Miscibility and Solubility of Common Household Substances
Introduction:
Miscibility is the property of substances to mix in all proportions, forming a
homogeneous solution. The term is most often used to refer to liquids, but applies also to
solids and gases. Water and ethanol, for example, are miscible because they mixt in all
proportions. By contrast, substances are said to be immiscible if a significant proportion
does not form a solution. [1] Miscibility of two materials is often determined optically.
When two miscible liquids are combined, the resulting liquid is clear. If the mixture is
cloudy, the two materials are immiscible. Care must be taken with this approach as two
materials with similar indices of optical refraction would produce false conclusion on
miscibility. [1]
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to
dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the
solute in the solvent. The solubility of a substance fundamentally depends on the physical
and chemical properties of the solute and solvent as well as on temperature, pressure and
the pH of the solutions. [2] Most often, the solvent is a liquid, which can be a pure
substance or a mixture. The extent of solubility ranges widely, from infinitely soluble
(without limit) (fully miscible) such as ethanol in water, to poorly soluble, such as silver
chloride in water. The term insoluble if often applied to poorly or very poorly soluble
compounds. [2]
A popular aphorism used for predicting miscibility and solubility is “like dissolves like”.
This statement indicates that a solute will dissolve best in a solvent that has a similar
chemical structure to itself. This view is simplistic, but it is a useful rule of thumb. The
overall solvation capacity of a solvent depends primarily on its polarity. For example, a
very polar (hydrophilic) solute such as urea is very soluble in highly polar water, less
soluble in fairly polar methanol, and practically insoluble in non-polar solvent such as
benzene. In contrast, a non-polar solute such as naphthalene is insoluble in water, fairly
soluble in methanol, and highly soluble in non-polar benzene. [2]
Purpose:
The student will investigate and determine the miscibility of common household
substances in water and vegetable oil.
Materials / Equipment:
Table salt
Table salt large crystal
Table sugar powder
Rock candy
Rubbing alcohol (isopropyl alcohol)
Olive oil
Distilled water
Vegetable oil
Kimwipes
400-mL beakers as waste jars
Safety:
 Always wear safety glasses and apron in the chemistry lab.
 Never eat or drink in the chemistry lab.
 Avoid contact of all chemicals with eyes and all body tissues.
 All substances are none hazardous. No need to wear gloves.
Pre-lab Questions:
1. What is water? What is the formula for water? Are water molecules nonpolar,
polar of ionic?
2. What is vegetable oil? What is the best representation of vegetable oil? Are
vegetable oil molecules nonpolar, polar or ionic?
3. What is your hypothesis on miscibility between water and vegetable oil?
4. What is table salt? What is the formula unit for table salt? Is table salt nonpolar,
polar or ionic?
5. What is table sugar? What is the formula for table sugar? Are table sugar
molecules nonpolar, polar or ionic?
6. And what is olive oil? Are olive oil molecules nonpolar, polar or ionic?
7. What are your hypotheses on solubility of table salt and rock candy in water and
vegetable oil, respectively?
Procedure:
Part 1—miscibility in water
1. Take five clean test tubes and put on the test tube rack.
2. Pour distilled water in each test tube to approximately one inch in depth.
3. In the first test tube, carefully introduce ten drops of vegetable oil. Observe.
Shake the test tube well, put it back on the test tube rack and observe.
4. In the second test tube, carefully introduce small amount of table salt. Note: salt
crystals covering the tip of metal specula are sufficient. Observe. Shake the test
tube well, put it back on the test tube rack and observe.
5. In the third test tube, carefully introduce small amount of sugar. Note: sugar
crystals covering the tip of metal specula are sufficient. Observe. Shake the test
tube well, put it back on the test tube rack and observe.
6. In the fourth test tube, carefully introduce ten drops of rubbing alcohol. Observe.
Shake the test tube well, put it back on the test tube rack and observe.
7. In the fifth test tube, carefully introduce ten drops of olive oil. Observe. Shake
the test tube well, put it back on the test tube rack and observe.
Part 2—miscibility in vegetable oil
1. Take five clean test tubes and put on the test tube rack.
2. Pour vegetable oil in each test tube to approximately one inch in depth.
3. In the first test tube, carefully introduce ten drops of water. Observe. Shake the
test tube well, put it back on the test tube rack and observe.
4. In the second test tube, carefully introduce small amount of table salt. Note: salt
crystals covering the tip of metal specula are sufficient. Observe. Shake the test
tube well, put it back on the test tube rack and observe.
5. In the third test tube, carefully introduce small amount of sugar. Note: sugar
crystals covering the tip of metal specula are sufficient. Observe. Shake the test
tube well, put it back on the test tube rack and observe.
6. In the fourth test tube, carefully introduce ten drops of rubbing alcohol. Observe.
Shake the test tube well, put it back on the test tube rack and observe.
7. In the fifth test tube, carefully introduce ten drops of olive oil. Observe. Shake
the test tube well, put it back on the test tube rack and observe.
Part 3—additional miscibility tests
1. Take four clean test tubes and put on the test tube rack.
2. For each test tube, pour distilled water in to approximate two inches in depth.
3. Take two large table salt crystals. Put one aside and one inside a clean mortar.
Use the pestle to smash the large salt crystal into smaller pieces. Finer the
particles the better.
4. Take two large rock candy crystals. Put one aside and one inside a clean mortar.
Use the pestle to smash the large rock candy crystal into smaller pieces. Finer the
particles the better.
5. In the first test tube, put in a large table salt crystal. In the second test tube, put in
the smashed table salt crystals from the mortar. Observe both test tubes
simultaneously. Shake both test tubes, wait for 5 minutes and observe again.
6. In the third test tube, put in a piece of rock candy. In the fourth test tube, put in
the smashed table sugar crystals from the mortar. Observe both test tubes
simultaneously. Shake both test tubes, wait for 5 minutes and observe again.
Post-lab questions:
1. Are the hypotheses proven true or false by the observations?
2. Does “like dissolves like” fit into the conclusion drawn in this lab?
References:
[1] Wikipedia: http://en.wikipedia.org/wiki/Miscibility
[2] Wikipedia: http://en.wikipedia.org/wiki/Solubility