Melting Point Determination using Thomas Hoover Apparatus

• To determine the melting point of certain compounds using the Thomas-Hoover melting

point apparatus.• To assess the purity of these compounds.

01-10-14 and 01-17-14

Objectives

• Brief statement of objectives.. ala ku manual ):

Theoretical Background

Melting

Phase change from solid to

liquid

Melting Range

Kinetic Molecular

Theory

defined as

occurs within agoverned by

Theoretical BackgroundM

eltin

g Ra

nge Molecular

Structure

Intermolecular Forces

Purity of Solids

affected by

Data and Results

• Insert PAULO’s graph

Unknown no. 2 (119-124 ° C)

From the graph, we have where y is the temperature x & k is the knob settingWe obtain,

Unknown no. 5 (132- 137° C)

From the graph, we have where y is the temperature x & k is the knob settingWe obtain,

Unknown no. 2 (119-124 ° C)

• Trial 1Melt Start Temp.=122.0° CMelt End Temp.=123.0° C• Trial 2Melt Start Temp.=121.0° CMelt End Temp.=123.0° C

Unknown no. 5 (132- 137° C)

• Trial 1Melt Start Temp.=134.0° CMelt End Temp.=135.5° C• Trial 2Melt Start Temp.=134.0° CMelt End Temp.=136.0° C

Discussion and Analysis

• Noted Physical Appearance and Visual Properties of Unknowns– Unknown 2. =– Unknown 5. =

Discussion and Analysis

• Having calculated the optimum knob value based from the provided melting point range and the heating curve calibration, two trials for each unknown samples were performed.

• For the first unknown, the maximum range where the melting process was observed falls within 2 degrees Celsius as shown by the second trial (121-123) with the first trial showing only a range of 1 degree (122-123). In the aforementioned discussion of purity as based from the melting point range, where pure substances have a melting point range of 1-2 degrees Celsius, it can be deduced that Unknown 2. is a pure substance that has a melting of 121-123 degrees Celsius.

Discussion and Analysis

• The second unknown is found to have a different melting point but similar melting point ranges to the first unknown, which are at 1.5 and 2 degrees Celsius for the first and second trial respectively. Using the same deductions from the previous unknown substance, it is also determined that Unknown 5. is also a pure substance but with a higher melting point of 134-136 degrees Celsius.

• Further, combining these melting point ranges with their physical appearances and visual properties, we can trace the identity of both unknowns as (insert Unknown Identities here)

Conclusions

Molecular Structure

Molecular Symmetry

Size of Molecule

Packing

Intermolecular Forces

H-bonding

Dipole-dipole

London Dispersion

Purity of solids

Pure 1-2 degrees C

Impure > 1-2 degrees C