Polar vs. Non-polar Lab

Chemistry

 

Objective:

Part I: Determine the polarity of some common substances.

Part II: Use the polarity of water to separate “inks”.

 

Pre-lab Questions:

  1. What is the chemical definition of polar?
  2. Draw a molecule and label the positive and negative sides.
  3. In what type of solvent will a polar solute dissolve?  In what type of solvent will a nonpolar solute dissolve?

 

Materials: water and paint thinner in small vials, 3 Q-tips, 1 Crayon, 1 washable marker, 1 permanent marker, 1 piece of filter paper, 250-mL beaker

 

Part I: “Like Dissolves Like”

Procedure:

  1. Using a pencil, copy the data table below onto a sheet of paper; draw your table about the same size as the one below.
  2. In your data table:
    1. Using a Crayon, color in the two squares in the Crayon column that are also in the “testing” rows (the squares with the squiggly border).
    2. Using a washable marker, color in the two squares in the washable marker column that are also in the “testing” rows (the squares with the squiggly border).
    3. Repeat the coloring using a permanent marker.
  3. Dip a Q-tip in water and then rub it over the first square.  Record your observations in the “observation” square below.

4.      Use another Q-tip (or the opposite end) and repeat for the other two “water testing” squares; record observations in the squares below.

  1. Dip another Q-tip (or the opposite end) into paint thinner and then rub it over the first “paint thinner testing” square. Repeat the procedure for the final two squares.

Solvent

Crayon

Washable Marker

Permanent Marker

Water testing

 

 

 

Water observations

 

 

 

Paint thinner testing

 

 

 

Paint thinner observations

 

 

 

 

Data:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Part II: Paper Chromatography

 

Background


Chromatography is a method used to separate substances in a mixture.  It is based upon the differences in the polarity of solutes dissolved in a particular solvent.

 


Procedure: 

1.      Obtain a piece of chromatography paper and fold it into eighths.

2.      Using the washable marker, draw a ring (4-cm in diameter) around the center.  (That’s 2-cm from the center.)

3.      Fill the beaker 1-cm high with tap water.

4.      Place the chromatography paper in the beaker so that the center is in the water, touching the bottom; ensure that the ring you have drawn is above the water.  It works to well to reverse some of the folds you have created, and make the paper into a “+” shape with the center (tip) down.

5.      Observe what happens when the water is absorbed up the paper.  When the waterline is about 0.5 cm from the edge of the paper, carefully remove the paper from the water and set it on the desk to dry.

 

Post-Lab Questions: Answer the following in complete sentences.

  1. A Crayon is a (polar / non-polar) substance because…
  2. Washable marker “ink” is a (polar / non-polar) substance because…
  3. Permanent marker “ink” is…because…
  4. Suggest 2 other common substances to test with water and paint thinner to determine their polarity.  Based on your knowledge of these substances, predict their polarity.
  5. Explain, in terms of the properties of water:
    1. Why water moved up the filter paper,
    2. Why washable marker “ink” moved up the filter paper with the water, and
    3. Why some ink colors moved different distances than others.
  6. Based on your results from Part I, how could the chromatography experiment be adapted for use with a permanent marker?