Calorimetry in Industry and Thermodynamics: Experimental Analysis

Industry Applications of Calorimetry

Calorimetry finds widespread applications in various industries, with notable examples being food calorimetry within the food industry and bomb calorimetry in thermodynamics. In the food industry, calorimetry offers a precise method for determining the calorie content of different food types. This is achieved by using food samples as the fuel source and burning them to observe changes in temperature and mass. Bomb calorimetry, on the other hand, is employed to measure the heat of combustion for diverse organic materials.

It involves placing the material in a sealed container filled with oxygen, which is then combusted using a hot wire. In industries like pharmaceuticals, bomb calorimetry serves the critical purpose of safety testing materials sealed within containers.

Thermometer Calibration

The accuracy of temperature measurements in this experiment was ensured through proper calibration of the thermometers. To achieve this, the thermometers were immersed in a beaker containing ice and a small amount of water. Calibration was deemed successful once the temperature reached zero degrees Celsius.

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Both liquid and digital thermometers underwent calibration, demonstrating consistent results. They both initially started around the same temperature and exhibited rapid decreases upon immersion in the wax and acid, aligning closely in terms of their leveling over time.

Liquid Thermometer Calibration (Ice Water)

Digital Thermometer Calibration (Ice Water)

Method

The experimental method involved heating paraffin wax and stearic acid to their respective melting points and then using a calibrated thermometer to monitor the temperature as they cooled and solidified to room temperature.

Initially, the paraffin wax test tube was immersed in a beaker of hot water to facilitate the melting of the wax. Once the wax had melted, the test tube was carefully removed and suspended in the air using a clamp and stand. A previously calibrated thermometer, set to zero using ice and cold water, was employed to precisely measure the temperature at regular 30-second intervals as the wax solidified at room temperature. The recorded temperature data was then used to create a cooling curve for the wax. The same method was applied to stearic acid to ensure fair and comparable results.

Equipment Used

• Paraffin wax and stearic acid
• Test tubes to contain the substances
• Clamp and stand to suspend the test tubes
• Calibrated thermometer for temperature measurement
• Beaker of hot water for heating the test tubes and substances

Advantages and Disadvantages

Advantages

• Accurate temperature readings within the test tube at various time intervals.
• Automated data collection reduces the potential for human errors.

Disadvantages

• Heat loss to the surroundings during the experiment may affect the accuracy of temperature measurements.
• External factors such as open windows or fluctuations in ambient temperature (hot/cold weather) can introduce variability in the results.

Stearic Acid

What is it: Stearic acid is one of the many fatty acids found naturally in various plants and animal derivatives.

Formula: CH₃(CH₂)₁₆COOH

Paraffin Wax

What is it: Paraffin wax is a white or colorless, soft, solid derived from petroleum (coal or oil shale). It consists of a mixture of hydrocarbon molecules containing between twenty and forty carbon atoms.

Formula: C_nH_2n+2

Stearic Acid Results

The initial room temperature at the beginning of the experiment was 22°C.

The temperature at which stearic acid completely melted was 65°C, and the temperature at which it solidified was 55°C.

Gradient 1 = -0.04

Gradient 2 = 0

Gradient 3 = -0.02

Interpreting the Gradients

The recorded gradients provide valuable insights into the steepness of the temperature change during the experiment.

Gradient 1: The initial gradient of -0.04 indicates a rapid temperature decline at the beginning of the experiment. This steep slope is corroborated by the data in the table, which shows a substantial temperature drop from the initial 65°C at 0 seconds to the stabilized temperature of 51°C at 210 seconds.

Gradient 2: A gradient of 0 signifies that the rate of cooling remains constant. This is evident from the temperature data, where there is no discernible increase or decrease in temperature between 330 seconds and 1440 seconds (24 minutes).

Gradient 3: This gradient indicates a change in temperature from the midpoint reached earlier in the experiment. The table's results demonstrate a consistent decrease in temperature over time as the substance continues to cool.

In terms of the experiment, these gradients confirm that the procedure was carried out accurately and successfully.

Paraffin Wax

The initial room temperature at the beginning of the experiment was 21°C.

The temperature at which paraffin wax completely melted was 37°C, and the temperature at which it solidified was 37°C as well.

Gradient 1 = -0.02

Gradient 2 = -0.005

Gradient 3 = -0.015

Interpreting the Gradients

Gradient 1: A result of -0.02 indicates a consistent and rapid decrease in temperature in the early stages of the experiment. This is corroborated by the data in the table, which illustrates a significant drop in temperature from 63°C to 56°C within the first 30 seconds of the experiment.

Gradient 2: A gradient of -0.005 suggests that the graph does not reach a plateau but experiences a slow temperature decline over an extended period in the middle of the results.

Gradient 3: With a value of -0.015, Gradient 3 indicates that the stearic acid has passed the midpoint of the experiment, resuming a steady temperature decrease akin to the rate observed in Gradient 1.

These gradient analyses affirm the correct execution of the experiment and provide a basis for comparison with the results obtained from the paraffin wax experiment.

Stearic Acid Analysis

• Both the paraffin wax and stearic acid experiments exhibit discernible patterns and trends. They both commence at elevated temperatures, such as 63°C for stearic acid and 65°C for paraffin wax, before undergoing a rapid initial decrease. Subsequently, they reach a plateau around 51/52°C, maintaining this temperature for an extended period. After a significant amount of time has elapsed, both substances resume a faster temperature decrease.
• Comparing my results to published data, I discovered cooling curve graphs from similar experiments conducted with accurate laboratory equipment. Although my graph is plotted in seconds, while the published data may use minutes, the cooling curves exhibit striking similarities. This confirms the accuracy of my experiment and the validity of my results.

Paraffin Wax Analysis

• Comparing the results of the paraffin wax experiment to those of the stearic acid experiment reveals some differences. Notably, the paraffin wax experiment exhibits an earlier onset of temperature decline and a longer cooling time compared to the stearic acid experiment.
• In contrast to stearic acid, the paraffin wax graph does not maintain a consistent temperature during a stationary phase but instead shows fluctuations. However, when comparing the cooling curves to published data, several similarities emerge. Both graphs share comparable shapes and display similarities in the recorded experiment times and the temperatures at which they stabilize.

Evaluation

Direct comparisons with published data for both substances are challenging due to several factors: unknown substance masses, differences in time scales, and computer-generated data plotting, which minimizes human error.

The changes in state can be explained by examining particle arrangement and the strength of intermolecular bonding. Solids have particles closely packed in layers with strong bonds, while liquids have particles that can move more freely but still maintain relatively strong bonds. Heating a solid increases particle movement until the bonds are broken, resulting in a change from a solid to a liquid state. Conversely, when heat energy is removed, the bonds reform, causing a change from a liquid back to a solid state.

Various factors could have influenced the rate of cooling for each substance. Not using a lid allowed for quicker cooling, but it might have resulted in faster cooling than desired. Using a smaller mass of each substance was necessary to expedite cooling, but using a larger mass over a longer time period might have yielded more precise data. Ensuring both experiments used the same-sized boiling tube maintained fairness, as a larger surface area would have led to faster cooling. Differences in ventilation and room temperatures during the experiments could have introduced variability. Using a digital thermometer, while accurate when calibrated, posed challenges due to fluctuating numbers, which required estimation. Repeating each test and taking an average or employing a temperature probe and data logger could have reduced human error. Allowing substances to cool fully to room temperature was ideal but was not possible due to time constraints, potentially impacting result accuracy.