This is part of the unit 2 assignment which is the physics part. I secured a merit in this piece of coursework as more detailed sentences were needed. Easy structure to follow
Assignment 2 using calorimetry to study cooling curves
Part 1
The aim of this experiment was to determine temperature and physical changes
while studying cooling curves using paraffin wax and stearic acid.
This assignment required me to show and explain how I used different techniques
to use calorimetry to study cooling curves. Calorimetry is when a calorimeter is
used in scientific experiments to measure changes of chemical reactions, state
and phase in relation to the heat transferred or absorbed. A calorimeter is the
object used in the experiment used for calorimetry and is the container such as a
glass beaker or boiling tube, which a thermometer can be placed into to measure
temperature change during a reaction.
Equipment
- Polystyrene cup
- Deionised ice
- 2 x beakers
- Distilled water
- Ice cubes
- Glass stirring rod
- Bunsen burner
- Gauze
- Heat proof mat
- Tripod
- Tongs
- Liquid filled thermometer (alcohol)
- Infrared thermometer
Calibration of thermometers
In my experiment I used two types of thermometers. An alcohol in glass
thermometer (liquid-filled) and an infrared thermometer (electronic). I did this to
investigate which type of thermometer gave me the most accurate reading during
the calibration process to ensure when carrying out later experiments that I was
able to gain valid results.
Ice method
1. Fill a beaker with deionised ice cubes into the polystyrene cup, and add
some distilled water
2. Stir the ice and water and let sit for about 3 minutes
,Assignment 2 using calorimetry to study cooling curves
3. Once the beaker is full of a liquid consistency, place the thermometer into
the beaker, making sure the bulb is fully in the water and also not touching
the sides or bottom of the beaker
4. After about 30 seconds, measure the temperature and it should read 0(C)
5. If your thermometer doesn’t read 0 degrees Celsius, record the difference
and remove the thermometer from the beaker
6. Repeat this method 3 times and record your results in a table
Boiling water method
1. Pour some distilled water into a beaker
2. Set up a Bunsen burner and bring the water to boiling point
3. Insert the thermometer, making sure that it doesn’t touch the sides or the
bottom of the beaker
4. The thermometer should read 100(C)
5. If your thermometer doesn’t read 100 degrees Celsius, record the
difference and remove the thermometer from the beaker
For both the ice and boiling water methods of calibration above the instructions
are for a liquid filled thermometer as you insert it into the beaker. For an infrared
thermometer carry out the same procedure but instead of placing the
thermometer into the beaker, hold the thermometer very close to the liquid and
press the power button to record the temperature.
,Assignment 2 using calorimetry to study cooling curves
Mean 101.7 0.65
From my results, I have chosen to use the liquid filled thermometer due to it
being more accurate. This is shown by the difference in the freezing repetitions as
the mean of the liquid filled thermometer is 0.06 meaning only + 0.06 away from
0 whereas the infrared thermometer is + 0.65 away. This shows how the liquid
filled thermometer is more accurate as the mean is lower and the difference away
from the actual value (0 degrees) is also lower. The liquid filled thermometer in
both methods gave the most accurate results as it gave a reading on both
occasions closest to the actual value.
Part 2-
Equipment
- Boiling tube with paraffin wax in
- Boiling tube with stearic acid in
- Beaker
- Bunsen burner
- Gauze
- Heat proof mat
- Tripod
- Tongs
- Liquid filled thermometer
- Test tube rack
- Stopwatch
Producing a cooling curve
In this experiment I used two substances to produce a set of results to show the
cooling curves. I used Paraffin wax and Stearic acid in my experiment. They both
use the same method of bringing the substance to a boiling point and at intervals
recording the temperature.
Cooling Curve Method
1. Take 2cm (as any less would not be enough substance to be accurate and
anymore would take too long to melt) of the Paraffin wax and place it into a
boiling tube
2. Place the boiling tube into a beaker of boiling water
3. Heat up the wax ensuring it has fully melted into a liquid state
, Assignment 2 using calorimetry to study cooling curves
4. Insert the chosen thermometer into the boiling tube (making sure it doesn’t
touch the edges or the bottom to obtain valid results) and record the
highest temperature of the liquid Paraffin wax
5. Remove the boiling tube from the beaker using tongs and place into a test
tube rack
6. Allow the Paraffin wax to start to cool
7. Record the temperature of the wax over a period of time (every 1 minute)
until the wax is back into a solid state and the thermometer reads room
temperature (around 24 degrees Celsius)
Use this exact method for Stearic acid, ensuring you take temperature recording
every 1 minute.
Cooling explanation
The process of cooling will occur in many ways. One way is by latent heat which is
when a substance is changing state, heat energy is taken in or given out to the
surroundings. Another way is by conduction which is when heat energy is
transferred from a solid (solid Paraffin wax) when there is a difference in the
temperature, such as going from 24 (C) to 54 (C).
Transfer of heat energy into a cooling process occurs through the surface of the
material. Due to a boiling tube having a relatively small surface area this will
affect cooling as the substance will take longer to cool. If I had used a beaker with
the substance in instead of a boiling tube this would cool much quicker as the
beaker has a large surface area.
In this particular experiment I didn’t put a lid on the beaker, meaning air was able
to get in whilst carrying out the investigation. This would make the cooling
process speed up due to no insulation from a lid. Having no lid allowed air from
the room to flow across the substance therefore cooling the Paraffin wax and
Stearic acid quicker. In my investigation, the room temperature was 24(C) and the
start temperature of Paraffin wax was 85(C), therefore, it needed to cool by 61(C)
to get back down to room temperature and so using no lid allowed it to cool
quicker.
Cooling of Paraffin wax and Stearic acid results
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