Cooling curve practical
A cooling curve is a line graph that shows the change in states of
matter with time. By drawing a cooling curve, it is to be noted that
we must put the dependent variable on the Y-axis and the
independent variable on the X-axis. A cooling curve has different
shapes of representation. Its shape depends upon oxidation, water,
and particulate. The following two practical methods show how to
draw a cooling curve for stearic acid and paraffin wax.
Stearic acid
Equipment list:
250cm3 beaker
Clamp stand
Heatproof mat
Stopwatch
Boiling tube
Thermometer (digital)
Thermometer (analogue)
Bunsen burner
Tripod gauze
Ice
Stearic acid
Calibration:
While doing the practical method the instrument or the equipment
used in this method must be calibrated to get accurate results. In this
practical, the thermometer must be calibrated first. This can be done
by the following methods,
, Digital thermometer:-
To calibrate the digital thermometer, the beaker must be filled
with cold water, including ice. After setting the apparatus the
thermometer must be put inside the cold-water end and
turned on. Wait until the thermometer reaches a certain
temperature when it is calibrated. The temperature must be
between 0-3 degrees Celsius.
Analog thermometer:-
To calibrate the analogue thermometer, the beaker must be
filled with cold water, including ice. Same as the digital
thermometer after setting the operators the analogue
thermometer must be put inside the cold water. Wait until the
thermometer reaches a certain temperature when it is
calibrated. This temperature also must be between 0-3 degrees
Celsius.
Method:
First an apparatus should be set up. As shown in the figure,
After setting up the apparatus stearic acid is added to the
boiling tube which is being held by the clamp stand.
, After adding the stearic acid, the boiling tube is moved
downward so that the amount of stearic acid added is
completely submerged in the hot water.
Then after the flame is turned on carefully by lightning the
Bunsen burner.
Both thermometers must be put inside the boiling tube having
stearic acid to record the temperatures every minute.
Water should be heated gently until it reaches a certain
temperature which is about 70 degrees Celsius.
Then as the experiment continues and goes on every minute
temperature is noted.
After the stearic acid melts completely, the boiling tube is lifted
out from the hot water using a clamp stand.
When it started cooling the temperature is again noted in each
minute until it reaches a certain temperature that is 30
degrees Celsius. Wait until it again turns back to solid.
It should be noted that the beaker of hot water is removed
from under the boiling tube so that no steam reaches the tube.
As it will allow it to cool down more quickly.
The point when it started melting and started cooling must be
noted.
Risk assessment:-
There are different types of risks while doing this type of practical
method so they must be done carefully and should be assessed.
some of these risks are as follows,
While doing this practical method lab coat should be used.
The beaker should be washed and cleaned before use.
Lightning the Bunsen burner should be done carefully because
it may burn the hand.
while doing this practical method safety goggles should be born
so that there is no risk to get acid into the eyes.
A cooling curve is a line graph that shows the change in states of
matter with time. By drawing a cooling curve, it is to be noted that
we must put the dependent variable on the Y-axis and the
independent variable on the X-axis. A cooling curve has different
shapes of representation. Its shape depends upon oxidation, water,
and particulate. The following two practical methods show how to
draw a cooling curve for stearic acid and paraffin wax.
Stearic acid
Equipment list:
250cm3 beaker
Clamp stand
Heatproof mat
Stopwatch
Boiling tube
Thermometer (digital)
Thermometer (analogue)
Bunsen burner
Tripod gauze
Ice
Stearic acid
Calibration:
While doing the practical method the instrument or the equipment
used in this method must be calibrated to get accurate results. In this
practical, the thermometer must be calibrated first. This can be done
by the following methods,
, Digital thermometer:-
To calibrate the digital thermometer, the beaker must be filled
with cold water, including ice. After setting the apparatus the
thermometer must be put inside the cold-water end and
turned on. Wait until the thermometer reaches a certain
temperature when it is calibrated. The temperature must be
between 0-3 degrees Celsius.
Analog thermometer:-
To calibrate the analogue thermometer, the beaker must be
filled with cold water, including ice. Same as the digital
thermometer after setting the operators the analogue
thermometer must be put inside the cold water. Wait until the
thermometer reaches a certain temperature when it is
calibrated. This temperature also must be between 0-3 degrees
Celsius.
Method:
First an apparatus should be set up. As shown in the figure,
After setting up the apparatus stearic acid is added to the
boiling tube which is being held by the clamp stand.
, After adding the stearic acid, the boiling tube is moved
downward so that the amount of stearic acid added is
completely submerged in the hot water.
Then after the flame is turned on carefully by lightning the
Bunsen burner.
Both thermometers must be put inside the boiling tube having
stearic acid to record the temperatures every minute.
Water should be heated gently until it reaches a certain
temperature which is about 70 degrees Celsius.
Then as the experiment continues and goes on every minute
temperature is noted.
After the stearic acid melts completely, the boiling tube is lifted
out from the hot water using a clamp stand.
When it started cooling the temperature is again noted in each
minute until it reaches a certain temperature that is 30
degrees Celsius. Wait until it again turns back to solid.
It should be noted that the beaker of hot water is removed
from under the boiling tube so that no steam reaches the tube.
As it will allow it to cool down more quickly.
The point when it started melting and started cooling must be
noted.
Risk assessment:-
There are different types of risks while doing this type of practical
method so they must be done carefully and should be assessed.
some of these risks are as follows,
While doing this practical method lab coat should be used.
The beaker should be washed and cleaned before use.
Lightning the Bunsen burner should be done carefully because
it may burn the hand.
while doing this practical method safety goggles should be born
so that there is no risk to get acid into the eyes.
