KanCRN | Out, darn spot! | Guided Research | Background
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   Out, darn spot! Guided Research: Background     
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In the "What do we already know?" Section, we share the information that we already know about our area of research. This is also known as the Background Information section.

Believe it or not soap was developed not for cleaning but for dying wool.  Wool, when it comes from sheep, has a layer of grease (called lanolin) that interferes with the application of dyes.

Things changed with the invention of  Lye soap. Washing the wool in Lye soap removed the lanolin allowing  the wool to be dyed.
How does soap work? 
Soap was first made from boiling beef fat (called tallow) with ashes. That's right like ashes you get from burning wood. The mixture made the molecules in soap have a unique property. The longest part of a soap molecule called the tail  repels water (It acts like it hates water and this is called hydrophobic).
At the same time a special part at the head of the molecules attracts water. (It acts like it loves water and this is called hydrophilic.)
The reason soap molecules are good for cleaning is that oily things like to stick together...just like oil molecules like to stick together in a bottle of salad dressing.

Why do we need to use soap?

Most soils we come in contact with are water soluble which means water and the motion of the washing machine are enough to clean clothes.  If clothes are extra dirty, the dirt may settle back on the clothes instead of going down the drain. Detergents (or soaps) are needed because they use chemicals that keep the dirt floating in the water so that it does not go back on the clothes.
When you wash greasy, dirty clothes, water alone cannot remove the soil.
Adding soap or detergent to the water makes the water soak deeper into the clothing.
The tails of soap molecule not only hate water, but they love dirt. They work their way between the dirt and the clothes.
The soap molecules surround the dirt and keep it from getting back on the clothes.

Do detergents get rid of every spot on the clothes?
Sometimes we get spots or stains on our clothes that will not dissolve in just water. In this case, you have to use other things that might break down the spot so that it can be carried away in the wash water. Different spots are made up of different things. A variety of products may be used to get rid of the spot. You have to decide which one.
Substances that have the same characteristics of the spot (they have a similar chemical formula) will be the best for breaking up the spot. Salt and water have the same characteristics so salt will break up in water...
but, salt and oil are not similar so they will not mix.
In the same way, motor oil will not mix with water...
but it will mix with gasoline.
 
To successfully remove a spot, you are going to have to find solvent that is similar to the stain, but won't remove the color of the clothes.

A good researcher will look at other information, more than what you find here. You probably want to find out more about soap, solvents and methods using books, encyclopedias, magazines, websites or other resources. We invite you to share any new information you discover.

Click on a link to read the information that others have found or type in new information below.



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    After you have read and understood the information above and you feel you've found enough information on the topic, you are ready to plan how you're going to find out which solvents and methods will be best for removing the mustard and Kool-Aid stains. Go to the What we're going to do Section now.

  2003, Pathfinder Science