Description
Name: _________________________
Date: _________________________
Section #: _________________________
Lab 2: Diffusion, Osmosis and Solubility
Purpose (1 point):
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Directions: watch this video: https://www.youtube.com/watch?v=tHzkRtzVmUM
Experiment 1
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Fill a glass with water to within ~2cm of the top.
Add a very small amount of instant coffee.
Measure time it takes to begin dissolving and finally make the whole glass “brown”.
Repeat now with a drop of food die/coloring.
Measure time it takes to begin dissolving and finally make the whole glass “colored”.
1. Was there a difference in time for coffee and food coloring to dissolve? Why? (1 point)
Experiment 2
2. Obtain a Ziplock bag and fill it with lots of table salt and water, but do not fill COMPLETELY the
bag, leave a bit of “space” for water to enter. Add one/two drops of food coloring to the bag.
6. Check if your membrane is leaking by gently squeezing your bags. If there is a leak, you need
to make sure the zip is tight.
1. Poke 5 VERY SMALL holes with a thin sewing needle.
7. Place the Ziplock bag in a bigger container/glass/jar with water.
8. Note the initial volume of liquid in the membrane with a marker. Mark the level of the initial
volume of water in your jar/glass.
9. Allow membrane to sit for ONE HOUR.
1. Why are we using food coloring in the zip solution? What does food coloring test for? (2
points).
2. Results (1 point):
Color inside zip
(before)
Color outside zip
(after)
Volume of zip,
marker (before)
Volume of zip,
marker (after)
3. . Was diffusion, osmosis or both observed in this experiment? (3 points).
Experiment 3:
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Pour half a cup of balsamic vinegar (dark) and half a cup of water inside a glass.
Mix the contents well with a whisker.
Record what you see.
Add half a cup vegetable cooking oil.
Mix the contents well with a whisker.
Record what you see.
Using a teaspoon of your dish detergent. Mix the contents well with a whisker.
Record what you see.
1. Results: In each empty box, record what you see after you have added that reagent (1 point).
Water + Balsamic
Vegetable Oil
Detergent
vinegar
2. What was the purpose of adding the detergent? (1 point).
Post-lab questions:
1. Define polarity (1 point):
2. A membrane that allows certain molecules to pass through but not others is known as what
kind of a membrane? (1 point).
3. You have a membrane that is permeable to potassium ions and water. The membrane is not
permeable to sodium ions. The concentrations are listed below for each molecule on either
side of the membrane. Explain the net movement for EACH molecule (3 points).
Molecule
Outside of the Membrane
Inside of the Membrane
Potassium ions
16M
6M
Sodium Ions
8M
3M
Water
10mL
2mL
Potassium ions:
Sodium ions:
Water:
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