homework lab

NAME:__________________________ SECT:_________

EXPERIMENT #1: DIFFUSION RATE

Data Table for Diffusion of Different Molecular Weights

Methylene blue (molecular weight of 320)

Time 15 min 30 min 45 min 60 min

Distance in mm

Potassium permanganate (molecular weight of 158)

Time 15 min 30 min 45 min 60 min

Distance in mm

1) What are the three things which influence the movement of molecules (and particles)? Circle the variable that was measured in this experiment.

2) Which dye, the methylene blue or the potassium permanganate, diffused at the fastest rate?

3) Why did one dye diffuse faster than the other?

EXPERIMENT #2, PART 1: OSMOSIS

Table of Osmotic Potential and Time

Time Osometer reading *Movement in mm

0 3 -

15 10 7

30

45

60

75

90

*To calculate movement in mm you will need to subtract the preceding value from the succeeding value

1) Over the 90 minute period, what distance did the column of sugar move?

2) Which term is used to describe the tonicity of the distilled water? (Hypotonic or Hypertonic)

3) Explain why the sugar solution rises in the thistle tube over time.

4) Explain why the diffusion rate of water changed over the 90 minute period of time.

5) We began the experiment by pouring a 20% sucrose solution into the thistle tube. Describe what the makeup of the sucrose solution probably is after the 90 minute period. (more or less than 20%).

6) Describe why this change in sucrose % has changed.

7) From the knowledge you have gained could you explain why it is not a good idea to drink salt water when you are thirsty.

EXPERIMENT #2, PART 2: DIALYSIS

TABLE OF DIALYSIS TESTS

Solution Glucose Test Tape (+/-)

Lugol’s Solution (+/-)

Glucose Solution

Starch Solution

Dialysis Tube Solution After Soaking in Distilled Water

Beaker of Distilled Water Before Insertion of Dialysis Tube

Beaker of Distilled Water After Insertion of Dialysis Tube

1) Considering tonicity how would you describe the relative tonicities of the, a) dialysis bag solution, and b) beaker solution?

2) By analyzing the differences between the tonicities of the solutions in the bag and the beaker, where should water diffuse to, a) into the bag, or b) into the beaker?

3) Did starch diffuse from the bag? Why or why not?

4) Did glucose diffuse from the bag? Why or why not?

5) Did osmosis occur during this experiment? Why or why not?

6) Did dialysis occur during this experiment? Why or why not?