Why does soap clean?
"The water does not clean, it cleans the soap".100% Coconut Oil Soap Bar | All Natural Organic Pure Cold-Pressed | Softens & Nourishes Dry Skin | 3oz per bar (3 Pack)
- I heard this phrase thousands of times to my grandfather, who taught me very hard to wash my hands properly, especially every time I went home after having been playing for hours in the square of my neighborhood.
- To understand why a compound has certain properties you must first know what it is made of.
- Here comes the Chemistry part, but do not be scared, you can happily skip the italics:
- How do we know what is soluble in what, what dissolves what, and therefore, what is clean to what?
- We go to the popular chemical saying: "Like dissolves like" And when one substance is similar to another? With this phrase we refer to the polarity : the polar substances are only soluble in the polar, and the apolar in the apolar. For example, oil, as you know, can not be mixed in water, and this is because water is polar and oil is apolar. This is the reason why water can not clean fatty residues, because they are not soluble in it, so you can not "drag" them.
- The great thing about soap is that it has a polar part ( hydrophilic , with an affinity for water) and another apolar ( hydrophobic ) which makes it soluble in water as well as in a fat or oil.
- Without using organic formulas, we can draw the soap molecule in the following way, where the circle represents the hydrophilic part (akin to water), and the tail represents the hydrophobic part (akin to fat).
- When we use soap, it has its hydrophobic part towards the fat, and its hydrophilic part towards the water, so that the soap molecules "encapsulate" the fat, and the part outside of that "capsule" is related to water, so it can "drag" and clean!
- When you wash your hands, remember that the grandparents are always right: "The water does not clean, it cleans the soap," and now you know why.
- If you want to synthesize soap you can download the script of the laboratory practice in " El rincón del alumno ".