Physics – 2.1.2 Particle model | e-Consult

Answer: Experiment: Investigating the effect of intermolecular forces on melting point.

Apparatus:

• Three different substances with varying intermolecular forces (e.g., wax, salt, sugar).
• Three identical calorimeters (e.g., polystyrene cups nested within each other).
• Thermometer
• Hot plate or Bunsen burner
• Stopwatch
• Beakers
• Measuring cylinders

Procedure:

1. Measure a specific mass of each substance (e.g., 5g) and place it in a separate beaker.
2. Place the beaker containing each substance inside a calorimeter.
3. Add a known volume of water to each calorimeter (e.g., 50 cm³). This ensures the temperature change is due to the substance melting, not the water.
4. Place the calorimeter on a hot plate or carefully heat it with a Bunsen burner.
5. Monitor the temperature of the water in the calorimeter using the thermometer.
6. Record the time taken for each substance to completely melt.
7. Repeat the experiment at least three times for each substance to improve accuracy.

Analysis:

1. Calculate the average melting point for each substance from the recorded data.
2. Compare the average melting points of the three substances.
3. Plot a graph of melting point versus the estimated strength of intermolecular forces (e.g., using a qualitative scale: weak, moderate, strong). This would require prior knowledge of the types of intermolecular forces present in each substance.
4. Discuss the relationship between the strength of intermolecular forces and the melting point. Substances with stronger intermolecular forces will have higher melting points.