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9.2
2.i
Lifestyle Chemistry – Section 2 ::: Study Sheet
Perform a first-hand investigation to prepare an emulsion and compare its properties to
those of a solution and suspension
Compared mixtures – Water + [coppersulphate], [olive oil, detergent], [olive oil], ……
Use a blender, or stir vigorously, to mix the following pairs of chemicals.
Then, observe for the following homogeneous/non-homogeneous; clear/cloudy; check for
Tyndall effect, leave to stand overnight – settles out or form layers
Results
Suspensions – light scattered from all mixture; layers appear quickly
Emulsions – appear white; exhibit Tyndall effect; particles remain separated
Solutions – appear clear; no scattering of light; no layers
Practical skills - see 9.1
2a
State the relationship between the properties of an emulsion and the types of molecules
present???
Oil-in-water emulsion Oil molecules (droplets) spread thru water
Water-in-oil emulsion Water molecules (droplets) spread thru oil
Different particles result in different properties
O/W conduct; feel cool; mix with water; dissolves water-soluble dyes (methyl orange)
W/O poor conductor; feel greasy; mix with kerosene; dissolve oil soluble dyes (Sudan III)
2ii
Plan … a first-hand investigation to gather information about the properties of different
emulsions and use available evidence to compare those properties
Different types of emulsions - O/W and W/O emulsions [Test several]
Tested for conductivity; feel; mix with kero/water; solubility of dyes
Difficulties – some tests required experience; eg difficult to tell if dye dissolved or just coloured
emulsion; If no conductivity was equipment working – needed to check
Reliability – repeat test at least three times for each emulsion to check consistency of results
Validity – Variables controlled to allow comparison: same tests, same
2b
Outline the purpose of the emulsifying agent in a range of consumer cleaning products
The purpose of the surfactants in cleaning products is to break up greasy oil based compounds
into small droplets. Then the emulsifying agent helps to thoroughly disperse the droplets and
then keep the droplets separated.
2c
2d
Identify that soaps and detergents are emulsifying agents and surfactants
Explain why cleaning agents must be surfactants and emulsifiers
Cleaning agents must be surfactants and emulsifying agents because they need to be able to
carry out three functions
Cause
Surfactants reduce surface tension
Effect
Which allows the cleaning agent to penetrate the
material more completely (wetting agent)
Surfactants attach to the soil, then the water Which results in the soil being lifted off the
molecules pull on the surfactant molecules, which material
then pull on the soil
The heads of the surfactant molecule molecules Which causes the soil particles to remain
repel each other
separated and suspended
2e
Define the term biodegradable
The biodegradability of a chemical is its capacity to be broken down by the biological action of
living organisms. The end result is the complex chemical is converted into simple molecules of
carbon dioxide, water and salts.
2f
Discuss the biodegradability of soaps and soap less detergents
Introduction
Define biodegradability; Soap is a type of detergent made from animal fats and
alkalis; Synthetic detergents made from chemicals found in petroleum.
Issue 1 Soaps
Soaps are biodegradable; that is,
they are quickly broken down by
bacteria, and thus do not pollute
rivers.
Soaps have a number of problems when compared to
detergents. When used in hard water a sticky precipitate forms,
which settles on the material being cleaned. Another residue
remains on the material because soap does not completely rinse
out.
Soaps do not have the cleaning power of modern synthetic
surfactants.
Issue 2 Detergents
Early detergents were not completely
biodegradable.
They sometimes
produced large amounts of foam in
rivers and streams that received
sewerage effluent.
Many modern detergents use compounds containing
phosphate. This chemical is a fertilizer for plants and
causes problems such as blue-green algae outbreaks and
eutrophication. So, even though modern detergents are
biodegradable, they can still cause problems to the
environment.
Modern detergents biodegradable – ie
break down to simple molecules
Scientists are continuing to develop detergents where the
biodegradable products do not cause environmental
problems. Today, while phosphates are still used in
detergents, it is possible to buy and use phosphate-free
detergents.
2
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