States of Matter : Phase Change

Investigate how temperature changes when a pure substance melts or freezes. Determine the melting point and the freezing point for an unknown pure substance, and use that information to determine the most probable identity of the substance.

Lab Summary:

In this activity, students will use a temperature sensor to measure temperature changes at regular time intervals as a solid substance slowly melts and then re-solidifies. From these time-temperature readings they will determine the melting point and freezing point of the solid. They will describe what happens to the temperature during the phase change from the time melting or freezing first begins until the process is complete.

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(student version)

Method:

Use the Temperature Sensor to measure temperature changes at regular time intervals as a solid substance slowly melts and then resolidifies. Determine the melting point and freezing point of the solid.

Here's What You Need:

Probeware

• PASPORT Temperature Sensor (PS-2125)
• Xplorer GLX Graphing Datalogger (PS-2002)
  (or alternate PASPORT interface -- see other options)

Other Materials

• Small Tripod Base & Rod (SE-9451)
• Buret Clamp (SE-9446)
• Hot plate
• Beaker, 250-mL
• Test tube, medium
• Water
• Unknown pure substance (e.g., lauric acid, thymol, p-dichlorobenzene)

Lab Manual:

This activity is included in Explorations in Chemistry (PS-2808), complete with Teacher Information pages, student instructions and handouts, and sample data for a total of 25 probeware-based labs. For your convenience, we offer bundles which provide the probeware necessary for the activities in the manual. For more information on these resources and bundles, click here.