grams. The initial mass of Bag C, was 16. 9 grams. After 15 minutes, the mass increased to 18.8 grams with a change in mass from initial mass of 2.0 grams. After another 15 minutes, the total mass of bag C was 19.3 grams, with a change in mass of 0.5 gram. After weighing it after another 15 minutes, the total mass was finally 21.5 grams, with a change in mass of 1.5 grams. Finally, bag D had an initial mass of 17.6 grams, and after 15 minutes it increased by 1.2 grams, to 18.8 grams. Also, then after another 15 minutes, its total mass was 18.3 grams, with a change in weight of -0.5 g. After 45 minutes, together, the total mass was then 20.8 grams, with a change in mass from previous mass of 2.5 g. Figure 3: Change in Mass of Dialysis Bags. Throughout 45 minutes, the mass of bags A-D, were recorded. The change in masses of the bags throughout time, is shown in the graph above.
Running Head: EXERCISE 9 - DIFFUSION AND OSMOSIS Figure 4: Plasmolysis of an Elodea leaf. Shown above the cytoplasm is no longer pressed against the cell wall. As NaCl was added to the slide with the Elodea leaf, looking through a microscope, the cytoplasm was no longer present against the cell wall. Discussion With the first procedure when observing diffusion across a semipermeable membrane, as the dialysis bag with phenolphthalein was added, the solution outside and the inside of the bag turned pink. Phenolphthalein is a pH indicator that will turn red in a basic solution, so with that means that NaOH had diffused across the dialysis bag, and turned it pink. This shows that NaOH is a strong base. The phenolphthalein molecules had also moved across the semipermeable membrane and turned the outside solution pink also. An error that might have occurred was there might have been a leak in the bag somewhere that allowed the phenolphthalein molecules to go out of the bag and into the solution. The phenolphthalein molecules are too large to pass through the dialysis membrane. With the dialysis bag with the starch solution was submerged into the solution with iodine, the edges of the bag started turning dark blue/ black. Only the iodine solution was able to
Running Head: EXERCISE 9 - DIFFUSION AND OSMOSIS
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- Spring '14
- Osmosis, Semipermeable membrane, bag