Melting and freezing stearic acid Class practical In this class practical students take the temperatureof stearic acidat regular intervals as they heatand coolit. They can observe the meltingand freezing pointsof the acid and can plot a graph. This experiment could also be done using data- loggingequipment. Lesson organisation This practical takes quite a long time to carry out. Students can begin by simply recording their data but, once they get the hang of what they are doing, most should be able to plot the graph at the same time as taking readings. If data-loggers are being used then students will need another activity to be doing alongside the experiment. Apparatus Chemicals Eye protection Per pair orgroup ofstudents:Beaker (250 cm 3 ) Boiling tube (Note 1) Thermometer (0-100C) Stop clock Clamp, stand and boss Bunsen burner Tripod Gauze Heat resistant mat Stearic acid(octadecanoic acid) Refer to Health & Safety and Technical notes section below for additional information. Health & Safety and Technical notes Read our standard health & safety guidance Wear eye protection. Stearic acid(octadecanoic acid), CH 3 (CH 2 ) 16 COOH(s) - see CLEAPSS Hazcard. The stearic acid in this practical can be used again and again. Have enough to ¼ fill a boiling tube for each student 1If, after the practical, the boiling tubes are left containing both the stearic acidand the thermometer, immerse all the boiling tubes in hot water to remove the thermometers. The stearic acidcan then be stored in the boiling tubes and recycled several times. Unit 2. Particles and Atomic Structure Syllabus Ref. 1
