Polar and Nonpolar Solvents

Introduction

In this activity you will investigate the solubilities of seven solutes in two different solvents -- water (H₂O), a polar solvent; and vegetable oil, a nonpolar solvent.

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1. The contents of the microcentrifuge tubes will be mixed with the 2 solvents. Transfer the solid solute samples on the end of of microspatula or wooden splint.
2. Place 10 drops of water in each of 7 wells in the 12-well strip.
3. Place a few crystals of Urea in well 1; iodine in well 2; ammonium chloride in well 3; naphthalene in well 4; copper(II) sulfate in well 5; and sodium chloride in well 6. Add 5 drops of ethanol to well 7.
4. Gently mix the contents of each well with the end of a tooth pick.
5. Judge the extent to which each solute dissolved in the polar solvent water. Record your observations in the data table using the following key: S = soluble; SS = slightly soluble; IN = insoluble.
6. Discard the contents of the wells, following teacher directions.
7. Add 10 drops of nonpolar vegetable oil in each of 7 wells in the second 12-well strip.
8. Repeat the preceding steps, substituting the vegetable oil for water.

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1. Do polar substances dissolve in polar liquids?
2. Do nonpolar substances dissolve in nonpolar liquids?
3. Do polar substances dissolve nonpolar liquids?
4. Which solutes were more soluble in water than vegetable oil?
5. Which solutes were more soluble in vegetable oil than water?
6. Did any solutes produce unexpected results? If so, describe these results. Can you suggest reasons for this behavior?
7. Explain the phrase, "Like dissolves like."

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Safety

Wear eye protection and an apron at all times. Direct contact of chemicals with the skin should be avoided. Be especially cautious in handling iodine, which can irritate the skin and eyes.

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1. Polar substances tend to be soluble in polar liquids.
2. Nonpolar substances tend to be soluble in nonpolar liquids.
3. Polar substances do not tend to dissolve in nonpolar liquids.
4. Ammonium chloride, copper sulfate, sodium chloride, urea, and ethanol were more soluble in water than in vegetable oil.
5. Iodine was more soluble in vegetable oil than water, but the results were not clear cut.
6. Naphthalene did not dissolve well in either water or vegetable oil.
7. The phrase that "like dissolves like" means that polar substance tend to form solution with one another, and that nonpolar substances tend to form solutions with one another.. Polar and nonpolar substance do not tend to form solutions with one another, however.

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Use very small crystals of solid. The naphthalene does not dissolve well in vegetable oil.

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• The following solvents stored in pipet storage devices:
  • water
  • vegetable oil or mineral oil
• The following solutes stored in microcentrifuge tubes:
  • urea crystals
  • Iodine crystals
  • sodium chloride (NaCl)
  • Ammonium chloride (NH₄Cl)
  • Naphthalene (C₁₀H₈)
  • Copper (II) sulfate (Cu SO₄•5H₂O)
• The following solute stored in a pipet device:
  • Ethanol (C₂H₅OH)
• 2 12-well strips
• wood splints
• tooth picks
• cotton swabs

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The original version of this lesson was developed by:

Terry Wortman
Hayes Center High School
Hayes Center, NE

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