1. to investigate the heating process for solid dodecanoic acid 2. to investigate the cooling process for liquid dodecanoic acid 3. to determine and compare the melting and freezing points of dodecanoic acid
test tube (18mm * 150 mm)
assembly (half full with solid dodecanoic acid with thermometer embedded) beaker (400 mL)
thermometer for water bath
dodecanoic acid, C11H23COOH (in test tube apparatus)
Part I: The Heating Process
We need to put on the lab apron and safety goggles before we do anything. Then we need to choose a partner and decide what role we are performing in Part I. One of us needs to be an observer, and the other will be the recorder. Later we will change our roles in Part II. The recorder need to record the temperature so then we can right the data in table I. while doing the lab, we need to obtain a test tube assembly consisting of a thermometer embedded in solid dodecanoic acid from Mr. Morrison. We need to remove the cotton plug and save it for the end of the lab. To do the lab, we need to put 300 mL of tap water into a 400 mL beaker and place the beaker on the hot plate. Then we need to turn the hot plate on to high heat and raise the temperature to around 55C to 60C, and we can measure the water temperature by using a thermometer. While the water is heating, we need to set up a ring stand with a buret clamp to hold the test tube assembly. When the water has reached to 55C, we need to turn the hot plate to a low heat. Then, we will lower the test tube assembly into the water bath and clamp in position so that all the dodecanoic acid is submerged below the water line. After that, the recorder can record the temperature of the dodecanoic acid in Table1, and every 30 s after that. During the heating process, the temperature of the water bath should be monitored with its thermometer to make certain that the water temperature remains above 55C. We should continue to record the temperature every 30 s, until a temperature above 50C is reached for the dodecanoic acid. As the dodecanoic acid melts, we need to stir it gently to mix the solid and liquid. Then the recorder will record the times when melting begins and ends. The observer will record the observations. After we've done all these, we need to turn off the hot plate and move quickly to Part II.
Part II: The Cooling Process
We and our partner can exchange roles during part II, and we can use table I to record the results from part II. After we've done part I, we need to raise the test tube assembly out of the hot water and clamp it in position in a room temperature water bath. So we can just replace the hot water in the beaker with room temperature water. After this, we need to start monitoring the cooling process immediately and record the temperature of the liquid dodecanoic acid. We need to record it for every 30 s until a temperature near 25C is attained. Then We will record when solidification begins and ends. The observer will record the observations at the same time. When a temperature at or near 25C has been attained, we may stop recording temperature readings. Right after this, we can reseal the test tube assembly with the cotton plug and return it to Mr. Morrison and put away all our equipments. Before leaving the laboratory, we need to wash our hands thoroughly with soap and water.
The test tube assembly containing the solidified dodecanoic acid with embedded thermometer is to be stored for future use.
POST LAB CONSIDERATIONS:
The results you have collected can now be analyzed with graphs that will represent the heating the cooling curves of dodecanoic acid.
Table 1 Heating and Cooling of Dodecanoic Acid
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