Essay Liquids and Solids Lab Report

Background

Pure crystalline solid compounds have accurate melting point, at which the compound switches from the solid to liquid states. For small samples, the transition time and the temperature are small. The melting point of pure samples is a useful physical attribute to identify a sample (Armarego & Chai, 2012). The process of transformation of crystalline solids to liquid is reversible. Different compounds have different melting points. Impure compounds melt at temperatures less the melting points of pure solids. On the other hand, when liquids are heated, they finally reach a point where the vapor pressure is large that forms bubbles inside the liquid. The boiling temperature remains constant until all the liquid converts to a gaseous state after heating a liquid. Different liquids have different boiling points. Boiling points of liquids are useful in the determination of purity. Theoretically, it is not possible to heat a liquid beyond its normal boiling point (Valderama et al., 2012).

The purpose of the experiment

The purpose of the experiment was to determine the boiling point of isopropyl alcohol. The second objective was to determine the melting point of powdered acetamide.

Procedure

Experiment 1: Measurement of boiling point of Isopropyl alcohol

About 1ml of isopropyl alcohol was placed in a test tube. Using a small band, a thermometer was attached to the outer surface of the test tube, with the thermometer bulb even to the bottom of the test tube. An inverted closed end capillarity tube was inserted to the test tube. The second part of the 100ml beaker was half filled with warm tap water, and the test tube assembly was placed in the water bath. The surface level of the alcohol was beneath the surface level of the water bath. A burner stand was set up, and the beaker containing the assembly was placed on the top. The burner fuel was lit beneath the beaker whilst stirring frequently to ensure even heating. The water was heated rapidly until a steam of bubbles was observed emerging from the capillarity tube. The temperature was recorded after the emergence of the last bubble from the capillarity tube. The procedure was replicated thrice and the temperature readings recorded in Table 1.

Experiment 2: evaluation of the melting point

With gloved hands, powdered acetamide was inserted to the open end of the second capillarity tube, by gently tapping the powder into the tube. The tapping was repeated severally till the powdered acetamide moved at least three quarters towards the closed end of the capillarity tube, occupying 1-2mm of the capillarity tube end. Using a rubber band, the capillarity tube was attached to a thermometer such that the bulb of the thermometer aligns to the end of the capillarity tube. 100ml beaker was half filled with warm tap water, and the test tube assembly was placed in the water bath. The surface level of the acetamide was beneath the surface level of the water bath. A burner stand was set up, and the beaker containing the assembly was placed on the top. The burner fuel was lit beneath the beaker whilst observing the acetamide. The melting temperature was recorded, and the burner flame immediately extinguish to allow the acetamide to cool and re-crystallize. The process was replicated thrice and the results recorded in Table 2.

Results

Table 1: boiling point temperature readings for Isopropyl alcohol

Experiment1: boiling point	Reading 1	Reading 2	Reading 3	Final reading
Temperature (degrees Celsius)	82.5	82.6	82.8	82.6

Published boiling point of isopropyl alcohol: 82.4 degrees Celsius

Final reading from the experiment: 80.0 degrees Celsius

Therefore, the percentage error is 0.0024%

Table 2: Melting point readings for powdered acetamide

Experiment2: melting point	Reading 1	Reading 2	Reading 3	Final reading
Temperature (degrees Celsius)	80.0	79.6	80.4	80.0

Published melting point of acetamide: 81.0 degrees Celsius

Final reading from the experiment: 80.0 degrees Celsius

Therefore, the percentage error is 1.24%

Answers to Questions

A) The melting point of compound designates the degree of purity. Compounds have well defined melting points. On the other hand, liquids have defined boiling points, which also specify the purity of the liquid. The melting points and the boiling points are a characteristic physical property.
B) The melting point is determined by heating the substance in a special melting point apparatus. It is possible to monitor the temperature as it rises, using a digital thermometer. Due to the high heat required to heat the compound, a range of the temperature will be recorded. This will occur from the start of melting of the substance, to the final temperature when the compound melts entirely (Haynes et al., 2012). Some compounds melt at just about 400 degrees Celsius temperature.
C) Increasing the number of crystals affects the melting point range. This is because melting of compounds do not occur instantaneously, as the molecules of a compound melts when they acquire energy. Therefore, melting will start from the crystals in contact with heat, an as it progresses towards inner crystals.
D) Sources of error
i) Contamination of the powdered acetamide
ii) Faulty thermometer

iii) Unsterilized equipments such as the capillary tubes.

Conclusion

The experiments were conducted successfully following all the procedures and safety measures. It is clear from the experiments that liquids have specific boiling points. It was apparent that crystalline solids have specific melting points. The data collected had a small error margin compared to the published melting point and the boiling points was minimal at 0.0024% and 1.24% respectively for the 2 experiments.

References

Armarego, W. L., & Chai, C. (2012). Purification of lab chemicals and solutions. Butterwolth Heineman.

Haynes, W. M., Lide, D. R., & Bruno, T. J. (Eds.). (2012). CRC Handbook of Chemistry and Physics 2012. CRC press.

Valderrama, J. O., Forero, L. A., & Rojas, R. E. (2012). Critical properties and normal boiling temperatures of ionic liquid. Update and a new reliability test. Industrial Chemistry Research, 51(22), 7838-7844.