biological systems. Citation: Zorin, I. " Osmosis and Diffusion Lab ." Northern Virginia Community College Alexandria Campus, 2023; pgs. 1-10