Discussion
In order to make a justified recommendation on the removal of
stains the following variables were tested in the experiment: temperature,
concentration, agitation, the presence of enzymes in the detergent and the
saturation time. Research was undertaken before the initiation of the
experiment so a justified hypothesis could be made in relation to these
variables. The results obtained from the experiment both supported and opposed
parts of the hypothesis (as seen above). Aside from several anomalies within
the data, with further research the results from the experiment can be
explained using knowledge of detergents, rates of reaction and understanding
the factors that affect these.
In the experiment it was necessary to use laundry detergents
to remove a turmeric stain. Understanding the way detergents work to remove
stains is important when considering the most effective and efficient solution.
Detergents work to emulsify compounds that are not usually soluble in water
(stains) by surrounding the stain molecules and making it easier for water to
detach them from the fabric due to reduced surface tension.
The surface tension of water, the property that allows it to
resist an external force, will limit the cleaning ability. Surface tension is
the net inward force on the surface of water that causes the molecules on the
surface to contract and resist being stretched or broken and is the result of
these molecules being strongly attracted to the molecules below them (Woodrow
Wilson Foundation, 2010). A diagram of this can be seen in Appendix 6. By
lowering the surface tension of water so that it more readily soaks into pores
and soiled areas the effectiveness and efficiency of the water in cleaning the
cloth will increase.
The reason detergents increase the cleaning ability of water
is a result of their ability to decrease the surface tension and therefore
increase the effectiveness of the wash. The main characteristic of detergents
is that their molecules (surfactant) consist of hydrophilic ends and
hydrophobic ends (Clark, 2009) .
The detergent (surfactant) molecule has
a non-polar (hydrocarbon) and an ionic (polar) head (Appendix 2). The polar
head is attracted to water because of the net dipole of a water molecule. In
water, oxygen attracts electrons with greater strength than hydrogen resulting
in a net dipole (Appendix 3 and 4). The attraction between the hydrophilic end
of a surfactant in a detergent and the water molecule will considerably weaken
the forces between the water molecules and decrease the surface tension. As
well as the ability to decrease surface tension of water, the hydrophobic ends
of surfactants attaches to fats and oils often seen in stains. So, the
detergent molecules (surfactants) attach themselves to the dirt particles of
the stained material and these particles are pulled out and suspended,
surrounded by water, until they are rinsed away (Appendix 5).
This reaction between the stain, detergent and water is
affected by numerous factors. Within this experiment results were obtained relating
to the effect of temperature, agitation, enzymes, concentration and saturation
time. These variables were chosen as the preliminary research suggested that
they would affect the rate of reaction (excluding saturation time).
The highest rate of reaction would allow the greatest amount
of stain to be removed from the material because the greater the rate of
reaction the greater the amount of stain removed in a specific amount of time.
When two or more chemicals react particles must collide with the correct
orientation and enough force to yield a successful reaction (activation
energy). Increasing the rate of reaction relies on the increase in the
likelihood of successful collisions. Since a chemical reaction between
detergent, water and stain particles will only occur with the collision of
these particles in the correct orientation, increasing the number of these
collisions will increase the reaction rate.
Temperature
To determine the effect of temperature on the cleaning
process the cloth was tested in a cold wash, warm wash and hot wash. In order
to obtain fair and accurate results while testing the temperature, it was ensured
that the variables water, detergent, concentration of detergent, agitation and
time were controlled.
For this section of the experiment it was hypothesised that
if the temperature was increased then the rate of reaction would also increase
resulting in a cleaner product. The results obtained from the experiment
clearly showed that this was the effect temperature had on the cleaning of the
cloth. The results revealed that 100% of the hot wash tests obtained better
results than the corresponding cold and warm washes. The warm wash also
achieved a better result than the cold wash in every test. The hot wash
achieved a better result than the warm wash by an average of about 5 points on
the colour scale (colour scale located in Appendix 1). This is clearly shown in
the graphs located in Appendix 9. Each line noticeably shows a relationship
between an increase in temperature and an increase in the cleanliness of the
cloth. In fact, the 4 best results (23) obtained in the entire experiment
involved a hot wash (70 degrees Celsius) and 15 out of the 16 best results also
involved a hot wash (see Appendix 8). The table in Appendix 10 shows that every
cloth achieved a higher rating of cleanliness in the warm wash than the cold
wash and that every cloth in a hot wash achieved a higher rating than in the
warm wash independent of the other variables. From these results and the
assumption that the test was fair, it is possible to conclude that the
hypothesis is fully supported by the results.
The effect that temperature has on this experiment and the
results obtained can be explained in relation to the effect that the increase
in temperature has on the rate of reaction. When a substance is heated the
particles move faster as the heat energy is transferred to kinetic energy. The
increased temperature, and therefore increased kinetic energy, makes the
molecules accelerate and move around more; so, there is more chance of a
collision between molecules. In addition, the molecules will impart a greater
amount of energy in collision due to the gain in kinetic energy and therefore
increase the chance of achieving the activation energy needed in order to have
a successful collision. On the contrary, if the reaction occurs at a lower
temperature there is a lower chance of the molecules colliding due to decreased
speed and energy of particles.
It is obvious that the results were obtained because of the
change in temperature. However, it is also possible to see that there is a
difference in the cold washes, warm washes and hot washes between tests. This
indicates that other variables can also affect the rate of reaction and the
cleaning process.
Enzymes
To determine the effect that the presence of enzymes in
detergent has on the cleaning ability two different laundry powders were used.
The first, Woolworths Home Brand, did not contain enzymes and the second, Fab
Laundry Detergent, did. This was observed on the packaging on both of the
detergents. It was ensured that between tests only one variable was changed
(the detergent) to maintain accurate results.
It was hypothesised that if the laundry detergent contains
enzymes then the rate of reaction will increase. This hypothesis was supported
by about 72% of the tests with the laundry detergent containing enzymes
obtaining an average of about 3 shades lighter than that of the cloth washed
with the laundry detergent with no enzymes. The difference between the
detergent with no enzymes and the detergent with enzymes is greatest when the
cloth is washed in the cold washes and the 10 minute saturations. While most of
the time the enzyme laundry detergent produced better results, a number of
unexpected results can also be seen through the data. It was hypothesised that
enzymes would produce better results than no enzymes regardless of the
controlled variables. However in 3 tests, the detergent with no enzymes yielded
worse results than the same test with a detergent containing enzymes by between
1 and 3 shades. These anomalies (seen in Appendix 7) occurred in the [Cold Wash, Concentration 2,
No Agitation, 30 minutes] test, the [Warm Wash, Concentration 1, Agitation, 10
minutes] test and the [Hot Wash, Concentration 2, No Agitation, 10 minutes]. As
these tests have nothing in common it is not possible to make a conclusion
about the determining factor and may have been cause by an error. Another 7
tests produced the same shade of colour in the resulting cloth. In the [Cold
Wash, Concentration 1, No Agitation, 30 minutes], [Warm Wash, Concentration 1,
Agitation, 20 minutes], [Warm Wash, Concentration 1, Agitation, 30 minutes], [Warm
Wash, Concentration 1, No Agitation, 30 minutes], [Warm Wash, Concentration 2,
No Agitation, 30 minutes], [Hot Wash, Concentration 2, No Agitation, 20 minutes]
and [Hot Wash, Concentration 2, No Agitation, 30 minutes] tests, the presence
of enzyme had no influence on the final product (seen in Appendix 11).
Enzymes
will normally increase the rate of reaction and improve the cleaning process
because of the characteristic that allows them to lower the activation energy
of a chemical reaction and decrease the reaction time. By lowering the
activation energy each collision between particles and subsequent reaction
requires less energy to be successful. The three dimensional shape of an enzyme
brings reactant closer together into its active site, therefore allowing the
chemical bonds to weaken and change with less energy. An enzyme acts as a biological catalyst,
increasing the rate of the reaction without changing the molecule and without
raising the temperature. As the reaction requires less energy to occur the
particles are more likely to have successful collisions. This explains why the
enzyme detergent had more influence (raising the resultant shade by an average
of 3 points) on cold and (raising the resultant shade by an average of 2.5
points) warm washes when compared to the influence it had on the hot washes
(raising the resultant shade by an average of 1.5 points). The hot washes have
adequate energy to overcome the activation energy without the use of enzymes
because of the additional heat energy. Using enzymes in the cooler washes had
more effect because the reduced energy was able to be used more efficiently in
the reactions as a result of the enzymes.
Concentration
To determine the effect that the concentration of detergent
has on the cleaning ability two different concentrations of powders were
tested. The first, 1.25g, was taken from the recommended usage for the Fab
Laundry Detergent and scaled down to fit the amount of water being used
(100mL). The second concentration used was double the first amount to create a
significant difference and with the anticipation that the results would vary
greatly. It was ensured that between tests only one variable was changed (the
detergent) to maintain accurate results.
It was hypothesised that if the concentration of laundry
detergent was increased then the rate of reaction would increase and the
tablecloth would be cleaned more effectively. The results revealed that this
was not the case 66% of the time. In fact in 24/36 tests, concentration 1 (the
smaller amount of laundry detergent) proved to result in a cleaner cloth (see Appendix
12). 6/8 of the best results obtained (colour 22 and 23) used concentration
one. While there were 4 tests conducted that supported the hypothesis, the
majority went against it. Where the hypothesis was supported and concentration
2 obtained a better result the difference between was minimal, only 1 or 2
shades. An anomaly in this data, where concentration 2 achieved a better result
by more than 3 shades if colour was the result from the [No Enzyme, Cold Wash,
Agitation, 20 Minutes] test.
Although the results from the experiment were unexpected they
can be explained using relevant theory. It was expected that the increase in
the concentration of laundry detergent would result in a crowding of the
particles and therefore an increase the likelihood of particles colliding (see Appendix
7). However, in the experiments conducted it seemed as though the amount of
water and stained cloth limited the amount of detergent that was used in the
reaction. It was observed that when the 2nd concentration was used
in tests the water was cloudy at the end of the saturation time. This may be
due to an excess amount of detergent being used and the water acting as a
limiting reagent in the reaction. This limiting reagent will stop the reaction
when it is completely consumed and there is nothing the excess reactant can
continue to react with. So, increasing the concentration will only increase the
reaction rate while there is a ratio where each reactant can be used
completely.
Agitation
To determine the effect of agitation on the cleaning process
the tests were conducted controlling the other variables and saturating the cloth
in either an agitated beaker (with magnetic stirrer) or a beaker with no
agitation. In order to obtain fair and accurate results while testing the effect
of agitation, it was ensured that the variables water, detergent, concentration
of detergent, temperature and time were controlled.
For this section of the experiment it was hypothesised that
if agitation was present then the rate of reaction would increase and the cloth
would become cleaner. The hypothesis was supported by about 55% of the results
(20/36) where agitation provided a better result; however, agitation did not
affect 16% results and the cloth without agitation achieved a better result 25%
of the time (see Appendix 9). The results suggest that agitation had a greater
influence on the cold and warm washes than the hot washes. This trend is seen
when comparing the percentage of cold and warm wash tests with agitation that
achieved better results than the tests without agitation with the percentage of
hot wash tests with agitation that achieved better results than the tests
without agitation. About 62% of cold and warm wash tests were improved by the
use of agitation compared to only about 40% of hot wash tests improved by
agitation (see Appendix 13). While 5 out
of 8 of the best results (22 and 23) were obtained with the use of agitation,
the worst 3 results (4 and 5) were also obtained with the use of enzymes (see Appendix
8). These results strongly suggest that agitation only affects the result
slightly compared to some of the other variables.
The effect agitation has on the rate of reaction and
subsequent cleaning of the cloth is related to the increase in the likelihood
of collision. Agitation keeps reactant particles in motion increasing the
chance of collision in the correct orientation (AUS-e-TUTE, 2013). The stirring also increases the
kinetic energy of the particles and therefore increases the chance of the activation
energy being obtained in a reaction. However, where the other variables are
together decreasing the rate of reaction the presence of agitation does not
have as much of an influence over the result and will not be able to change the
outcome.
Time
To determine the effect of the saturation time on the
cleaning process the tests were conducted over 10, 20 and 30 minutes. 3 pieces
of material were in each beaker and 1 was removed after 10 minutes, another was
removed after 20 minutes and the third was removed after 30 minutes so that the
environment and variables were controlled.
It was hypothesised that if the time was increased then the
resulting fabric would be cleaner. The results supported the hypothesis to some
extent. Overall, the 20 and 30 minutes washes outperformed the 10 minute wash
almost 100% of the time. However, when comparing the results from the 20 and 30
minute tests the improvement is not as obvious if there is an improvement at
all. In fact, the 30 minute wash only obtained the best results in 12 out of 36
tests, obtaining the same result as the 20 minutes wash in 7 tests and the 20
minute wash obtaining the better result in 3 tests (see Appendix 14). 3 of the
4 tests that achieved the highest result (23) were saturated for a total of 30
minutes (see Appendix 8).
The longer the material is left in the water the cleaner it
should become. This should occur because the reaction has the greatest amount
of time to take place and therefore particles should collide more in 30 minutes
than with the same variables in 10 and 20 minutes. A factor that may have
affected these results quite dramatically and could explain the discrepancy
between the practical and theoretical components is the colour of the original
material before being placed in the beaker. While every piece of material was
stained by turmeric, each cloth had a varying degree. If a single piece of
cloth was stained to a lesser degree than another it could take less time to remove
the stain.
Errors
A number of errors were made during the experiment that may
have affected the accuracy and validity of the results. As mentioned above, the
original degree of stain in each individual piece of cloth was not considered
or observed. The resulting colour of the material may have been improved
relative to another piece of material because the original stain was not as
bad. Another mistake that was made during the experiment was that the surface areas
of each detergent were not considered. Prior research (available in log book)
has made it known that surface area will affect rate of reaction and therefore
the cleaning process. So while the detergents had similar surface areas the
effect of the difference cannot be shown. As well as this it was assumed that
the Home Brand laundry detergent had no enzymes. As it wasn’t listed on the
product packaging it was assumed that like most home brand detergents it did
not contain enzymes (according to prior research) but it is a possibility that
there were some form of enzymes present. In the experiment for temperature it
was found that maintaining the temperature on a hot plate was extremely
difficult. Often the temperature of the water became too high because the hot
plate would continue to heat the water past the required temperature. If not
monitored very closely, the temperature could not be kept completely consistent
throughout the entire saturation time.
Improvements
Improvements could have been made to this investigation in
order to be an accurate representation of a washing technique. The use of an
actual washing machine and a full size table cloth would have improved the
validity of the experiment and provided results relevant to the task. The
experiment may also have been improved by increasing the accuracy of measurements,
controlling the environment, controlling the surface area of each detergent and
observing the initial staining of each individual piece of cloth. Using a wider
variety of concentrations of detergent would have greatly improved this
experiment as knowing the minimum amount of detergent that could be used to
obtain the greatest result would enable a justified recommendation. As well as
this, to improve the experiment, different brands of washing detergent should
have been tested as other brands may have been more effective.
Recommendation
It is recommended that a tablecloth stained with Turmeric is
washed in a detergent containing enzymes, at a temperature of 70 degrees
Celsius, with a concentration of laundry detergent equal to 1.25g/0.1L,
agitation and a saturation time of greater than 30 minutes. This wash will,
without fail, deliver the best results and clean the tablecloth completely.
However, it is understood as a restaurant business the economic impact of this
wash would be too great for the return. Considering this, there are two viable
options that would satisfy both the economic needs and cleaning standards of
the restaurant. Assuming that a colour greater than ‘20’ on the colour scale
was accepted as ‘clean’, the cost of cleaning the tablecloth can be reduced
greatly. The first option would be to use a home brand detergent (one without
enzymes) in a hot wash, with agitation (as in a normal washing machine) for a
period of 30 minutes or longer. The home brand detergent is consistently cheaper
than the premium enzyme detergent however the advantages of the enzyme
detergent can be nullified through the use of other increasing factors. The
other option is to use an enzyme detergent in a warm wash with agitation for a
period of 30 minutes or longer. The use of an enzyme detergent decreases the
temperature needed to obtain a clean tablecloth. The benefits in the reduction
of electricity cost (using a warm wash instead of a hot wash) compared to the
reduction in detergent cost will determine which of these two recommendations
should be used at the restaurant.
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