K11 Chemistry ISB: Soaps: Chemistry Cloze Answer (at the end of this document)
To understand what is needed to achieve effective cleaning, it is helpful to have a basic
knowledge of soap and detergent chemistry.
Water, the liquid commonly used for cleaning, has a property called
1_______________ _______________. In the body of the water, each
molecule is 2_____________ and 3_______________ by other water
molecules. However, at the 4________________, those molecules are surrounded by
other water molecules only on the water side. A 5________________ is created as the
water molecules at the surface are pulled into the body of the water. This tension causes
water to bead up on surfaces (glass, fabric), which slows 6________________ of the
surface and inhibits the cleaning process. You can see surface tension at work by placing a
drop of water onto a counter top. The drop will hold its shape and will not spread.
In the cleaning process, surface tension must be 7_____________ so water
can spread and wet surfaces. Chemicals that are able to do this effectively are
called surface active agents, or 8_______________. They are said to make
water "wetter."
9________________ perform other important functions in cleaning,
such as 10________________, 11________________ (dispersing in
water) and holding soil in 12_______________ until it can be rinsed
away. 13_______________ can also provide alkalinity, which is useful in
removing acidic soils.
Surfactants are classified by their 14_______________ (electrical charge) properties in
water: 15_______________ (negative charge), 16_______________ (no charge),
17_______________ (positive charge) and 18_______________ (either positive or
negative charge).
Soap is an 19_______________ surfactant. Now let's look closer at the chemistry of
surfactants.
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K11 Chemistry ISB: Soaps: Chemistry Cloze Answer (at the end of this document)
Soaps
Soaps are water-soluble 20_______________ or 21_______________ salts of
22_____________ _____________. Soaps are made from 23_______________ and
24_______________, or their fatty acids, by treating them chemically with a strong
25_______________.
First let's examine the composition of fats, oils and alkalis; then we'll review the soap
making process.
Fats and Oils
The fats and oils used in soap making come from animal or plant sources. Each fat or oil is
made up of a distinctive mixture of several different 26_________________.
In a 27_______________ molecule, 28_______________ fatty acid molecules are
attached to one molecule of 29_______________. There are many types of
30_________________; each type consists of its own particular combination of fatty
acids.
Fatty acids are the components of fats and oils that are used in making soap. They are
31_______________ acids composed of two parts:
A 32________________ acid group consisting of one 33_______________ atom, two
34_______________ atoms, and one 35_______________ atom, plus a
36_________________ chain attached to the 37_______________ acid group. Generally,
it is made up of a long straight chain of carbon (C) atoms each carrying two hydrogen (H)
atoms.
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K11 Chemistry ISB: Soaps: Chemistry Cloze Answer (at the end of this document)
Alkali
An alkali is a 38_______________ salt of an alkali metal like sodium or potassium.
Originally, the alkalis used in soap making were obtained from the 39_______________ of
plants, but they are now made commercially. Today, the term alkali describes a substance
that chemically is a 40_______________ (the opposite of an acid) and that reacts with
and neutralizes an acid.
The common alkalis used in soapmaking are 41_______________ _______________
(42_______________), also called 43_______________ _______________; and
44_______________ _______________ (KOH), also called 45_______________
_______________.
How Soaps are Made
46___________________ of fats and oils is the most widely used soapmaking process.
This method involves 47_______________ fats and oils and reacting them with a liquid
alkali to produce soap and water (neat soap) plus 48________________.
The other major soap making process is the 49_________________ of fatty acids with an
alkali. Fats and oils are 50________________ (split) with a high-pressure steam to yield
crude fatty acids and glycerine. The fatty acids are then purified by 51_______________
and neutralized with an alkali to produce soap and water (neat soap).
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K11 Chemistry ISB: Soaps: Chemistry Cloze Answer (at the end of this document)
When the alkali is sodium hydroxide, a sodium soap is formed. Sodium soaps are "hard"
soaps. When the alkali is potassium hydroxide, a potassium soap is formed. Potassium
soaps are softer and are found in some 52_______________ _______________ soaps
and 53_______________ _______________.
The 54_______________ end of the soap molecule is attracted to water. It is called the
55________________ (water-loving) end. The hydrocarbon
chain is attracted to oil and grease and repelled by water. It is
known as the 56_________________ (water-hating) end.
How Water Hardness Affects Cleaning Action
Although soap is a good cleaning agent, its effectiveness is reduced
when used in 56________________ ________________. Hardness in
water is caused by the presence of mineral salts - mostly those of
57_____________ and 58__________________ (Mg), but sometimes
also iron (Fe) and 59__________________ (Mn). The mineral salts
react with soap to form an 60________________ precipitate known as
soap film or scum.
Soap film does not rinse away easily. It tends to remain behind and produces visible
deposits on clothing and makes fabrics feel stiff. It also attaches to the insides of bathtubs,
sinks and washing machines.
Some soap is used up by reacting with hard water minerals to form the film. This reduces
the amount of soap available for cleaning. Even when clothes are washed in soft water,
some hardness minerals are introduced by the soil on clothes. Soap molecules are not very
versatile and cannot be adapted to today's variety of fibers, washing temperatures and
water conditions.
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K11 Chemistry ISB: Soaps: Chemistry Cloze Answer (at the end of this document)
1 surface tension
2 surrounded
3 attracted
4 surface
5 tension
6 wetting
7 reduced
8 9 13 surfactants
10 loosening
11 emulsifying
12 suspension
14 ionic
15 19 anionic
16 non-ionic
17 cationic
18 amphoteric
20 sodium
21 potassium
22 fatty acids
23 fats
24 oils
25 alkali
26 27 30 triglycerides
28 three
29 glycerine
31 weak
32 37 carboxylic
33 hydrogen
34 oxygen
35 carbon
36 hydrocarbon
38 soluble
39 ashes
40 base
41 sodium hydroxide
42 NaOH
43 caustic soda
44 potassium hydroxide
45 caustic potash
46 Saponification
47 heating
48 glycerine
49 neutralisation
50 hydrolysed
51 distillation
52 liquid hand
53 shaving creams
54 carboxylate
55 hydrophilic
56 hydrophobic
57 hard water
58 calcium
59 magnesium
60 manganese
61 insoluble
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