USE FROM REFUSE PROJECT
WAVE IN A BOTTLE

Materials:

Any size clear plastic bottle, water, food coloring (any color), vegetable oil or mineral oil

• Remove any label from the bottle by filling the bottle with hot water from the tap (this should be done by an adult to avoid any danger of children scalding their skin). Swirl the water around - this will melt the label glue. Smaller bottles require less oil and water and work as well as the larger bottles.
  
  
• Fill the bottle half full with water and add a drop or two of food coloring (color of choice). Fill the bottle the rest of the way with vegetable oil or mineral oil (available from the grocery store pharmacy department).
  
  
• Cap the bottle. As you rock the bottle vertically, the wave motion will become apparent. The wave motion is also apparent when the bottle is held horizontally and gently rocked, however, the period of the wave is longer.

Resource Information: There are several lessons which can be taught with this simple device. The objective of making this device is to observe wave motion. There is also the phenomenon of the oil remaining on top of the water. This phenomenon is due to two characteristics of oil: (1) The molecules of the oil are hydrophobic ("water fearing") and (2) oil is less dense than water.

With regard to wave motion, the students can learn that the top of the wave is the crest and the bottom portion is the troughs. One wavelength is the distance between successive crests or trough, as shown in the accompanying diagram of a wave. The wave height is the distance from the top of the crest to the bottom of the trough. The period of the wave is the time it takes for successive crests or troughs to pass a fixed point.