Diffusion, Osmosis and Solubility

Name: _________________________

Date: _________________________

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Section #: _________________________

Lab 2: Diffusion, Osmosis and Solubility

Purpose (1 point): _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Directions: watch this video: https://www.youtube.com/watch?v=tHzkRtzVmUM

Experiment 1

  1. Fill a glass with water to within ~2cm of the top.
  2. Add a very small amount of instant coffee.
  3. Measure time it takes to begin dissolving and finally make the whole glass “brown”.
  4. Repeat now with a drop of food die/coloring.
  5. 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

 

  1. 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.
  1. 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.
  2. Place the Ziplock bag in a bigger container/glass/jar with water.
  3. 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.
  4. 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).

 

 

 

 

 

 

 

  1. Results (1 point):
Color inside zip

(before)

Color outside zip

(after)

Volume of zip, marker (before) Volume of zip, marker (after)
       

 

  1. . Was diffusion, osmosis or both observed in this experiment? (3 points).

 

 

 

 

Experiment 3:

  1. Pour half a cup of balsamic vinegar (dark) and half a cup of water inside a glass.
  2. Mix the contents well with a whisker.
  3. Record what you see.
  4. Add half a cup vegetable cooking oil.
  5. Mix the contents well with a whisker.
  6. Record what you see.
  7. Using a teaspoon of your dish detergent. Mix the contents well with a whisker.
  8. Record what you see.

 

  1. Results: In each empty box, record what you see after you have added that reagent (1 point).
Water + Balsamic vinegar Vegetable Oil Detergent
     

 

  1. What was the purpose of adding the detergent? (1 point).

 

 

 

 

Post-lab questions:

  1. Define polarity (1 point):

 

 

 

 

 

 

  1. A membrane that allows certain molecules to pass through but not others is known as what kind of a membrane? (1 point).

 

 

 

 

  1. 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: