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Diffusion Lab Report

Diffusion Lab

Purpose: To find out how diffusion works by using an artificial semi-permeable cell membrane.

Hypothesis: If I use an artificial semi-permeable membrane (dialysis tubing), then I will be able to see how diffusion occurs.

Materials: Dialysis Tubing

Starch Solution

Water

String

250 mL Beaker

Iodine

 

Procedures: 1. Soak a strip of dialysis tubing until the strip becomes soft and opens up on both sides.

2. Then, twist the tubing (approximately 3cm from the end) and tie a piece of string around it.

3. After that, fill the tubing with water and check for leaks.

4. If it’s okay, add two drops of iodine to the water.

5. Then, twist the tubing once more, and tie a piece of string around it.

6. Now, clean up the outside with a paper towel.

7. Next, fill a beaker with 200 mL of starch solution.

8. Place the artificial membrane (dialysis tubing with iodine solution) into the beaker filled with starch solution.

9. Draw what your experiment looks like (Before).

10. Wait 24 hours and record what your experiment looks like (After).

 

Observations: Here are my drawings for the view of the artificial membrane before and after:

 

 

 

Conclusions: I learned from this lab that diffusion occurs when molecules tend to move from an area of higher concentration to an area of lower concentration. The starch solution molecules moved into the dialysis tubing, where it is a lower concentration. The artificial semi-permeable membrane showed how water couldn’t leak out, but the starch solution can enter the tubing because it is so small. When the starch solution entered the dialysis tubing, I saw how diffusion occurs by the fact that the starch solution’s concentration (amount of a substance in a given volume) was higher than the iodine solution so the molecules went to the area with lower concentration, which was inside the dialysis tubing.

Answers to Questions:

Q #1: What role is the dialysis tubing playing?

A: The dialysis tubing resembles a cell’s cell membrane.

Q #2: What happened to the starch solution?

A: The starch solution diffused through the dialysis tubing creating the dark blue color.

Q #3: What happened in the iodine solution?

A: Since the starch solution diffused through the dialysis tubing, the reaction was a dark bluish color.

Q #4: What can you conclude about these reactions in the dialysis tubing and beaker?

A: That the starch solution diffused into the dialysis tubing, moving from an area of higher concentration to an area of lower concentration inside the dialysis tubing.

Q #5: What can you conclude about the size of molecules and membranes?

A: That the size of molecules and membranes are very small for the starch solution to pass through the tubing, even though water couldn’t get out.

 

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