Temperature and Test Tube

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Freezing and Melting of Paradichlorobenzene

Melting, freezing, and boiling points are properties that can easily be determined and help in identifying a substance. These properties can be found in chemical literature ad reference tables, and can be used to distinguish a pure substance from many other pure substances. In this lab you will use the pure substance Paradichlorobenzene and determine its melting an freezing points by warming and cooling a sample of the substance, then plotting heating and cooling curves and analyzing them. Data that you collect will represent the heating and cooling behavior common to all pure substances.

List of Materials:
-Large Test Tube (18*15 mm) -Safety goggles-Paradichlorobenzene -Hot Plate -Lab Apron-Acetone
-Test Tube Holder -Ring Stand
-2 Thermometers -A Ring Clamp

1. Make a data table with headings for time, temperature of Paradichlorobenzene, and temperature of water. 2. Fill a 250mL beaker about 3/4th full of cool tap water. Place a thermometer in the beaker and record the temperature to the nearest 0.2C 3. Obtain a test tube containing solid Paradichlorobenzene from your teacher and gently heat the test tube over a medium Bunsen burner flame. Move the test tube in and out of the flame at a slight angle. 4. Once the Paradichlorobenzene has melted, remove it from the flame and shut the gas valve off. 5. Before moving on to part I, fill up another 250mL beaker 3/4th full of cool tap water and begin to heat up a hot plate on medium to high heat.

Part I - Cooling of Paradichlorobenzene
6. Put a thermometer into the test tube of melted Paradichlorobenzene. Record the temperature in your data table. 7. Lower the test tube into the beaker of water until all of the Paradichlorobenzene is under water. Fasten the clamp onto the ring stand. 8. Wait 30 seconds. During that time, stir the Paradichlorobenzene by...
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