Today, we conducted a lab on the heating and cooling curves of a pure substance. For this lab, our objective was to determine, while comparing the melting and freezing points of a pure substance; dodecanoic acid.
First of all, we read through the lab and made sure we knew what we were doing. Then, in the beginning of the lab, we put on some safety equipment to prevent the impossible from being possible. The chemical’s that we worked was not a very strong acid, so it wasn’t a big threat to our safety.
We started the cooling process of the dodecanoic acid before starting the heating process. The cooling process took a bit of time, but the process was simple. First, we filled a beaker that had room temperature water. Then, we clamped a test tube that contained the acid. We attached it to the ring stand, placing the test tube inside the room temperature water. After doing so, we observed the temperature of the acid. Every 30 seconds, we used a thermometer to record the temperature of the acid, until it is near 25 degrees Celsius. Also, note when solidification beings and ends, and any other observations you see.
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| This picture includes a ring stand, clamp, test tube and thermometer. |
Right after finishing the cooling process, we began the heating process! WOOO!! Similarly, we put the test tube (with the solidified acid inside) in water, and kept it hot with a hot plate. Until a temperature of 50 degree Celsius (or above) is achieved, you record the temperature every 30 seconds; while noting down any other observations. When the acid melts, you mix the solid and liquid together, then record when the melting began and ended.
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| This is a hot plate! Be Careful! Don't burn yourself!! |
After, you put away the equipment and return the test tube to your instructor. After, you wash your hands thoroughly with soap! Last but not least, you do a lab report, and after completing it, you would have already compared the melting and cooling curves of a pure substance.
http://www.dillpickletheater.com/REMSL/index.htm
http://www.enotes.com/earth-science/freezing-melting
This video may also somewhat assist you with your understanding of melting and freezing points:
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