Unit 2: Practical Scientific Procedures and Techniques
Learning aim D: Review personal development of scientific skills for laboratory work
Appraisal
After having completed my probationary period at an independent materials science company, I have successfully
completed all experiments that were required to be carried out as part of Unit 2: Practical Scientific Procedures and
Techniques. These experiments were calorimetry, titration, colorimetry and chromatography. Throughout the
duration of my career at the independent materials science company, I have developed my ability to apply prior
scientific knowledge to the experiments that were carried out. In this report, I will be commenting on the skills I
have developed over the course of Unit 2, my strengths while carrying out the practicals and the skills that myself
and my teachers have identified as areas for improvement.
Skills that I could complete before Unit 2:
- Using a liquid thermometer to record the temperature
- Using a ruler to measure the distance
- Using balances to measure the mass of substances
- Using measuring cylinders to measure the volume of solutions
- Using universal indicator to measure the pH of a solution
- Repeating practicals to ensure that the data collected is accurate
- Calculating a mean value from my results
- Carrying out paper chromatography of inks
- Calculating Rf values of components separated by chromatography
- Setting up equipment properly
Skills that I can now complete after completing Unit 2:
Calibrating equipment- I am now aware that calibration is one of the first and most important steps before
beginning a practical which involves measuring equipment. I have mainly developed this skill during calorimetry,
titration and colorimetry.
Constructing cooling curves and drawing tangents to find the rate of cooling of a substance- I already had little
knowledge of heating curves and cooling curves but Unit 2 has allowed me to gain an understanding of what
happens at each point on the graphs in terms of particle movement and intermolecular forces.
Calculating the concentration of a solution from titration- I was confident with how to calculate the concentration of
solutions from my studies at GCSE and so I was able to apply this prior knowledge to titration to calculate the
concentration of hydrochloric acid and sodium hydroxide.
Identifying the endpoint of a titration using methyl orange indicator- At first, I initially thought that titrations could
only be carried out by working out the neutralisation point of a solution. I have now learnt that coloured indicators
such as methyl orange can be used to determine when a titration has been completed.
Using colorimetry to calculate the absorbance of solutions- I can now make dilute solutions of different
concentrations to test in a colorimeter so that I can measure how much light is able to pass through.
,Unit 2: Practical Scientific Procedures and Techniques
Learning aim D: Review personal development of scientific skills for laboratory work
Carrying out chromatography of different substances other than ink- I already had some prior knowledge of the
applications of chromatography before starting Unit 2 such as in forensics and drug testing. During this unit, I was
able to develop my understanding of chromatography by carrying out chromatography of plant pigments.
Carrying out TLC chromatography- During my GCSE studies, I thought that paper chromatography was the only way
that one can carry out chromatography. I have now learnt about the composition of TLC plates and how they can
affect the rate of separation in different mixtures
Calorimetry
Calorimetry is a process which looks at measuring the amount of heat absorbed or released during a chemical
reaction. The purpose of this task was to observe changes in temperature and the state of matter. I carried out this
procedure for two substances: paraffin wax and stearic acid. In terms of calorimetry, I had not carried it out before
beginning my studies for Unit 2 so most of the steps required for the experiment were fairly new to me.
Equipment
A new piece of apparatus that I used was digital thermometers; I used this for the calibration process to compare
which type of thermometer would be most effective for the calorimetry practical. I had not used these prior to
starting Unit 2 but I had used liquid filled thermometers during my GCSE studies to measure temperature changes
of substances. Digital thermometers have several uses in industry and in the home such as food preparation,
manufacturing, medical and scientific testing and procedures. [1]
Safety precautions
When using the Bunsen burner, I left it on the safety flame when it was unsupervised. During the practical, I stayed
a slight distance from the Bunsen burner to prevent injury. I wore goggles while reading the thermometer during
calorimetry. If glass beakers broke, I was informed not to clean it up and instead inform my teacher.
Personal competencies
My behaviour was of a good standard while I was setting up and carrying out the experiment. I followed all safety
procedures appropriately and that I worked safely during the practical. For paraffin wax, my role during the practical
was to check the temperature of the wax and inform my peer so that they can record the values in our results table.
However, I struggled to do this well because when we had finished melting the wax and started recording results,
some of the steam from the melting process made the thermometer scale unclear as it was covering the insides of
the test tubes. Because of this, rather than looking from the sides of the test tube to read the temperature, I had to
look inside to see what the thermometer reading was. For stearic acid, my role during the practical was to keep an
eye on the stopwatch and inform my peer of when to check the reading on the thermometer The quality of my
written work was of a good standard as I kept my lab notebook away from the workspace at all times to prevent
burns from the Bunsen burner. I managed to sketch a results table which showed how the amount of time affects
the rate of cooling. In terms of communication and cooperation, I believe that at times this competency was not
followed as well. This was because during the calibration process, I was not that observant. When I was calibrating
the two thermometers, my peer identified that at times I accidentally let the bulb of the thermometer reach the
bottom of the beaker. This resulted in inaccurate readings so I had to repeat the calibration process to ensure that
the thermometer was calibrated correctly. When carrying out calorimetry of paraffin wax and stearic acid, steam
accumulated inside the test tube and obscured the thermometer readings at times. This made it difficult to
accurately read the thermometer, which meant that my results could have been inaccurate by 1-2°C. After carrying
out calorimetry, I cleared the workspace and ensured that the area that I was working at was cleaned properly.
, Unit 2: Practical Scientific Procedures and Techniques
Learning aim D: Review personal development of scientific skills for laboratory work
Health and safety was crucial for doing this experiment. For example, during the cooling curve practical, we used
boiling water to melt both substances. If the boiling water spilt on the floor, it could cause potential injury as this
would be a slip hazard. Knowing how to safely conduct an experiment would ensure that I will obtain accurate
results while handling slightly harmful chemicals and substances. This skill will also help me when I study other units
in the Applied Science BTEC course as health and safety is a critical skill to consider when completing experiments.
Strengths and weaknesses
I was able to accurately read liquid thermometers by bending down to read them. I also now have good experience
with digital thermometers. As well as how to carry out the calorimetry practical, I also learnt how to find the rate of
cooling from constructing a cooling curve; my teacher said that I was able to get a good set of data to plot my
cooling curve correctly. However, due to the slight lack of communication between myself and my peer for the
experiment with paraffin wax, it took longer for it to cool and turn into a solid compared to stearic acid. This was
because as soon as we melted the wax, I forgot to start the stopwatch immediately to observe the rate of cooling.
Because of this, we had to leave the wax to cool for a further five minutes to ensure that it had fully changed state.
Comparison to classmates
In comparison to my peers, I think that I carried out this experiment well because they worked sensibly and
obtained similar results to mine, leading to overall low percentage errors which showed that my findings were
reliable. By actively communicating with my peer, we were able to get a set of accurate readings which showed the
rate of cooling over time for both paraffin wax and stearic acid. One group had accidentally knocked over a beaker
and they had to repeat their practical again because of this. Me and my group hadn’t broken any equipment during
the experiment and we were able to cooperate effectively to obtain our results.
Area of improvement
Based on my feedback from my physics supervisor, I would have improved my findings by allowing the paraffin wax
to cool for a few minutes longer to ensure that it had completely changed state, which could have resulted in
greater accuracy. I would also repeat the experiment with paraffin wax for at least two more attempts, calculating a
mean temperature at each time interval. This would aid in increasing the reliability of my findings and ensuring that
my results are of higher quality. I would also consider wrapping the beaker in foil, using a lid, or using air bubble
packaging to keep it well insulated. This would prevent convection and other heat loss to the environment, making
my results slightly more accurate. As with paraffin wax, I would repeat this experiment for two more attempts to
ensure reliability of my findings and perhaps calculate a mean for the temperature at each time interval. My physics
supervisor recommended that I learn more about data loggers and temperature probes. This will allow me to record
temperature over a continuous period of time at smaller intervals.
Transferability to other units and future progressions
The skills that I learnt in this practical will be useful for when I study Unit 4B as we will be required to know how to
measure the boiling point; this will be of benefit because we measured the boiling point of water while calibrating
thermometers. I could also carry out calorimetry in a lab so that I will be able to accurately measure the rate of
cooling of certain substances. This could lead to results of an improved accuracy as there would be more controlled
variables such as the temperature of the room and the accuracy of the temperature readings on the thermometers.
Titration
The purpose of this task was to determine the concentration of hydrochloric acid and sodium hydroxide by using
different titration methods. I carried out an acid-base neutralisation titration of hydrochloric acid to calculate the
