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Diffusion Across A Model Cell Membrane Lab Report

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Grade 7 Diffusion Across a Model Cell Membrane Question: Can iodine or corn starch molecules diffuse across a plastic “membrane?” Hypothesis: If the iodine and cornstarch are placed in the same beaker, then the answer can be determined. Materials: Plastic sandwich bag Zip-lock bag Tincture of iodine Cornstarch (2) 500 mL beakers Eyedropper Graduated cylinder Procedure: Fill one beaker with 250 ml of water Add 60 drops of iodine Fill a second beaker with 250 mL of water Add 3 teaspoons of cornstarch and mix well Pour ½ of the starch and water solution into the plastic sandwich bag Make sure that there is NO spilled solution on the outside of the bag Place the bag in the beaker with the iodine/water solution Immediately observe any changes Observe and record …show more content…

The iodine solution is a yellow, the molecules transported through the plastic bag and to the cornstarch. Day Three The color of the iodine is decreasing the iodine molecules diffused with the cornstarch. The cornstarch is darker and settling at the bottom of the bag, separating it from the water. Day Four Iodine solution is clear, with orange specks, and the cornstarch is a dark lavender. The water inside the plastic bag is a light lavender. The iodine molecules diffused with the cornstarch. The colors have changed/decreased. The molecules went from the iodine, through the plastic bag, to the cornstarch. The light lavender is cloudy and the dark lavender is very thick. Analysis: The chart shows the difference in the iodine/water solution and the plastic bag filled with cornstarch processed over the time span of four days. Conclusion: In conclusion, the molecules went from the iodine, through the plastic bag, to the cornstarch. This lab shows that molecules can transport through a material as thick as a plastic bag. Is the hypothesis correct or incorrect? The hypothesis is correct Why is it

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When starch was mixed with three drops of Lugol’s, it tested positive for starch and the color changed to black. Lugol solution is a starch indicator. This happened because starch on its own can’t break down into sugar, so it stayed as a starch. When distilled water and amylase were mixed together, it tested negative for both, starch and sugar, and the color change for both, the sugar testing changed to blue and the starch test turned to yellow. This happened because in science distilled water is called a control which is not being tested but used for comparison.

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At equilibrium, the small molecules could pass through while the larger ones remained in the bag. The other group mixed starch and iodine in the bag. The initial color observed was dark blue. When I went back the next day, I saw no change; the solution in the dialysis bag was still dark blue and the

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The hypothesis that starch would not diffuse was correct. The orange color of the iodine beaker stayed the same, which supports the hypothesis that starch did not diffuse. If it had diffused, the color would have become black, like the tube. The hypothesis that iodine would diffuse was correct. The color of the tubing turned black after the iodine had diffused, which is an indication that the iodine hypothesis was correct.

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In an effort to showcases how various substances diffuse through membranes, an experiment was performed. Frist, we weighed the mass at the start, to compare it with the weight at the end, and they were expected to gain mass. We left the experiment for a week and left it to diffuse. We then weighed the bags none of them gained mass, which may suggest a random (water stuck in the knot) or systematic (scales) error. We then tested for the substances outside of the tubing

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After 8 minutes the three cubes were removed and we measured the distance the vinegar diffused. We then calculated the percent of the cube which vinegar entered for each cube. As observed from our results, the size of the cubes did not change the rate at which vinegar diffused. The rate of diffusion was the same for all cube sizes. The distance the vinegar diffused was the same for all cubes because the rate of diffusion was not affected by the size of the agar cubes.

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