Unit 2 Assignment B- Cooling Curves
I was given the task to determine the rate of cooling of stearic acid and paraffin wax by constructing
a cooling curve. A cooling curve is a graph that shows the changes in state of a substance as it cools.
I decided to do this by melting a solid sample of each substance and then using an appropriate
thermometer to record the temperature of the substance at regular intervals to plot a graph until
the substance became solid again.
Calibration-
Before performing my calorimetry experiments, I had to calibrate my equipment so that I would get
accurate and precise results. The equipment that I needed to calibrate was my thermometer. I had
access to a digital and alcohol thermometer and therefore had to choose which one I would use for
my experiments. Calibration was useful as it enabled me to see which of my thermometers were
more accurate and therefore more suitable to use. To calibrate my equipment, I decided to conduct
two small experiments of placing them in a beaker full of boiling water and then into ice to see what
they recorded the temperature as. I knew that the reading for the ice should be 0°C and the boiling
water should be 100°C as these are waters boiling point and melting point. I ensured to leave my
thermometer in the beaker until the readings settled so that I would not write down an incorrect
result. I also made sure I did not allow the thermometer to touch the sides of the beaker as I knew
that would impact my result as it would not just be recording the temperature of the water, instead
it would read the temperature of the beaker itself which I do not want to know. I repeated my
readings 3 times so that I could work out the mean as it would give me a more accurate and precise
result. Overall, I decided to use the digital thermometer as it was only incorrect by 0.2°C whereas
the alcohol thermometer was incorrect by 3°C. The digital thermometer also has a higher degree of
accuracy as it gives the temperature to 2d.p., whereas with the alcohol thermometer, it can only
really be read to a full °C or maybe 0.5°C. The alcohol thermometer is also harder to read therefore
it was a logical choice to not choose to use this when performing my calorimetry experiments.
Boiling-
Temperature 1 Temperature 2 Temperature 3 Average
(°C) (°C) (°C)
Digital 100.1 100.2 100.3 100.2
Thermometer
Alcohol 96.0 98.0 97.0 97
Thermometer
Ice-
Temperature 1 Temperature Temperature 3 Average
(°C) 2 (°C) (°C)
Digital 0.3 0.2 0.1 0.2
Thermometer
Alcohol 3.0 3.0 3.0 3.0
Thermometer
Health and Safety-
, During my experiment there were several health and safety concerns that I needed to consider.
First, I needed to ensure I tied back my long hair and removed any possible obstructions, such as
bags and coats, from where I was going to perform my experiment. This reduced the chance of me
tripping and falling over. As I was working with glassware, there was the risk of broken glass and
receiving cuts. By removing obstructions, it reduced the chance of this occurring. There was also a
risk of burns as I was working with boiling hot water and a hot plate. I ensured that I was careful
when handling the equipment and did not try and move the beaker whilst it was still hot. I also wore
googles and a lab coat to ensure that if there were any splashes of boiling water or any other liquid
then it wouldn’t harm or irritate my eyes and skin. I had to take care when working with my hot
plate as there was wires and cables around which I had to ensure were not broken to prevent any
possible electrical shocks. I also had to place my hotplate in a strategical position so that the wires
did not wrap wound any equipment and could be placed in the plug socket without having to
stretch or get in the way of anything.
Stearic Acid-
In order to construct my cooling curve for my stearic acid, I first had to melt it by placing 8g into a
glass test tube and then placing that test tube into a clamp and lowering it into a 250cm3 beaker
full of about 150cm3 of hot water. I then placed my beaker onto a hot plate and proceeded to boil
it. I waited until my stearic acid was completely melted and then I carefully removed it from the
beaker and left it at the side. I immediately placed my digital thermometer into the liquid and
started the timer. I decided not to use a lid but rather allow my stearic acid to cool openly in the air
as I did not have much time and so I knew this would be the best way to rapidly cool my substance
while still managing to get accurate results. I proceeded to record the temperature of my stearic
acid every minute until it became solid. Overall, I recorded the temperature for 40 minutes. Using
these results I plotted a graph, and I was left with the cooling curve of stearic acid.
I was given the task to determine the rate of cooling of stearic acid and paraffin wax by constructing
a cooling curve. A cooling curve is a graph that shows the changes in state of a substance as it cools.
I decided to do this by melting a solid sample of each substance and then using an appropriate
thermometer to record the temperature of the substance at regular intervals to plot a graph until
the substance became solid again.
Calibration-
Before performing my calorimetry experiments, I had to calibrate my equipment so that I would get
accurate and precise results. The equipment that I needed to calibrate was my thermometer. I had
access to a digital and alcohol thermometer and therefore had to choose which one I would use for
my experiments. Calibration was useful as it enabled me to see which of my thermometers were
more accurate and therefore more suitable to use. To calibrate my equipment, I decided to conduct
two small experiments of placing them in a beaker full of boiling water and then into ice to see what
they recorded the temperature as. I knew that the reading for the ice should be 0°C and the boiling
water should be 100°C as these are waters boiling point and melting point. I ensured to leave my
thermometer in the beaker until the readings settled so that I would not write down an incorrect
result. I also made sure I did not allow the thermometer to touch the sides of the beaker as I knew
that would impact my result as it would not just be recording the temperature of the water, instead
it would read the temperature of the beaker itself which I do not want to know. I repeated my
readings 3 times so that I could work out the mean as it would give me a more accurate and precise
result. Overall, I decided to use the digital thermometer as it was only incorrect by 0.2°C whereas
the alcohol thermometer was incorrect by 3°C. The digital thermometer also has a higher degree of
accuracy as it gives the temperature to 2d.p., whereas with the alcohol thermometer, it can only
really be read to a full °C or maybe 0.5°C. The alcohol thermometer is also harder to read therefore
it was a logical choice to not choose to use this when performing my calorimetry experiments.
Boiling-
Temperature 1 Temperature 2 Temperature 3 Average
(°C) (°C) (°C)
Digital 100.1 100.2 100.3 100.2
Thermometer
Alcohol 96.0 98.0 97.0 97
Thermometer
Ice-
Temperature 1 Temperature Temperature 3 Average
(°C) 2 (°C) (°C)
Digital 0.3 0.2 0.1 0.2
Thermometer
Alcohol 3.0 3.0 3.0 3.0
Thermometer
Health and Safety-
, During my experiment there were several health and safety concerns that I needed to consider.
First, I needed to ensure I tied back my long hair and removed any possible obstructions, such as
bags and coats, from where I was going to perform my experiment. This reduced the chance of me
tripping and falling over. As I was working with glassware, there was the risk of broken glass and
receiving cuts. By removing obstructions, it reduced the chance of this occurring. There was also a
risk of burns as I was working with boiling hot water and a hot plate. I ensured that I was careful
when handling the equipment and did not try and move the beaker whilst it was still hot. I also wore
googles and a lab coat to ensure that if there were any splashes of boiling water or any other liquid
then it wouldn’t harm or irritate my eyes and skin. I had to take care when working with my hot
plate as there was wires and cables around which I had to ensure were not broken to prevent any
possible electrical shocks. I also had to place my hotplate in a strategical position so that the wires
did not wrap wound any equipment and could be placed in the plug socket without having to
stretch or get in the way of anything.
Stearic Acid-
In order to construct my cooling curve for my stearic acid, I first had to melt it by placing 8g into a
glass test tube and then placing that test tube into a clamp and lowering it into a 250cm3 beaker
full of about 150cm3 of hot water. I then placed my beaker onto a hot plate and proceeded to boil
it. I waited until my stearic acid was completely melted and then I carefully removed it from the
beaker and left it at the side. I immediately placed my digital thermometer into the liquid and
started the timer. I decided not to use a lid but rather allow my stearic acid to cool openly in the air
as I did not have much time and so I knew this would be the best way to rapidly cool my substance
while still managing to get accurate results. I proceeded to record the temperature of my stearic
acid every minute until it became solid. Overall, I recorded the temperature for 40 minutes. Using
these results I plotted a graph, and I was left with the cooling curve of stearic acid.
