Acids and Bases as Cleaners
Name: Kayla H.
After completing a lab that I created, in which I
compared a basic acid cleaner, vinegar, to a basic base cleaner, laundry
detergent, I noticed that the acid cleaner cleaned metal better and the
base cleaner cleaned stains on cloth better. Why is this, and I no the
laundry detergent cleaned the cloth better because it is laundry
detergent, but why was the acid cleaner unable to do the same?
The acidic vinegar dissolved oxidation and corrosion on the metal thus
giving the appearance of "cleaning" the metal. It would not have been so
effective at removing greasy dirt from the metal. The detergent has a
molecular structure that is has a hydrophobic tail and a hydrophilic head.
These molecules form aggregates called micelles in which the hydrophobic
tails are buried inside the micelle and the hydrophilic head is oriented
toward the water. Oily dirt migrates into the micelles and is held in
suspension. stabilized by the hydrophilic shell.
Your lab experiment sounds intriguing. Clearly you were able to
demonstrate two different types of cleaning which can occur.
For many metals, and you do not specify what you used, much of the
dullness comes from the creation of an oxide layer on the surface. This
coating actually helps the metal resist chemical attack to some degree.
By cleaning with an acid, you were able to react with and dissolve this
coating making the metal shiny again.
On cloth, most stains like dirt, etc. are non-polar. Laundry detergent
is made up of non-polar surfactants which help to dissolve the stain and
make it soluble in water. As you may remember from chemistry, like
dissolves like. The detergent was better suited for handling non polar
In general, cleaning effects can be divided into two categories: (1)
solubility, and (2) chemical reaction. When cleansers act to aid or speed up
the dissolution of dirt into water, then the cleanser is acting like a
bridge between the solvent - water, and the dirt. When the cleanser is
acting like a chemical reactant, then the cleaning action is done by
reacting with the dirt and changing the chemical composition of the dirt
into something that is more soluble in water.
So now you need to look into how the acid in vinegar might act on metals or
the particular "dirt" that is on metals, and how this might be different
from the way a base-derived cleanser would act on the same "dirt.
Greg (Roberto Gregorius)
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Update: June 2012