Quarter 4 Lab Practical - Melting Point Determination

7) Melting Point Test - This page will walk you through the virtual process of taking the melting point of your sample.

Figure 1.

Background: One way to determine the melting point of a chemical is to put a small sample of the sample in a glass capillary (a tiny glass tube the size of a toothpick), strap the sample to a thermometer using a tiny rubber ring, and immerse the thermometer bulb and capillary sample into oil (see picture).

Then, the oil is slowly heated and the hot oil heats up the sample.

When the sample melts, you read the temperature on the thermometer and that will tell you the melting point.

Since the sample is usually very small and hard to see, most melting point apparatuses have a magnifying lens to help you watch the sample melt from solid to liquid.

Figure 1 shows a picture of the oil bath melting point apparatus.

Figure 2 below shows a picture of the magnifying lens view of the sample in the capillary tube.

Figure 2.

Step 1) Watch this video overview on the process of setting up a oil bath capillary melting point apparatus.

Step 2) Now watch the video excerpt below which focuses in on the process of finding the melting point of an example substance, benzoic acid, which melts at 122 degrees Celsius. This will give you a virtual experience of watching the sample in the capillary tube through the magnifying window as it goes through the process of melting.

Step 3) Finally, use this online melting point simulation to determine the melting point of your unknown A, B, C, or D (note that the simulation shows the samples as brightly colored but in nature they would actually be white crytalline solids).