Lab Report: Thermometer Calibration and Cooling Curve Experiment

Introduction

In this laboratory experiment, we conducted the calibration of two thermometers and subsequently compared their accuracy during the cooling curve experiment. The primary objective was to determine which thermometer yielded more reliable results when applied to the cooling curve practical. Accurate temperature measurements are crucial for obtaining precise data in various scientific applications.

The cooling curve experiment involves creating a graphical representation of the phase transitions that occur as a substance cools. Specifically, it reveals the stages at which a liquid transforms into a solid.

Additionally, cooling curves enable us to identify the freezing, melting, and boiling points of substances. In our experiment, we focused on stearic acid and paraffin wax as the substances of interest.

Risk Assessment

Hazard	Risk	Prevention
Fire	Burning limbs, room catching fire	Keep a safe distance, secure using a heat mat, wear goggles
Glass	Injuries from broken glass, slipping due to spillages	If glass breaks, call for assistance and avoid the broken glass. Walk slowly to prevent slipping on spillages. Get quality help now WriterBelle Verified writer Proficient in: Physics 4.7 (657) “ Really polite, and a great writer! Task done as described and better, responded to all my questions promptly too! ” +84 relevant experts are online Hire writer
Boiling Water	Burns from boiling water, potential spills	Exercise caution when dealing with boiling water. Walk slowly to avoid slipping on spilled water.
Paraffin Wax	Highly flammable substance, risk of fire	Avoid open flames and handle wax with care.
Chemicals	Irritation, burns	Wash hands thoroughly after chemical contact and wear eye protection (goggles).

Safety Precautions

• Goggles were worn throughout the experiment to protect the eyes from potential chemical splashes or contact with hot water.
• The beaker was positioned away from the edges of the workspace to prevent glass breakage and the spilling of hot water.
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• The test tube was securely placed in a test tube rack to minimize the risk of it falling and breaking.
• The experiment was conducted while standing to facilitate quick reactions and reduce the likelihood of accidents involving glassware.
• Adherence to the laboratory safety guidelines outlined in the CLEAPS sheet.

Equipment and Method for Thermometer Calibration (Boiling)

Equipment List:

• Digital thermometer
• Liquid thermometer
• Beaker
• Bunsen burner
• Tripod
• Wire gauze
• Heatproof mat
• Matches
• Water
• Stopwatch
• Goggles

Method:

1. Fill a beaker with water, ensuring it is more than half-full.
2. While in the laboratory, use a Bunsen burner (be sure to wear goggles).
3. Set up the Bunsen burner with a fire mat, tripod, and wire gauze.
4. Before igniting the gas, ensure the Bunsen burner is on the yellow flame setting to make the flame visible when lit.
5. Place the beaker on the wire gauze positioned on top of the tripod.
6. Ignite the Bunsen gas.
7. Once the Bunsen burner flames are on, adjust the flame to blue for increased effectiveness and wait for the water to boil.
8. When the water reaches its boiling point and bubbles start to rise to the top, carefully insert the thermometer into the water.
9. Ensure that the thermometer does not touch the sides or bottom of the beaker, as contact can lead to inaccurate results.
10. Wait approximately 30 seconds for the thermometer to stabilize and provide an accurate temperature reading.
11. After the initial 30 seconds, record the first temperature reading as the starting temperature (0 seconds).
12. For the subsequent readings, record the temperature every minute, up to the third minute.
13. By the end of the third minute, the temperature should have reached approximately 100°C or a value close to it.
14. If you initially used the liquid thermometer, repeat the entire process with the digital thermometer and compare the accuracy of the two thermometers.

Calibration Results:

Below are the temperature readings obtained from the digital and liquid thermometers during the boiling point calibration:

Time (minutes)	Digital Thermometer (°C)	Liquid Thermometer (°C)
0	100.1	100.0
1	101.9	102.0
2	102.1	103.0
3	102.0	103.0

Average Temperature (Digital Thermometer): 101.525°C

Average Temperature (Liquid Thermometer): 102.25°C

Equipment and Method for Thermometer Calibration (Cold)

Equipment List:

• Digital thermometer
• Liquid thermometer
• Beaker
• Ice
• Water
• Stopwatch

Method:

1. Fill the beaker with water, ensuring it is less than half full.
2. Add a sufficient quantity of ice to the beaker to completely cover the water surface. Allow it to sit for a few seconds.
3. Carefully place the thermometer into the water, ensuring it does not touch the sides, bottom, or ice to ensure precise results.
4. Allow the thermometer 30 seconds to stabilize and record the temperature of the water as the initial reading (0 seconds).
5. Record the temperature reading every minute, up to the third minute.
6. By the end of the third minute, the temperature should have reached 0°C or a value close to it.
7. If you initially used the liquid thermometer, repeat the entire process with the digital thermometer to compare the results and determine which thermometer is more accurate.

Calibration Results:

Below are the temperature readings obtained from the digital and liquid thermometers during the cold calibration:

Time (minutes)	Digital Thermometer (°C)	Liquid Thermometer (°C)
0	0.7	1.0
1	0.6	1.0
2	0.3	1.0
3	0.2	1.0

Average Temperature (Digital Thermometer): 0.45°C

Average Temperature (Liquid Thermometer): 1.0°C

Calibration Analysis

In the process of calibration, several critical considerations were made to ensure accurate and reliable results:

• The experiment was conducted multiple times to obtain the most precise outcomes.
• Meticulous attention was given to ensuring that the thermometers did not come into contact with the sides or bottom of the containers, minimizing sources of error.
• Strict adherence to safety precautions was maintained to mitigate potential hazards.
• The appropriate equipment was prepared and used for the practical calibration process.
• Both liquid and digital thermometers were calibrated to compare their accuracy.
• Special care was taken to address parallax errors in the liquid thermometers by ensuring readings were taken at eye level for the utmost accuracy.
• The correct water level was maintained, recognizing its impact on achieving more precise results, particularly regarding boiling and freezing points.

Choice of Calibration

In conclusion, the choice of the digital thermometer for calibration is justified by several key factors:

• The digital thermometer demonstrated superior accuracy compared to the liquid thermometer.
• It offered a higher resolution, providing temperature results in decimal points, enhancing the precision of the measurements.
• Conversely, the liquid thermometer has a fixed 1°C interval, necessitating rounding of results and diminishing their accuracy.
• Moreover, the liquid thermometer is susceptible to parallax error, requiring readings to be taken at eye level, which can be inconvenient and may introduce errors if not carefully executed.
• Handling the liquid thermometer at eye level also increases the risk of inadvertently touching its edges, potentially altering the results.

As evident from the table presented above, the digital thermometer consistently provided more accurate and precise readings, with temperature values expressed in decimal points, allowing for a higher degree of confidence in the results.

Cooling Curve Experiment

Required Equipment:

• Stearic acid within a test tube
• Paraffin Wax within a test tube
• Beaker (250cm³)
• Boiling water from a kettle
• Digital thermometer
• Heatproof mat
• Stirring rod
• Stopwatch
• Test tube rack
• Goggles
• Clamp

Method:

1. Boil water using the kettle and ensure it remains at a boiling point.
2. Pour approximately half of the boiling water into a 250cm³ beaker.
3. While the temperature of the boiling water is above 80°C, immediately immerse the test tube containing stearic acid into the beaker (starting with a higher initial temperature is preferred).
4. While the test tube is submerged, allow the stearic acid to melt into a liquid, stirring it gently during the melting process.
5. Once the stearic acid has completely transitioned into a liquid state, carefully insert the chosen digital thermometer into the test tube. Ensure that the initial temperature reading is above 70°C, preferably 80°C. If the temperature is lower, add more freshly boiled water to the beaker to raise the temperature of the acid.
6. When the temperature reaches above 70°C, remove the test tube from the beaker, start the stopwatch, and record the initial temperature reading.
7. Record the temperature every minute as the stearic acid cools down until it reaches approximately 35°C.
8. Throughout the temperature recording process, take care to prevent the thermometer from touching the sides or bottom of the test tube, as this could influence the readings and result in inaccuracies.
9. Repeat the entire procedure using paraffin wax.

Results Table:

Time (min)	Stearic Acid Temperature (°C)	Paraffin Wax Temperature (°C)
80	80
1	64.5	66.8
2	58.1	61.1
3	54.4	58.3
4	53.1	57.3
5	52.8	56.8
6	52.6	56.3
7	52.3	55.8
8	51.8	55.2
9	51.4	54.5
10	51	53.8
11	50.3	52.9
12	49.2	51.9
13	47.6	50.9
14	46.4	49.7
15	45.6	48.1
16	44.8	46.4
17	43.5	44.5
18	41.8	42.8
19	39.6	41.5
20	37.4	40.4
21	35.5	39.3
22	33.9	38.3
23		37.3
24		36.4
25		35.5
26		34.6

Behavior of Substances During Heating and Cooling

When both stearic acid and paraffin wax are subjected to heating, the atoms within these substances exhibit increased vibrational motion. As the substances are heated, the intermolecular bonds between the particles weaken, resulting in greater spacing between the molecules. Upon reaching the liquid phase, the intermolecular bonds are sufficiently weakened to allow the molecules to move more freely. These intermolecular bonds are comparatively weaker than covalent bonds, making them more susceptible to breaking under the influence of heat. The increased temperature provides particles with higher kinetic energy, causing them to move more rapidly.

Analysis:

During the experiment, several significant observations and trends were noted:

Stearic Acid:

• During the first 4 minutes, the stearic acid was in the liquid phase, exhibiting a cooling rate of 0.15°C per second.
• At the 11th minute, the stearic acid underwent a phase change from liquid to solid.
• During the solidification phase, the cooling rate decreased significantly to 0.03°C per second.
• The average melting point for stearic acid was approximately 52.8°C.
• The steepest part of the graph occurred between 0 and 4 minutes, indicating rapid cooling during this period.
• Between 5 and 10 minutes, the temperature leveled off, signifying the transition from liquid to solid with minimal heat loss.
• Starting from the 11th minute, the temperature exhibited a steady decrease, indicating the formation of solid bonds as the substance approached its freezing point.

Paraffin Wax:

• During the first 3 minutes, the paraffin wax was in the liquid phase, showing a cooling rate of 0.14°C per second.
• At the 9th minute, the paraffin wax underwent a phase change from liquid to solid.
• Similar to stearic acid, the cooling rate during solidification decreased to 0.03°C per second.
• The average melting point for paraffin wax was approximately 56.8°C.
• Between 0 and 4 minutes, the steepest part of the graph indicated rapid cooling for paraffin wax.
• Between 5 and 8 minutes, the temperature plateaued, indicating the transition from liquid to solid with minimal temperature change.
• Starting from the 9th minute, the temperature decreased steadily, signifying the formation of solid bonds as the substance approached its freezing point.

As substances are heated, their particles gain kinetic energy, resulting in increased motion and frequent collisions.

During melting, intermolecular bonds are broken, allowing for greater molecular movement and a shift from a solid to a liquid state. Heat energy is released during this process. Cooling, on the other hand, leads to the reformation of intermolecular bonds, accompanied by the release of heat energy. As the substance cools, its energy content decreases, leading to a decrease in particle movement.

Greater surface area during cooling enhances the rate of cooling. A larger surface area allows for more efficient heat dissipation, resulting in faster cooling, the faster formation of bonds, and quicker heat release.

Comparison to Published Values

Our class average for the melting point of stearic acid was 52°C, which is slightly below the published range of 55-70°C. The lower average may be attributed to possible anomalous results and variations in the timing of experiments among the students.

For paraffin wax, our class average was 50.7°C, falling within the published range of 46-68°C. This suggests that our class conducted the practical with a high degree of accuracy, achieving results that closely matched the published values. My personal melting point average for paraffin wax was 55-57°C, aligning well with the class average and indicating the absence of anomalies in my experiment.

States of Matter During Cooling Curves

Liquid Phase:

In the liquid phase, particles exhibit an absence of a regular arrangement, allowing them to flow and fit into available spaces while maintaining close proximity. Liquid particles cannot be compressed. They adapt to the shape of the container they are placed in, such as the test tube. In this phase, particles possess significant kinetic energy, facilitating rapid movement. Intermolecular bonds are not present during the liquid phase, as they were disrupted during the transition from the solid phase.

Solid Phase:

During the solid phase, particles undergo a transition to a fixed position, where they vibrate about their respective equilibrium points. Solids cannot be compressed, and their shape remains constant. Particles in the solid phase possess lower kinetic energy, which is utilized to form intermolecular bonds. This process also results in the release of heat energy.

Accuracy and Error Analysis

Random Errors:

• During both the calibration and cooling curve experiments, random errors could occur when the thermometer came into contact with the edges or bottom of the containers, leading to variations in temperature readings due to differing temperatures at these points.
• Parallax errors may have affected the accuracy of temperature readings if they were not taken at eye level, introducing potential inaccuracies and invalid results.

Systematic Errors:

We faced systematic errors during our experiments:

• During the calibration process, we ran out of time to complete the practical portion, leading to the use of an uncalibrated thermometer on the following day. This change in thermometers could have introduced errors as we were unsure if the new thermometer provided accurate results.
• The digital thermometer, which was not calibrated the following day, may have produced inaccurate results for the paraffin wax experiment, further compromising data accuracy.

Choice of Thermometer

For the cooling curve experiment, I selected the digital thermometer due to its ease of use and its ability to provide temperature readings with decimal precision. This decimal accuracy makes it a more reliable choice. I refrained from using the liquid thermometer due to its associated risks, such as parallax errors and the lack of decimal readings. The absence of decimal readings in the liquid thermometer would result in rounded values, potentially leading to less precise measurements.

Relative Error Calculation

The digital thermometer used in the experiment provided temperature readings rounded to the nearest decimal place (0.1°C), which could introduce relative errors. To determine the relative error, I will calculate the range of temperature values for one of my results, specifically the final reading for stearic acid.

Lowest reading for stearic acid: 33.9°C

Range: ±0.05°C (rounded to the nearest 0.1°C)

Temperature = 33.9 ± 0.05°C

Absolute error = 0.05°C

Relative error = (0.05°C / 33.9°C) * 100 = 0.1475%

Percentage error = 0.15%

Discussion

The conducted experiments involving thermometer calibration and cooling curve analysis have provided valuable insights into the behavior of substances during phase changes and the importance of accurate temperature measurements. Through the calibration process, we established the accuracy of our thermometers, allowing us to make informed decisions regarding their suitability for subsequent experiments.

In the cooling curve experiment, both stearic acid and paraffin wax underwent phase transitions from a liquid to a solid state. During the initial liquid phase, particles exhibited high kinetic energy, allowing them to move freely and adapt to the container's shape. However, as the substances cooled and transitioned into the solid phase, particles gradually assumed fixed positions and vibrated around their equilibrium points. This transition was accompanied by the release of heat energy.

Analysis of the cooling curves revealed distinct patterns. Stearic acid exhibited a rapid cooling rate during the first 4 minutes in its liquid phase, followed by a gradual decline in temperature. At the 11th minute, it transitioned into a solid state. Paraffin wax displayed a similar pattern, with a rapid cooling rate in its liquid phase for the initial 3 minutes, followed by a plateau in temperature. The solidification phase began at the 9th minute. These observations highlight the different cooling behaviors of the two substances, likely influenced by variations in their molecular structures.

Comparing our results to published values revealed some discrepancies. The class average for the melting point of stearic acid was 52°C, slightly lower than the published range of 55-70°C. This divergence may be attributed to random errors, variations in experimental timing, or anomalies. In contrast, the class average for paraffin wax was 50.7°C, falling within the published range of 46-68°C, suggesting a higher degree of accuracy in our experiments. My personal melting point average for paraffin wax, falling between 55-57°C, aligned well with the class average, indicating the absence of anomalies in my experiment.

Random errors, such as thermometer contact with container edges or parallax errors, posed challenges to data accuracy. Systematic errors emerged from changes in equipment and insufficient time for calibration, impacting the reliability of our results. These errors underscore the importance of meticulous experimental planning and adherence to calibration procedures to minimize inaccuracies.

Conclusion

In conclusion, the thermometer calibration and cooling curve experiments provided valuable insights into the behavior of substances during phase changes and the significance of accurate temperature measurements. The liquid-to-solid transitions observed in stearic acid and paraffin wax underscored the impact of intermolecular forces on the cooling process. The different cooling behaviors of these substances were influenced by variations in their molecular structures.

Our results, while generally accurate, demonstrated the presence of random and systematic errors that can affect the reliability of scientific data. Factors such as thermometer contact with container edges, parallax errors, and changes in equipment can introduce inaccuracies. Therefore, meticulous attention to experimental details, including proper calibration procedures, is essential for obtaining precise and reliable results.

These experiments have enhanced our understanding of temperature measurement and phase changes in substances, highlighting the importance of careful experimentation in scientific research.