# Perform a first-hand investigation to carry out saponification and test the product

Procedure:

Saponification:

1. Place 5g of NaOH pellets in a 100mL
1. Using a Bunsen burner, bring the solution to a boil, taking care to stir constantly so as to provide a uniform
2. Allow the solution to cool once the layer of oil has fully
1. Add 10g of NaCl and bring the solution once more to a boil, again taking care to stir
1. Allow the solution to cool, at which point lumps of soap should
1. Decant the solution taking care to keep the
1. Flush the beaker with a NaCl solution 2-3 more times, decanting after each successive
1. Allow the soap to dry in the fume cupboard, upon filter

Testing:

1. Take six test tubes, filling two with the soap, two with synthetic commercial detergent, and leaving the remaining two
2. Fill all six test tubes halfway with water, and a third as much of
1. Stopper all six test tubes, and shake each one vigorously, taking care to keep the contents within the test
2. Record your observations for each test tube five, ten, and fifteen minutes after shaking. In particular, note whether or not the liquids have formed an emulsion or separate layers, and the height of foam each

Expected results:

• The soap and detergent observations are likely to show varying amounts of foam depending upon the length of shaking and the detergent used, as well as the purity of the However, in general, you will find that the detergent produces the most foam.
• The soap and detergent observations result in an emulsion of water and oil, whereas the test tube of simply water and oil is likely to seemingly form an emulsion at first, but settle into separate layers relatively quickly

# Describe saponification as the conversion in basic solution of fats and oils to glycerol and salts of fatty acids

Saponification is the hydrolysis of an ester in an alkaline environment, where fat or oil is combined with hydroxide ions to form an alcohol and a carboxylate ion (COO−).

Remember- In particular, saponification is the process of converting fats and oils in sodium hydroxide into glycerol (Propane-1,2,3-triol) and the salts of fatty acids.

# Gather, process and present information from secondary sources to identify a range of fats and oils used for soap-making

This dotpoint is best served by learning around there different oils and two different fats.

Oils:

• Avocado Oil- Primarily used in
• Castor Oil- Produces a soap which is relatively
• Olive Oil- Produces a durable and hard

Fats:

• Lard- Derived from pig fat and produces a mild soap which is used for
• Tallow- Derived from the solid fat of beef cattle and produces soap which is yellow in

# Describe the conditions under which saponification can be performed in the school laboratory and compare these with industrial preparation of soap

In the school laboratory, esters are boiled in a solution of sodium hydroxide to produce a homogenous mixture. Given the volatility of the substances being handled- in particular the ester- this process must take place in reflux. Given that alkanoic acids have higher melting and boiling points than their alkanol counterparts- a characteristic attributable to the stronger dispersion forces of a longer carbon chain- several options are then possible:

• If the carboxylate ion has more than four carbon atoms, its solubility is likely to be relatively As such, it may be precipitated out in its acidic form upon being acidified, and then filtered off.
• If the carboxylate ion has an extremely low degree of solubility, it may simply be removed upon being cooled with
• If the carboxylate ion has a boiling point which is relatively different, distillation may be used to separate the

The key characteristics of this process are:

• A water bath and hotplate are
• The full reaction can be brought about within an
• Refluxing is
• The product is relatively impure, with quantities of sodium hydroxide
• Process is dependent upon different boiling and melting points.

In the industrial preparation of soap, vegetable oils and fats are heated to high temperatures in a 30% sodium hydroxide solution. The product has all surface fat skimmed upon cooling, and the remaining mixture is mixed with brine. By increasing the concentration of ions present in the mixture, the soap is precipitated out in a process known quite simply as ‘salting out’. Colouring and perfumes are then combined with the product which is then packaged by being cut and pressed into a mold. The brine solution is combined with acid to neutralise any excess sodium hydroxide, and then distilled to produce the glycerol.

The key characteristics of this process are:

• Significantly higher temperatures are
• Although the process may be completed in a day, the reactions can take several days, if not weeks to go to
• The fat and/or oil are not as volatile, resulting in no need for refluxing.
• Any remaining sodium hydroxide can be neutralised and the remaining water distilled, leaving a relatively pure
• Process is dependant upon the ‘salting out’

# Perform a first-hand investigation to gather information and describe the properties of a named emulsion and relate these properties to its uses

Many different emulsions can be found in everyday situations. For the sake of simplicity, this study guide will simply describe the emulsion of French dressing.

French dressing is a common salad dressing generally containing vinaigrette among other ingredients. When combined with small amounts of mustard powder and shaken vigorously, a fairly basic emulsion is formed.

French dressing can be described as a water-oil emulsion which is fairly evenly dispersed. When coupled with commercial emulsifiers, this mixture can remain as an emulsion for extended periods of time, resisting any attempt to separate into two immiscible layers.

# Perform a first-hand investigation to demonstrate the effect of soap as an emulsifier

For your ease, this study guide uses the same procedure for both this dotpoint, and for the testing component. The steps are repeated again for your convenience.

Procedure:

1. Take six test tubes, filling two with soap, two with synthetic commercial detergent, and leaving the remaining two
2. Fill all six test tubes halfway with water, and a third as much of
3. Stopper all six test tubes, and shake each one vigorously, taking care to keep the contents within the test
4. Record your observations for each test tube five, ten, and fifteen minutes after shaking. In particular, note whether or not the liquids have formed an emulsion or separate layers, and the height of foam each

Expected results:

• The soap and detergent observations are likely to show varying amounts of foam depending upon the length of shaking and the detergent used, as well as the purity of the However, in general, you will find that the detergent produces the most foam.
• The soap and detergent observations result in an emulsion of water and oil, whereas the test tube of simply water and oil is likely to seemingly form an emulsion at first, but settle into separate layers relatively quickly

# Account for the cleaning action of soap by describing its structure

Soap is an effective surfactant, or surface active agent, due to its unique tadpole-like structure which allows for a two-pronged cleaning effect. The anionic ‘head’ is described as hydrophilic, or water-loving, whilst the hydrocarbon ‘tail’ is said to be hydrophobic, or water-fearing.

By working together, soap is able to act as a bridge in carrying off particles as the ‘tail’ attaches itself to oil and the anionic ‘head’ dissolves in the water. By effectively encircling these oil particles, the particle now carries a negative charge, and as such is unable to resettle on the surface as the particles repel one another.

Particles that are not oily can still be removed as the hydrophilic ‘head’ dissolves in the water and the hydrophobic ‘tail’ sticks up into the air, thereby breaking surface tension. This effectively allows particles to become more wet, and thus wash off.

Remember- The anionic head and hydrophobic tail work together to remove both oily and non-oily particles. This is done by circling and making the oily particle negatively charged, as well as by lowering the surface tension of the water.

# Explain that soap, water and oil together form an emulsion with the soap acting as an emulsifier

An emulsion can be defined as a dispersion of one liquid in another in the form of droplets. While oil and water are immiscible- that is, they do not mix when combined- when soap is added they form an emulsion as the oil breaks up into small droplets within the water. This occurs as the hydrophobic ‘tails’ of soap particles attach themselves to oil particles and the hydrophilic anionic ‘heads’ of soap particles dissolve in water, bridging the oil particle and the water, and dispersing the oil particles throughout the mixture.

Remember- An emulsifier is a substance that produces an emulsion from two or more otherwise im- miscible solutions. Soap acts as an emulsifier between oil and water due to its tadpole-like structure.

# Distinguish between anionic, cationic and non-ionic synthetic detergents in terms of: Chemical composition, and uses

Anionic detergents have a structure similar to that of soap, with a long hydrocarbon tail and an anionic, sulfonate ‘head’ ($OSO_2O$). These surfactants are generally more effective as cleaning agents than soap, and as such are used in dishwashing detergents as well as laundry detergents. Generally, anionic detergents produce a degree of foam. However, this foam has no impact- both beneficial and detrimental- upon the performance of the synthetic detergent.

Cationic surfactants are derivatives of the ammonium ion in which the hydrogen atoms are replaced by alkyl groups. These surfactants can be formed by two long alkyl group chains in between ten and twenty carbon atoms in length, and two to three methyl groups with a charged nitrogen ‘head’. Cationic detergents are particularly useful in the cleaning of fabrics, textiles, and even hair, as they are absorbed into the material, reducing friction and static charges. Another use includes both domestic and commercial cleaning agents for plastic, as well as antiseptics and biocides.

Non-ionic detergents similarly have a long hydrocarbon tail, but the opposite end is a long polar oxygen component ending in an alcohol group. The presence of the ethoxy groups (CH2CH2O) helps in producing this polarity when combined with the hydrogen end. Non-ionic detergents find much use in cosmetics, paints and adhesives, as they tend to produce far less foam than their anionic counterparts.

# Distinguish between soaps and synthetic detergents in terms of: The structure of the molecule, chemical composition, and its effect in hard water

The Structure of the Molecule

Soaps may be distinguished from synthetic detergents by way of their molecular structure, as where soaps have a hydrocarbon tail and an ionic or polar ‘head’ which is usually anionic, synthetic deter- gents, despite having a similar structure, can have an anionic, cationic or non-ionic ‘head’.

Chemical Composition

Where soaps are made of metal (usually sodium or potassium) salts of long alkanoic fatty acid chains, synthetic detergents consist of hydrocarbons and either a sulfanate end (anionic), nitrogen end (cationic), or ethoxy group end (non-anionic).

Effect in Hard Water

Hard water is simply water high in calcium and/or magnesium cations. When soap comes into contact with hard water, it creates ‘scum’, a greyish precipitate which limits the cleaning ability of the soap.

In contrast, synthetic detergents do not form precipitates with hard water, with cationic and non- ionic surfactants experiencing no effect at all. However, although synthetic detergents do not react with hard water, anionic surfactants may form soluble complexes with the calcium and magnesium cations, effectively neutralising the anionic surfactant and limiting the cleaning potential of the synthetic detergent.

# Solve problems and use available evidence to discuss, using examples, the environmental impacts of the use of soaps and detergents

Early detergents were branched anionic alkylbenzene sulfonates chains which had poor biodegrad- ability, causing excessive foaming in our waterways. Newer detergents have solved this issue, but have brought new concerns as well.

In order to combat hard water, detergents often contain ‘builders’ such as sodium tripolyphosphate (Na5P3O10). These work to reduce the hardness of water while simultaneously increasing pH to the optimum level at which the surfactant operates. However, phosphates are a key reagent in the eutrophication of our waterways, an as such, the discharge of detergents has lead to high algal bloom rates causing the death of marine ecosystems.

Cationic synthetic detergents have also proved problematic as they act as biocides, causing much damage if the runoff continues to a sewage treatment plant, as these plants rely upon bacteria to decompose the sewerage- bacteria which are effectively killed off.

In contrast, soaps have had very little impact upon the environment, as they readily break down into the harmless components of carbon dioxide and water.