Nov. 10, 2004

Hard-Surface Cleaners

Water is undoubtedly the cheapest and most abundant cleaner around. Unfortunately, it is not the most efficient. Although it is called the "universal" solvent because more chemicals dissolve in water than in any other liquid, there is a large class of compounds that simply don't mix at all with water: greases and oils. When dirt adheres to grease that adheres to surfaces, something besides water is called for.

Soaps and detergents are substances that mix with both greases and water. When oil, water, and soap are mixed together, soap molecules become arranged between water and fat molecules, held in a suspension called an emulsion. Although the emulsion is often temporary, it lasts long enough to flush away the grease along with the dirt.

The cleaning solutions sold in hardware stores are called "hard-surface" soaps and detergents, as opposed to the kind of detergents used in washing machines.

Materials and Equipment

• small, slim olive jars with lids, as many as you can collect (Olive jars are a good substitute for test tubes. However, if you have access to test tubes, use them instead.)
• measuring cup
• measuring spoons
• salad oil
• assortment of soap: liquid, soap flakes, detergents, etc.
• assortment of hard-surface cleaners: Fantastik, Mr. Clean, Windex, etc.
• clock
• pencil and paper

Procedure

Put a quarter cup of cold water in each jar. Add one tablespoon of salad oil to each jar. Put the lid on one jar containing oil and water. This will be the "control" in your experiment. (A control has all of the elements of an experiment except for the one you are changing.) Add one tablespoon of soap or hard-surface cleaner to each of the other jars. Label each jar so you know which cleaner you have added. Shake the jar containing oil and water hard about five times. Using the second hand on a clock, see how long it takes to separate into two clear separate layers of oil and water. I found that my sample separated in about forty-five seconds.

Observations and Suggestions

The longer it takes for the oil and water to separate into two layers, the better the emulsifier. The better the emulsion, the more time you have to rinse away dirt. I found that liquid soap was better than hard-surface cleaners. Some brands were faster than others, also. Try powdered cleaners. Dissolve a small amount in water before you add a teaspoon to the oil-water mixture. Do an experiment to see how water temperature affects the emulsification.

Reprinted with permission from The Secret Life of Hardware: A Science Experiment Book by Vicki Cobb. Text © 1982 by Vicki Cobb (www.vickicobb.com). Published by J.B. Lippincott.

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