Melting Point Lab Conclusion Essay

Melting Points
Elizabeth McGrail
Organic Chemistry I
25 January 2013

ABSTRACT
The objectives of this lab are, as follows; to understand what occurs at the molecular level when a substance melts; to understand the primary purpose of melting point data; to demonstrate the technique for obtaining the melting point of an organic substance; and to explain the effect of impurities on the melting point of a substance. Through the experimentation of three substances, tetracosane, 1-tetradecanol and a mixture of the two, observations can be made in reference to melting point concerning polarity, molecular weight and purity of the substance. When comparing the two substances, it is evident that heavy molecule weight of tetracosane allowed…show more content…

During the experiment, heating the water too quickly would create inaccurate data. If the water is heated too quickly, the thermometer may have a hard time keeping up with the temperate, thus displaying an inaccurate measurement. It would be must harder to obtain an accurate range, if this were the case, as the substance may melt faster than observable. A molecule’s melting point is reflective of its physical properties. Melting points disrupt intermolecular forces, spreading atoms over a greater surface area; melting points do not affect covalent bonds, thus are not chemical changes.

At the conclusion of this experiment, I have determined that the molecular weight of the given molecules played a greater role in determining its melting point. 1-tetradecanol, an alcohol, contains the functional group –OH. This type of bond is referred to as a Hydrogen bond; hydrogen bonds are much stronger than typical dipole-dipole bonds found in many ionic compounds. The molecular formula for tetracosane is C24H50. The molecule contains no functional group, so the intermolecular bonds are dispersion forces; the weakest bond noted between atoms. Given this information regarding polarity and the molecular weights of the compound, it is easy to conclude that the weight of the tetracosane caused it to have a higher melting point. CONCLUSION
At the conclusion of

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Melting Point Determination and Thermometer Calibration Lab

Background: The melting point of a substance, a solid in this case, signifies the temperature at which the first crystal starts to melt until the temperature at which the last crystal disappears is reached. That being said, melting points are expressed in ranges, am organic compound will have a sharp range depending on the purity of the compound. Impurity of an organic substance will register an abnormal melting point based on its expected propensity observed, this will cause the temperature range to widen. Using this hypothesis, mixed melting point technique could determine if the unknown compound added to the mixture causes a temperature depression, if not, the unknown is…show more content…

The mixture melting points were harder to be accurate with because there is no definite way to measure exactly the ratios needed of both compounds. Also, not mixing the compounds well enough and not getting an even mixture of the compounds in the capillary tubes may alter the results to be different from the lit values. The graph of the melting point ranges of the mixtures of urea/cinnamic acid (4:1, 2:1, 1:1, 1:2,1:4 ratios) enables us to find the Eutectic Point. The Eutectic Point is the lowest temperature at which a substance will melt. As for the unknowns, the two unknown numbers were #2 and #53. We found unknown #2 to be benzoic acid and unknown #53 to be salicylic acid. The melting points we measured matched these to lit values with an accuracy of +/- 1°C. The difficulty in finding the identity of the unknowns is being extremely careful only to raise the temperature by 1-2°C per minute. This is extremely important for finding all melting points because if this is not done the temperature will increase too rapidly and wrong melting points will result. This lab enables us to experimentally find the melting points of certain compounds and mixtures of compounds. If the temperature is raised too quickly, an innacurate melting will be taken. When compounds are mixed, this fluctuates the melting point and creates a symmetrical phase diagram as the one done in this experiment with urea and trans-cinnamic acid. We learned how to use the thiele tube

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