Unit 2- Practical Scientific Procedures and Techniques
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Summary unit 2: Learning aim B (Undertake calorimetry to study cooling curves)
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Unit 2- Practical Scientific Procedures and Techniques
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PEARSON (PEARSON)
My assignment covers topics such as thermometers and cooling curves in calorimetry. It discusses temperature and heat energy relationships, types of thermometers, calibration methods, and cooling curve interpretation. It should guide your assignment writing process. I've earned a Distinction* for i...
Unit 2- Practical Scientific Procedures and Techniques
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Physic assignment
In this assignment we are required to perform scientific techniques such as cooling curves of stearic
acid and paraffin wax. In order to demonstrate our skills in practical procedures of calibrating the
equipment and safety check of the chemical. The purpose of this experiment is to precisely calibrate
several types of thermometers, such as glass and digital thermometers, as well as to calculate the
melting and freezing points of stearic acid and paraffin wax, as well as to construct graphs and
tangens.
Calorimetry
Calorimetry is a technique for calculating how much heat is generated or absorbed during a chemical
reaction or a change in a substance's state. This can be identified whether a process is exothermic or
endothermic by measuring the change in temperature.
A thermometer is a scientific tool for measuring temperature that may be used to measure the
temperature of solid, liquid and gas. There are two main types of thermometers that are used to
measure temperature such as glass thermometers and digital thermometers. The thermometer is
made of glass and can withstand both boiling and freezing temperatures without breaking and it is a
good conductor of heat as it can measure high temperature. In addition, when using a glass
thermometer make sure to handle it with care as the glass thermometer is made of glass so it can
easily break. Whereas in a digital thermometer, it gives faster results than a glass thermometer and
gives more precise results than a glass thermometer. However, in a digital thermometer if the
batteries are out of energy then the result may not be accurate and it's difficult to predict when the
battery needs replacements therefore, It's better to use a glass thermometer.
Calibration of thermometer
It's necessary to calibrate a thermometer since it helps to minimise the measurement error and any
inaccuracies produced by the thermometer. It’s important to calibrate the thermometer since even a
few degree inaccuracies might affect the results. The method of calibrating the thermometer is to
start filling the kettle with water and press the bottom so the water starts boiling and pour the hot
water into a beaker then place the glass thermometer and digital thermometer inside the beaker.
Once the temperature reaches 100 c start taking the reading of the minimum and maximum
temperature of the glass and digital thermometer. Then the calibration of the thermometer was
done with cold water. Add ice into the beaker with cold water and place the glass and digital
thermometer inside the beaker and as the thermometer reaches minimum temperature start by
taking the reading.
Table 1: calibration results
Thermometer Min ice Mix boiling Zero error Reading error
Glass 1 0 101 0 + 0.5
Glass 2 2 103 2 + 0.5
Digital 1 0.90 101.20 0.90 + 0.05
Digital 2 0.80 102.50 0.80 + 0.05
,Sometimes the thermometer can't be calibrated so as a group we record the temperature difference
and subtract it from the minimum temperature. For example, if the thermometer shows that the
result is 2C instead of 0 then the thermometer is 2 C higher than the expected result.
When a substance is being heated it will absorb the heat energy which causes the attractive force
between the molecules to break, this leads to rearrangement of the practical because the attractive
force no longer holds them together as tightly. The difference between evaporation and boiling is
that when a substance transforms from state to another state e.g liquid to gas, condensation
happens as the molecules in the liquid will escape. The boiling is when the water is heated at high
temperature as the practical have enough energy to become gaseous. Whereas, evaporating is when
the practical escapes from the liquid surface as the practical has enough energy to change from
liquid to gas, but evaporating is a slower process compared to boiling. Furthermore, the
intermolecular molecules in freezing the energy are absorbed by the ice which causes bonds to break
between the ice molecules.
, Cooling curve of stearic acid
Stearic acid has been utilised in cosmetics, food, and hygiene products like soap and shampoo for
thousands of years. Stearic acid is a fatty acid that may be easily manufactured from vegetable and
animal fats and is utilised as a hardening agent in various products such as candles. The calorimeter
technique will be used to determine the temperature during a process in which heat is transferred
with the surrounding environment. In this experiment, the calorimeter is a glass beaker that may be
used in association with a thermometer to regulate temperature during a process in which heat is
delivered to the immediate environment. The calorimeter may be used to track endothermic and
exothermic processes, as well as physical states like freezing and melting.
Equipements:
- Tripod
- Clamp stand
- Boiling tube
- Water
- Beaker
- Gauze
- Timer
- Stearic acid
- Splint
- Bunsen burner
- Thermometer
Method
As working in a group we made sure to check the equipment that was safe to use. We started the
practical by filling the beaker with water until it was approximately three quarters full. Then we
connected the bunsen burner to a gas tap and made sure to place a heat proof mat under the
bunsen burner. Next, placed the gauze and the tripod above the bunsen burner and placed the
beaker onto the gauze. Next, we tighten the clamp holding the boiling tube so that the bottom of the
tube is entirely submerged in water. we made sure that the boiling tube is secured tightly as it's
possible to fall off and break which can cause injury and cut and should be cleaned. Before placing
the boiling tube inside the beaker we made sure that a thermometer and stearic acid was already
placed in the boiling tube. Also, we made sure that the concentration of stearic acid is 94%. Once the
equipment had been set up, turn on the gas tap and lit the bunsen burner making sure that the
bunsen burner was on safe flame before placing the bunsen burner under the tripod. Once we
placed the bunsen burner under the tripod, change the safety flame to the hotter blue flame. Then
we waited patiently for the stearic acid to melt until the temperature on the liquid filled
thermometer rose to 90. Once the temperature reaches 90℃ We take the boiling tube out of the
beaker and record the temperature of the stearic acid every 30 seconds until it hits 50 degrees
Celsius, at which point we stop recording.
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