ACTIVITY 2

ACTIVITY 2

The Wave Bottle

I. Objective:

To create a wave bottle by using liquids of different densities and polarities.

II. Discussion: Mineral oil will not mix with water (because it is nonpolar and water is a polar solvent). It is also less dense than water, and thus will float on top of the water. Food coloring is not soluble in mineral oil, but is readily soluble in water (in fact, it is purchased as a water solution). Careful observation when the food coloring is added to a bottle containing water and mineral oil allows us to "see" the results of the collisions of molecules. The water in the wave bottle consists of many water molecules. The molecules of food coloring spread erratically throughout the water, changing direction when they collide with the water molecules, until they are thoroughly mixed with them. When you perform the experiment, notice also that when falling through the mineral oil, the cohesive forces of the drop of food coloring pull it into a sphere, minimizing its surface area. Vegetable oil can also be used in place of mineral oil, but it is colored and may become rancid. Vegetable oil is a mixture of triacylglycerols obtained from vegetable sources. While not extremely reactive under normal conditions, it will react with oxygen over a period of time to produce some discoloration. . Mineral oil is a mixture of liquid hydrocarbons obtained from petroleum, and is considerably more inert than vegetable oil.

III. Materials: A clear, colorless bottle with a cap, enough mineral oil to half fill the bottle, water, food coloring.

IV. Procedure:
Fill the bottle ½ full of mineral oil. The bottle must be clean and contain no soap residue.
Fill the bottle the rest of the way with water. Observe which liquid ends up on top and which on the bottom.
Observe carefully as you add several drops of food coloring. Start out with only a few drops. If you want a darker solution, you can always add more later.
Put the cap on the bottle and tighten firmly.
Turn the bottle on its side, rock it back and forth, and observe.

V. Questions:
1.Which liquid is less dense and floated on top?
2.Describe what happened when the food coloring was added to the mineral oil.

3.Describe what happened when the food coloring entered the water layer.
4.What other liquids could be used to prepare a wave bottle?

VI. Generalization: