Chemical & Physical Reactions in
Cleaning
Review

Cleaners are concerned about
pH

pH describes the number of H+
ions in a solution

A difference of 1 whole number
in pH represent a 10-fold
increase.

Cleaners expect certain types of
products to fall into a specific
range of pH.
Further Review

Some information cleaners have
received about pH is inaccurate
or misleading.

There is more to chemical
strength or reactivity than pH.

Most cleaning is accomplished
by physical reaction not
chemical reaction.
What is a Chemical Reaction?

Molecules of one kind are changed
to molecules of something different.

An acid rust remover does not
remove rust, but changes it to
something different that is colorless.

Oxidation and reduction are
chemical reactions.
Do you remember these terms from an earlier class?
Physical Changes

Most carpet cleaning involves
physical changes.

An example of a physical change
is dissolving salt in water. The salt
and water are combined but they
did not change into anything
different. When the water
evaporates, the salt is still salt.
Physical Changes

Water soluble soils are
removed by dissolving them
in water and extracting the
water.

Oily soils are removed by
dissolving them in solvents.
Mixtures

A mixture is another type of
physical change.

An example would be combining
salt and sugar. They mix, but the
salt is still salt and the sugar is still
sugar.

No chemical reaction takes place.
Neither is dissolved by the other.
Nothing new is formed.
Mixtures

Water and oil do not normally
mix, they separate when
combined.

With the addition of an
emulsifier, the oil can form
small droplets that disperse
and mix in water.

Salad dressing is an example
of water and oils mixing.
Physical Reactions

Most carpet cleaning is
done by the physical
reactions of dissolving or
emulsifying and then
extracting.

pH plays only a small role
in a physical reaction.
The Role of pH

Most soils are acidic,
between 4 and 5.

Things can be
dissolved faster when
neutralized so,
alkaline cleaning
agents help speed
this process.
pH and Chemical Reactions

Highly alkaline agents can
combine with oily molecules to
form soap. This is called
saponification.

An example is lye soap. Highly
alkaline lye was combined with
animal fat to make soap.

A highly alkaline product such
as Prolon can combine with
oils or grease in the carpet to
form a basic soap that rinses
out of the carpet easier than
the oil and grease.

Chemical reactions can
change the soils we are
trying to remove.

Chemical reactions can
also produce changes
in the fibers or dyes we
are cleaning.

Using physical
reactions to clean is
safer than using a
chemical reaction.
Other Factors That Contribute
to Chemical Reactions
In addition to pH, other
factors that influence
chemical reactions include:
•Reactivity
•Total Alkalinity
•Buffering
Lets see what each of these terms means
and what effect they can have on
cleaning.
Reactivity

Nitrogen and oxygen are two
gases in our atmosphere.

Nitrogen seldom reacts with
anything.

Oxygen is quick to react. It
combines with iron to form rust.
Oxygen oxidizes oils to form a
difficult to remove stain.
Anything burning is combining
with oxygen.
Reactivity – What’s the point?
Some things react more readily
than others. This must be
considered along with pH to know
how severe a reaction will occur.

An example: The pH of a common
cola beverage is similar to the pH of
an acid tile and grout cleaner.

The chemical reactions if you
ingest them are very different.

Buffering

The pH of some solutions changes quickly
when mixed with another solution or from
being “used up” reacting with soils.

The pH of other solutions remains very
stable even when water is added or soils
are present.

The ability to keep a stable pH is due to
buffering.

Buffering is the addition of additional
“reserve” alkalinity.
Total Alkalinity

A solution that with plenty of
“reserve” alkalinity and an
unbuffered solution may both
have the same pH.

Which one do you think has
higher “Total Alkalinity?”
Total Alkalinity

A solution with low total
alkalinity can “run out” of
ions and slow down or
stop a reaction.

A solution with high total
alkalinity can sustain a
chemical reaction.
Is buffering a “Good” thing?

It depends.

When cleaning wool, a buffered
cleaning agent with high total
alkalinity can damage the wool
and/or the dyes because even a
slight residue left behind will not be
neutralized but will remain highly
alkaline.

For cleaning oil and grease, a
buffered solution helps maintain
pH for greater saponification.
The Big Picture
A cleaning agents role in
producing a chemical
reaction depends upon
several factors –



pH
How reactive the chemical is
Total alkalinity
Summary

Thorough cleaning is
accomplished mostly by products
that produce physical reactions
such as dissolving, emulsifying
and lubricating.

Slight chemical reactions may
happen with many cleaning
chemicals.

Most chemical reactions are
caused by specialty agents such
as bleaches (reducers &
oxidizers), rust removers and
similar.