Unit 2B applied science DISTINCTION

Unit 2: Assignment 2: Melting and boiling points
Unit 2: Practical scientific procedures and techniques
B: Undertake calorimetry to study cooling curves
Keeping up the standards
In this assignment the cooling curve will be used to determine the rate of cooling substances, obtain
data using different equipment to construct cooling curves, analyse the rate of the cooling of
substances from the recorded data using the cooling curves to draw conclusion and evaluate the
accuracy of practical work in calorimetry in relation to the analysis of the cooling curves.
Aim
The aim for the practical was the be able to calibrate different types of thermometers and as well be
able to determine the melting point of the paraffin wax to find the cooling points by using the
cooling curve graphs.
Calibration of the thermometers
Liquid thermometers
Equipment
 Boiling hot water
 Beaker(s)
 Timer
 Ice
 Alcohol thermometer
 Water
 Alcohol thermometer
Method
The calibration of the mercury and alcohol-based thermometers was done by using cold and hot
water. The method was to start with filling a large beaker (consisting of 250cm³) filled with ice
(crushed) and adding a bit of unfiltered water(tap water). The crushed ice was then stirred
consistently with a glass rod and then left to stand untouched for around 2-3 minutes. The
thermometer was then placed into an empty beaker and recorded every 30 seconds and then I
recorded the results on a suitable table which is shown below.
Results
Time in seconds Temperature in Celsius
0 Seconds (After 3-minutes cool) 2.5 Celsius
30 Seconds 1.5 Celsius
60 Seconds 0.5 Celsius
120 Seconds 0 Celsius

, Risk assessment

Hazard Risk How will you avoid the Actions (what will
(what will cause the (what could happen) risk? (what specific action you do if an action
danger?) will you take?) takes place?)
Burns. Burns due to boiling Wear PPEs in this case a Compress and
water. lab coat, gloves and pour cold water on
appropriate footwear the affected area
would be suitable. to minimises the
damage.
Cuts. Cuts due to the glass Wear PPEs including Compress and
or thermometer. gloves and a lab coat pour cold soapy
water on the
affected area to
minimise the
overall damage.
Digital thermometers
Equipment
 Water
 Digital thermometers
 Ice
 Beaker(s)
 Boiling hot water
 Timer
 Paraffin Wax
 Digital thermometer
Method
After that I obtained approximately 10 g of Paraffin wax and placed it into a boiling tube. I then
placed the boiling tube into a beaker with freshly boiled water. A digital thermometer was then
placed into the boiling tube which to record the drop in temperature as the paraffin wax was started
to cool down. I then observed how the paraffin wax started to heat up and then started to melt. I
recorded the highest temperature of the present liquid paraffin wax and then removed the boiling
tube from the beaker of boiling water, I allowed the liquid to cool down. I started to record the
temperature of the liquid paraffin wax in an interval of 20 seconds for approximately 260 seconds,
until the liquid started to convert from a liquid phase into a solid state. I then produced a cooling
curve graph of the paraffin wax with having temperature on y-axis and time in x – axis. I then draw a
curve of best fit and calculated the rate of cooling from the drawn gradients on the graph paper. I
finally then analysed the results. As you can see below;




Time in seconds (s) Temperature in Celsius (c)
0 73
20 62