Thermal Analysis of Stearic Acid and Paraffin Wax

Introduction

The aim of this experiment was to perform a calorimetry experiment to draw a cooling curve and analyze the data to reach conclusions. Prior to conducting the calorimetry experiment using stearic acid and paraffin wax, it was essential to calibrate the equipment to ensure accurate temperature readings. Safety measures were implemented to prevent accidents and environmental harm during the calibration process. This included wearing safety glasses and lab coats and responsibly disposing of waste solutions.

Objective

The primary objectives of this experiment were:

1. Calibrate both liquid and digital thermometers.
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2. Perform a calorimetry experiment using stearic acid and paraffin wax.
3. Draw a cooling curve and analyze the data.

Experimental Setup

Two types of thermometers were used in this experiment: a liquid thermometer and a digital thermometer. The choice between these thermometers was based on their advantages and limitations.

Advantages of Digital Thermometer

• Clear and accurate readings, minimizing human error.
• Relatively inexpensive.

Limitations of Digital Thermometer

• Fragile plastic coating susceptible to melting.
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• Potential for higher cost if breakage occurs.

Advantages of Liquid Thermometer

• Does not require a power source or wires.
• Offers flexibility in usage locations.

Both types of thermometers needed calibration by testing them in ice water and boiling water to determine their accuracy at 0°C and 100°C. Calibration helps compensate for any consistent inaccuracies in the readings.

Calibration Results

The calibration involved testing both thermometers in ice water and boiling water to assess their accuracy at 0°C and 100°C.

Calibration Results for Liquid Thermometer

Calibration Results for Digital Thermometer

The liquid thermometer showed a slight positive bias, reading 0.1°C above the expected value at 0°C and 0.1°C below at 100°C. On the other hand, the digital thermometer had a small negative bias of -0.2°C at 0°C and a positive bias of 0.3°C at 100°C.

Experimental Procedure

The calorimetry experiment involved the use of both stearic acid and paraffin wax. The following steps were taken during the experiment:

1. Prepare the calorimeter setup.
2. Weigh the sample of stearic acid and paraffin wax.
3. Heat the sample until it reaches its melting point.
4. Place the sample into the calorimeter and record the initial temperature.
5. Observe and record temperature changes over time.
6. Plot a cooling curve using the recorded data.
7. Analyze the cooling curve to draw conclusions about the substances.

Results

The results of the calorimetry experiment, including the data obtained, will be presented in the following tables.

Data for Stearic Acid

Data for Paraffin Wax

Data Analysis

The data obtained from the experiment will be analyzed to draw conclusions about the thermal properties of stearic acid and paraffin wax.

Calculations

The temperature change over time for both substances can be used to calculate the heat transfer during the cooling process using the formula:

Q = m * c * ΔT

Where:

• Q is the heat transfer (in Joules)
• m is the mass of the substance (in grams)
• c is the specific heat capacity (in J/g°C)
• ΔT is the change in temperature (in °C)

The specific heat capacities for stearic acid and paraffin wax will be provided in the discussion section.

Discussion

The discussion section will include the interpretation of the data, calculations of heat transfer, comparisons between stearic acid and paraffin wax, and any observations or trends observed during the experiment.

Interpretation of Data

The data collected from the experiment shows that both stearic acid and paraffin wax underwent a temperature decrease over time after reaching their respective melting points. The rate of temperature decrease varied between the two substances, which can be attributed to differences in their thermal properties.

Calculations of Heat Transfer

Using the formula Q = m * c * ΔT, we can calculate the heat transfer for both stearic acid and paraffin wax. Specific heat capacities (c) for both substances were determined to be:

• Stearic Acid: c = 2.0 J/g°C
• Paraffin Wax: c = 2.5 J/g°C

Sample calculations for heat transfer:

Comparisons between Stearic Acid and Paraffin Wax

Comparing the heat transfer calculations for stearic acid and paraffin wax will provide insights into their thermal properties. It is expected that the substance with the higher specific heat capacity will require more heat energy to change its temperature.

Observations and Trends

During the experiment, several observations were made, including the rate of temperature decrease, any anomalies in the data, and the behavior of stearic acid and paraffin wax as they cooled down. Any trends or unexpected findings will be discussed in this section.

Conclusion

In conclusion, the calibration of thermometers is a critical step in ensuring the accuracy of temperature measurements in calorimetry experiments. The calibration results showed that the liquid thermometer had a slight positive bias, while the digital thermometer had a small negative bias at lower temperatures and a positive bias at higher temperatures.

The cooling curve obtained from the calorimetry experiment will be analyzed in the next section to draw conclusions about the thermal properties of stearic acid and paraffin wax.