Unit 2 - Practical Scientific Procedures and Techniques
Institution
PEARSON (PEARSON)
A report evaluating the skills I have learned during the course and how they will be used when I progress. The contents of this evaluation will aid in self-reflection of learned skills and give a structure to format your work. This report received a distinction.
Unit 2 - Practical Scientific Procedures and Techniques
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How Am I Doing?
Luke David Farrar
Introduction
In all scientific professions, it is important to maintain evidence of continuing
professional development. Reflection is essential if people are to make the most of their
learning experience. As such, I will evaluate the skills I have learned during the four major
experiments I have carried out, as well as how they will apply to my future careers/if at all.
Skills developed in…
Titration
While carrying out titration, I was required to correctly measure out a primary
solution and a standard solution. I used graduated pipettes to measure out my sodium
carbonate solution, as well as mixing techniques to perform the titration and record a
reaction. As I was measuring out small amounts of substances, it was important to consider
the meniscus when reading the measurements from burettes and graduated pipettes. While in
a thin container, many liquids tend to curve upwards around its edges. When this occurs, the
lowest point of the liquid is used in the measurement to keep results universal.
During these tests I needed to only add the required solution to cause a reaction, so
patience and control over the speed of substance release from the burette was necessary to
ensure that the precise amount of solution needed to cause a reaction was recorded. Using
these skills will help me in the future if I am required to measure out samples from a crime
scene and give me the patience to fully carry out a scientific investigation of substances. This
includes the correct usage of phenolphthalein in the experiments to indicate a colour change,
which will be useful when carrying out different titration experiments.
I developed the skill to follow a variety of methods for experiments which I had never
performed before. Learning how to follow a method is critical for work in any scientific field,
as is the ability to create one myself using the knowledge gained from following a variety of
methods, including the layout of a scientific report to display accumulated data. The
calibration of equipment, such as a Hanna held pH meter, was necessary to ensure that the
solutions I was testing were at the correct pH levels. Analysing the pH contents of items is
extremely useful in a scientific field. For example, when analysing foods, or, in a forensic
field, when analysing soil to identify the type of soil present.
Once the titration had been successfully carried out, I used calculations to determine
the concentration of the solution using the formula Mols = Concentration x Volume. This
caused me to need to rearrange the equation to find concentration (C=M/V) and balance a
symbol equation to perform the calculations. The answer of this equation gave me the
mol/dm3 of the sample. Having the ability to perform calculations to find the mols,
concentration, and volume will be useful when examining any liquid—such as blood from a
crime scene—to determine the nature of the sample by cross-analysis. After this, I needed to
plot the results into graphs, which required me to draw and dot a line graph with correct
values to visually represent the results obtained, which is a useful skill to display data in a
readable format when presenting to a group or individual in most professions.
, Colorimetry
While performing colorimetry, I have been required to produce/measure samples of
varying concentrations. To do this, the use of a graduated pipette was necessary to correctly
measure out samples within 1ml of each other. Once multiple of these samples had been
measured out, I needed to mix them together to create 11 mixtures (2 pure) of differing
concentrations for testing using a colorimeter. However, before using a colorimeter, it needed
to be calibrated. This was done using a solution with an extremely low concentration (water)
and ensuring that the absorbance reader was maxing out, meaning that the colorimeter was
absorbing all the light through the liquid, which told us that the concentration was very low.
The same can be done using a solution with an exceedingly high reading, which would give a
low absorbance.
Correct usage of filters in the colorimeter were necessary as they needed to be a
different colour to that of the solution being tested. This would allow that colour to be visible
to the colorimeter after travelling through the solution, so it was necessary to use the
necessary filter to get accurate absorbance readings.
Calculating concentrations using absorbance readings was a necessary skill to develop
as it allowed the analysis of the concentration of any coloured solution using a colorimeter.
The was completed using the Beer-Lambert law, a mathematical law that directly links the
concentration and absorbance of a coloured solution. This equation uses the absorbance (no
units), molar absorptivity (L/mol cm), and path length (cm—distance travelled in the
colorimeter)
I learnt how to draw calibration curve graphs to measure the absorbance of an
unknown solution by comparing it to that of a known solution. This is a straight graph where
colorimetry results can be plotted after testing with known solutions using the absorbance %
and concentration in mols. Plotting graphs like this has helped when creating cooling curve
and titration curve graphs in other units, as well as assisting in my overall betterment at graph
drawing, which I consider one of the aspects I am weakest at when performing experiments,
so it was helpful to be able to work on my effectiveness at drawing them in this unit.
Calorimetry
When performing calorimetry, I used a mercury filled liquid thermometer to measure
the heat loss of boiling water on its own and with various affecting factors. As I needed to
collect quick readings of the boiling water once it had reached 100ºC it was necessary to
micro-manage multiple things at once. This included starting the stopwatch, carefully pouring
out the boiling water from a kettle into the beaker, allowing the thermometer to settle at the
correct temperature, and record the temperature within a minute; then continuing to record
the loss of heat at set intervals. Performing calorimetry has helped me manage my time more
effectively to ensure that my results are accurate and performed within a set timeframe. At
times this was very difficult and required multiple tests and help from my partner but, now
that I have completed the tests, I am confident that I could carry them out again with little
trouble compared to the initial tests.
Using my knowledge of dot and line graphs, including the correct placement of a line
of best fit and curves of best fit, I found the plotting of a cooling curve graph to be much
easier than graphs initially were to me. Trend graphs are important in several managerial
positions—especially when working for a tech company—and trend analysis has been
exceedingly useful in forensic fields such as forensic taphonomy (to measure the rate of heat
loss in a body) and forensic anthropology (when measuring the average temperature over a
set period to determine an average ambient temperature). Once the graph was plotted, I
placed tangents in various location on the graph to calculate the rate of cooling in that area.
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