A shampoo with a cream rinse is basically an oil change for your hair. The shampoo takes out the old oil and the cream rinse adds new oil. Shampoos work on the principle that "like dissolves like." They work this way: Shampoos contain large molecules called surfactants such as sodium lauryl sulfate. Surfactants have a polar end and a nonpolar end. The polar end dissolves in water and the nonpolar end dissolves in the oil and grease in your hair. Agitation loosens the oil and grease. Water washes it away.

Shampoos are so efficient that they effectively remove most of the natural oils in your hair, leaving it dry and unmanageable. Cream rinses help replace the natural oils lost in shampooing and make your hair soft and shiny. Thus a shampoo and cream rinse are basically an oil change for your hair.

Let's go to the Infoplease.com Surface Active Agent dictionary entry to learn more about surfactants.

1. What is a surfactant?
   
   
2. List the four major types of surfactants described on the All About Hair site.
   
   
3. Define the four major types of surfactants you listed in Question 2 using the Surfactants, Soaps and Detergents Dictionary.
   
   

Additional Activities

1. You can take an interactive quiz about the unusual properties of water.
   
   
2. You can read the Discover Magazine article entitled "Wet, Wild and Weird" and report on the strange properties of the compound we call water. On the Discover Archives page, enter "Wet" in the title field and click Search.