Ingredients: water, cyclohexane, microwave oven

Procedure: A complete recipe follows.

1. Place bottles with small quantities of water and cyclohexane in microwave oven. "Cook" for a bit.

2. Remove bottles and have objective observer test temperatures by hand.

3. Substantial differences in temperature are noted - the water is quite hot while the cyclohexane remains near room temperature - which can be checked quantitatively with a thermometer.

Understanding: Through our common experience, we grow up knowing that "oil and water don't mix." When we think of "oil," we can think of hydrocarbon chains like hexane, C₆H₁₄, and octane, C₈H₁₈. We can also think of hydrocarbon rings like benzene, C₆H₆, and cyclohexane, C₆H₁₂. When we think of "water," we think of ... water, H₂O.

The differences observed in the behavior of hydrocarbons and water can be understood using the concept of electronegativity. We think of alkali metals being very electropositive, holding their outermost valence electron loosely. So loosely they often give it up. The most electropositive end of the Periodic Table is found near cesium. We think of halogens as being very electronegative, holding their outermost valence electrons tightly. And they want more. The most electronegative corner of the Periodic Table is found near fluorine.

In cyclohexane, the difference in the electronegativity of the hydrogen and the carbon is not great. As such, in the "battle for electrons" waged by the atoms, it is a "draw." The carbon and hydrogen atoms enter the relationship neutral, and remain relatively neutral after forming covalent bonds that define the structure of the cyclohexane molecule. That makes cyclohexane nonpolar.

In water, the difference in electronegativity of the hydrogen and oxygen is great. Oxygen is able to draw the electrons in the covalent bonds away from the hydrogen nuclei. As a result, the oxygen-hydrogen bonds have a polar character, with the oxygen end being negatively charged and the hydrogen end being positively charged. Overall, the bent water molecule has a substantial dipolar character, and water is a very polar liquid.

The electromagnetic waves of a microwave oven interact strongly with molecules with dipoles. The energy in the electromagnetic microwaves can be absorbed by polar molecules, making them move more vigorously and increasing the temperature of the liquid. In our experiment, the polar water is heated substantially, while the nonpolar cyclohexane is left relatively uneffected - a dramatic demonstration of the great difference in polarity of the two liquids.