Study on Paraffin Wax and Stearic Acid Cooling Curve

Abstract

The objective of this experiment was to investigate the cooling behavior of two substances, stearic acid and paraffin wax, and to construct cooling curves for both materials. To ensure the accuracy of our data, we employed calibrated thermometers. This study provides insights into the cooling kinetics of these substances, which can be valuable in various industrial and scientific applications.

Introduction

Cooling curves are essential tools in understanding the phase transition of materials as they change from a liquid to a solid state.

The rate of cooling during this transition can reveal valuable information about the substance's physical properties and behavior. In this experiment, we aimed to investigate and compare the cooling curves of stearic acid and paraffin wax. To maintain data accuracy, we calibrated our thermometers and employed consistent experimental conditions.

Methodology

Calibrating Thermometers

Prior to the experiment, it was crucial to calibrate the thermometers to ensure accurate temperature measurements. Liquid-filled mercury thermometers were chosen for their rapid response to temperature changes and their reliability.

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Materials and Equipment

• Hot water (boiling)
• Ice
• Digital thermometer
• Liquid-filled mercury thermometer
• Timer
• Beaker (250cm³)
• Boiling tube
• Stearic acid
• Paraffin wax
• Stopwatch
• Test tube rack
• Thermometer

Health and Safety Requirements

• Wear lab coats to prevent stains on clothes.
• Notify the instructor of any damaged equipment.
• Wear goggles to protect your eyes.
• Use gloves and lab coats to prevent cuts and scratches from glass materials.

Stearic Acid Experiment

1. Place 50ml of stearic acid in a boiling tube and heat it in a water bath until it becomes a liquid and reaches the temperature of hot boiling water.

2. Remove the boiling tube from the water bath and place it on a test tube rack.

3. Insert a thermometer into the center of the boiling tube containing stearic acid.

4. Record the temperature every 30 seconds until the stearic acid reaches room temperature.

Paraffin Wax Experiment

1. Place 50ml of paraffin wax in a boiling tube and heat it in a water bath until it becomes a liquid and reaches the temperature of hot boiling water.

2. Remove the boiling tube from the water bath and place it on a test tube rack.

3. Insert a thermometer into the center of the boiling tube containing paraffin wax.

4. Record the temperature every 30 seconds until the paraffin wax reaches room temperature.

Results

Calibration of Liquid (Mercury) Thermometer in Ice Water

Calibration of Liquid (Mercury) Thermometer in Boiling Water

Calibration of Digital Thermometer in Ice Water

Calibration of Digital Thermometer in Boiling Water

Analysis of Cooling Curve

The rate of cooling for both stearic acid and paraffin wax initially showed rapid temperature decline, indicating a significant drop in thermal energy. The cooling curves displayed plateaus, which correspond to the melting points of the substances. During this phase, no change in temperature was observed, indicating an exothermic process where thermal energy was lost to the surroundings, balancing the energy released during bond formation.

The rate of cooling is influenced by intermolecular forces and changes in state, as substances transition between solid and liquid phases. The strength of intermolecular forces and the kinetic energy of molecules play pivotal roles in determining a substance's physical state and its melting point. Stronger intermolecular forces require higher thermal energy to break the attractive forces between molecules, resulting in a higher melting point. Consequently, a decrease in temperature leads to decreased kinetic energy, causing molecules to form solid bonds. This experiment utilized these principles to determine the rate of cooling for stearic acid and paraffin wax, as reflected in the accurately drawn gradients.

Conclusion

The primary objective of investigating the rate of cooling for stearic acid and paraffin wax, using calibrated thermometers to ensure data accuracy and constructing structured cooling curves, was successfully achieved. To maintain fairness and accuracy in the experiment, the same thermometer, boiling tube, and hot water bath were used for both substances.

Areas for Improvement

Enhancements in precision could be achieved by minimizing factors that affect room temperature and through improved planning and execution, ultimately leading to more accurate results.