Diffusion on a Liquid in a Liquid

Part A: Diffusion on a liquid in a liquid.

I did an experiment with three different glasses of tap water from the faucet. All three cups measured the same which happened to be 13 cm from the top of the cup to the bottom of the cup. I let the water settle, and sit for about an hour so the temperature was the same for all three cups. I then placed one drop of food coloring into the first glass and waited for the coloring to reach the bottom. I calculated 93 seconds. I then went to the second glass and duplicated the experiment in the same exact manner and counted 107 seconds. Finally I went to third glass, did the same as before and counted for 103 seconds. To figure the rate of diffusion you must divide the distance the dye migrated in cm by the time it took in seconds. For the first glass 13cm/93sec or 0.14 cm/sec, the second glass would be 13cm/107sec or 0.12 cm/sec, and the third glass would be 13cm/103sec. or 0.13 cm/sec. The average diffusion rate among all three glasses would be 0.13 cm/sec. I do hypothesize that the color of the dye would make a difference in this experiment being that dyes may have a thicker consistency depending on what was used in order to make that color, causing it to be denser than that of a simpler color. Also I do hypothesize that temperature has a lot to do with the rate of diffusion being that heat tends to let molecules move more freely. I hypothesis that the results of this experiment do not vary because of the experimenters mood, but perhaps how the experiment was handled, maybe the drop was put in light on one try and then a more forceful drop the following. I do hypothesis a different outcome in the experiment if the water was moving around opposed to sitting still.

Part B: The Effect of Salt Concentration on Osmosis in Potato Cells.

Introduction:

1. The purpose of doing this lab was to recognize the effects that salt, in different strengths, has on cells.

2. Osmosis is the movement of water molecules across a semi permeable membrane. What occurs is the water travels from a higher area of concentration to area of lesser concentration. In this lab the concentration we are talking about is sodium. With different solutions, there are different effects that occur with cells. There are hypertonic (higher concentration than that of itself), hypotonic solution (lesser concentration than that of itself, and isotonic solution (the same concentration than that of itself).

3. I hypothesize that if cells were in an environment with an isotonic solution that there wouldn't be a change in the appearance, or size of the cells. I hypothesize that in a hypertonic environment the cell would decrease in size being the solution has less concentration than that of the solution. In a hypotonic solution I hypothesize that cells would become enlarged because the solution is of lesser concentration than the cells therefore moving the water into the cell. With the 7% solution I hypothesis the potato will shrink in size. The 3.50% salt solution, I hypothesize, will probably be considered an isotonic solution meaning no change will take place. With the 1.75% salt solution, this I hypothesize will be a hypotonic solution causing the cells to enlarge. And with the 0.00% solution, I think that because of the distilled water, the potato cells will be stripped of some of the nutrients and I think the cells will be smaller in size.

Method:

1. The lab experiment was two take eight slices of a potato measuring exactly in size, 10mm x 10mm x 40 mm in all the core of the potato measuring 4,000 cubic millimeters. Two of each of the cores were placed into four different solutions over a period of 15 hours. A solution of distilled water, a 1.75% salt solution, a 3.5% salt solution, and a 7% s salt solution. All eight pieces then were extracted from the solution, dried off with a paper towel and then remeasured each of the pieces and averaged the size between the pairs and compared them to that of the slices before they were put into the solution.

Results:

1. I found that the specimens placed in the 7% solution were dramatically smaller in size, the texture was a lot softer than before the experiment began and the specimen had become dark in color. It appeared to be shriveled throughout the whole specimen. It measured 2,000 cubic millimeters in size. The specimen in the 3.50% solution was also softer more so on the outside, it appeared to be darkened more towards to outer edges and also smaller in size than the original size pre exposure to the solution. It measured 3,000 cubic millimeters in size. The specimen took from the 1.75% solution seems pretty close to the size that it originally appeared. The color was the same as before however it did seem softer to the touch. It measured 4,000 cubic millimeters in size. The final specimen taken from the 0.00% solution was significantly bigger than before it was placed in the solution and a lot harder. The color stayed the same. It measured 6,000 cubic millimeters in size.

2..

Table 1: Potato Core Measurements