Lab 4 Diffusion and Osmosis Essay

Custom Student Mr. Teacher ENG 1001-04 17 April 2016

Lab 4 Diffusion and Osmosis

1. Diffusion and Osmosis, June 4, 2013

2. Purpose: The purpose of this lab is to help give visual understanding of diffusion which is a solution of high concentration spontaneously (no energy required) moving to an area of low concentration. Also taking a look at osmosis, which is the movement of chemicals across the cell membrane. Osmosis requires some type of energy to be put in for this to happen. After these experiments we should have a better idea and visualization of how chemicals transfer across the cell membrane.

3. Materials:

Dropper bottle of water
Compound microscope
Dissecting needle
Carmine powder
Slide and coverslip
3 test tubes
Transfer pipets
2 400 ml beaker
30 cm moist dialysis tubing
500ml beaker
Hot plate
Benedicts reagent
I2KI solution starch solution
Wax pencil
30% glucose solution
String or rubber band
Test tube rack
Slides and cover plates

4. Methods and Procedures:
Experiment 1:
Prepare a slide of dry carmine and water and cover slip Put under the microscope, examine under the different magnifications, record you findings to later set up your conclusion. Experiment 2: Use dialysis tubing that has been soaking in water, fold it “accordion style” and use string to close the ends like a bag. Roll opposite end of bag till it opens and add 4 pipettes of 30% glucose into it. Add 4 pipettes of starch solution into it.

Mix contents with bag closed. Then rinse with tap water. Add 300 mL of water to a 400- to 500- ml. add a few drops of solution till it turns an amber-yellow color. Leave bag in beaker for 30 minutes.
Remove bag then let it dry.
Record observations.

Experiment 3:
Obtain 7 equal size bore hole cylinder from the potato, cut roughly to the same size record the length and weight of each making sure they remain order. Next is to collect 7 cups filled with 100 ml of the 6 different concentrations of glucose (, 0.1 0.2, 0.3, 0.4, 0.5, 0.6, and water). Record the time and submerge the potato cylinders in the solutions. Let them sit for an hour and half before removing, weighting and recording the final weight.

5. Observations and data:

Experiment 1:
Carmine powder observation: movement is random, looks like continuous vibrations Experiment 2:
Table 1
Benedicts Test

Test final color
Before heat of Benedicts test
After heat Final Color
Water (control)
Baby blue
Slight yellow
Baby blue
Yellowish green
Baby blue

After letting the bag sit inside the bath for 30 minutes the solution inside the bag went from a clear color to a slight yellow color. And after the final results of benedicts test I can conclude the carbohydrates did move from inside the bag out.

My observation concerning the size of the potato cylinder in the glucose decreased as the concentration of glucose increased and the potato in water remained the same size. 6. Conclusion:

The carmine powder experiment proved the theory of diffusion because with no energy required you can see the movement of particles under a microscope. Again diffusion is the movement of molecules from high concentration to low concentration with no energy required. On the other hand the experiment concerning osmosis were the dialysis bag and the saturation of the potato. Both experiments demonstrated the movement of sugar or water across a cell membrane. On the dialysis bag experiment we could see the slight color change as the IKI did move across the membrane in to the bag but the big surprise was see that after the benedicts test how strong the sugar content was in the beaker solution.

Lastly the potato experiment demonstrated through the change in weight how water could pass through the membrane. As we saw the greater concentration of glucose the more shriveled the potato got, indicating the water inside the potato exited out trying to make the concentration equal. The solution containing strictly water made the potato swell as if the concentration inside was lower than the concentration outside.

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  • University/College: University of Chicago

  • Type of paper: Thesis/Dissertation Chapter

  • Date: 17 April 2016

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