Chem 206-3 - In the first part there were four samples in...

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In the first part, there were four samples in each bench. In the hood number nine, the samples whose melting points would be determined were cinnamic acid (C 9 H 8 O 2 ), purified naphtalene (C 10 H 8 ) in the experiement 2, cinnamic acid(C 9 H 8 O 2 )-urea((NH 2 ) 2 CO) (75:25) mixture and an unknown numbered 3. First all of those chemicals which have crystalline structures were crushed then placed into capillary tubes. Then all of them were stick next to a thermometer and put into Thiele tube which was heated one by one. First the one whose melting point was expected to be the lowest was put into the set up, then others’ melting points were measured gradually. When the solids started to melt temperature was recorded, as soon as all of the material in the tube melted temperature was recorded again . For naphthalene, unknown mixture and cinnamic acid’s melting point range were found to be 68.0-70.0 0 C, 72-75 0 C ,105- 105 0 C and 130.0- 135.0 0 C, respectively. In the second part, pure naphthalene’s melting point was determined using a melting point apparatus. The result was found to be 81.0-83.0 0 C. This result was compared to the result found in the first part and the melting point of naphtalene in the literature. INTRODUCTION: The aim of this experiment is to determine the melting temperatures of different chemicals both compounds and mixtures using two different methods. Melting is the phase change from solid to liquid in any material. Melting point is the temperature at which melting occurs. While pure crystalline substances have sharp melting points, ranges are defined in melting point determination of mixtures. 1
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Knowing melting point of a substance helps to guess physical characteristics of that substance especially the purity. The effects in determination of melting point temperature are the molecule, symmetry and bonding type. Bigger molecules have higher melting points compared to smaller molecules. Symmetric molecules have higher melting points compared to asymmetric ones. The number of H-bonding in a molecule increases the melting point. Two methods were applied in this experiment to find out the melting points or ranges. First was Thiele method. In this method, powdered samples are put into capillary tubes, those tubes are attached to thermometers and and placed into Thiele tubes which contains silicone oil in it. Heat is given to the system and melting is waited to be observed. Starting temperature and end
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Chem 206-3 - In the first part there were four samples in...

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