Membranes: Cell Membrane and Purple Dark

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Cell Membranes and Transport
Hands-On Labs, Inc. Version 42-0033-00-01
Lab Report Assistant This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor. Exercise 1: Diffusion

Observations
Data Table 1: Rate of diffusion in different temperatures| | ºC| Minutes|
Temperature| InitialTemp.| InitialColor| 5| 10| 15| 20| 25| 30| 60| Cold| 3| white| white| white| white| white| white| white| Mostly white some blue| Ambient| 25| white| blueish| Light blue purple| blue purple| blue purple| purple| purple| Dark purple| Hot| 96| white| purple| DARKpurpleple| Dark purple| Dark purple| Dark purple| Dark purple| Dark purple|

Questions

A. Write a one-paragraph analysis of the results for the procedure. Provide reasons for the difference in the rate of diffusion at the different temperatures.

The results of this lab were greatly influenced by the temperature of the KI solution. The bag placed in the heated solution began to change color (from white to light purple) almost immediately and changed to dark purple within 7minutes. The second bag in room temp. solution took about 5 minutes to see a slight change in color (from white to light blue) and about 20 to turn dark purple. The third bag in the cold temp. solution barely changed color at all at the end of the hour (bluish tint.) According to the text (p.68), “ Because the driving force for diffusion is the kinetic energy of the molecules themselves. The speed of diffusion is influenced by molecular size ( the smaller, the faster) and by temperature ( the warmer, the faster).” Through this lab experiment we were able to see that diffusion did happen faster in the warm water by seeing the fastest change in color of the contents inside the baggie.

B. Did the sizes of the molecules affect their movement?
Yes, the smaller the molecules (KI) were able to permeate thru the bag where as the bigger molecules (water) and corn start could not permeate thru the membrane bag due to their large size.

C. Give an example of diffusion between: a solid and a liquid; a gas and a liquid; between two different solids.

(solid/solid) Gold and lead- over time, molecules of lead will diffuse into the gold and vice versa.
(solid/liquid) Sugar and water- Sugar will dissolve in water.
(Gas/liquid)Perfume and air- the scent will spread.

Exercise 2: Osmosis
Observations

DataTable 2: Potato Mass|
Contents in TestTube| Initial Mass of Two Potato Strips| Final Mass of Two Strips| MassDifference| % Change inMass| Class Average Percent Change in Mass (if available)| a) Distilled Water| 3.6g| 5g| 1.4| 38%| |

b) 1.0 M Sucrose| 3.4g| 2.1g| -1.3| -38%| |
c) 0.8 M Sucrose| 3.6g| 2.1g| -1.5| 42%| |
d) 0.6 M Sucrose| 3.5g| 2.6g| -.9| -25%| |
e) 0.4 M Sucrose| 3.5g| 3g| -.5| -14%| |
f) 0.2 M Sucrose| 3.4g| 3.7g| .3| 9%| |

Questions
A. Describe how the potato cylinders changed in their turgidity. Identify which of the solutions were isotonic, hypertonic, and hypotonic in relation to the potato.

a) Distilled Water| No change in turgidity. Hypotonic solution.| b) 1.0 M Sucrose| Very turgid. Hypertonic solution.|
c) 0.8 M Sucrose| Turgid. Hypertonic solution.|
d) 0.6 M Sucrose| Moderately turgid. Hypertonic...
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