Tuesday, October 5, 2010

Scribe Post 10/5/10 Diffusion Lab and Quiz


First we talked about the naked egg experiment, in which an egg is placed in various substances to prove the diffusion that takes place while the egg is in the substances.

Next we set up for the lab.

Then we took a quiz and when we were finished recorded our results from the lab.

Lab Summary:

The lab was about diffusion, and was a cellophane dialysis tube with starch, water, and glucose, sitting in a beaker of iodine and water. When the tube was observed after the quiz the water had turned almost black inside the tube and the beaker seemed to have stayed the same. The color change was because of the combination of iodine and starch within the tube. The iodine got in the tube because of diffusion and because it started with a higher concentration in the beaker and moved to lower concentration in the tube.

Lab Questions:

You know the iodine diffused in the lab because of the color change in the tube, showing the presence of iodine and starch.

The starch however did not diffuse to the outside of the tube, because if it had, the water in the beaker outside the tube would have been black like the inside of the tube, because the iodine and starch would have mixed. It didn't diffuse because it was a lower concentration than the occupants of beaker around the tube.

The glucose didn't obviously diffuse during the lab, or the water would have been a bit darker in the beaker because glucose and iodine turn dark brown when mixed.

Iodine and water diffused through the membrane of the cellophane tube.

Starch and glucose did not, that we could observe, diffuse through the cellophane tube membrane.

The failure of starch to diffuse through the membrane could have been because the molecules were bigger and less concentrated and didn't need to diffuse to an area of lower concentration to be spread out.

Materials can't pass through selectively permeable membranes going different directions at the same time, because it's selectively permeable and only certain amounts of certain substances can pass through at once.

The materials that diffused in opposite directions during this experiment were water and iodine.

A cell is dead when it is in complete equilibrium with its surroundings because nothing is being transferred. No energy or materials are being passed back and forth therefore the cell isn't functioning and would be dead.

It's harmful to add salt water to a fresh water plant because the salt soaks up the water that the plant needs to absorb, and the plant becomes dehydrated.

Next scribe Christine K.

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