Distillation of Simulated Crude Oil
This lab will require you to put together a distillation apparatus for each group of students. This will include a hotplate, an Erlenmeyer flask, two hole stopper, glass tubing, vinyl tubing, a condensation apparatus, and a small beakers to collect the condensate.
You will also have to mix up some simulated crude oil. This can be done by making a mixture of 20% methanol, 40% water, and 40% glycerin with a bit of calcium carbonate and a water-soluble black dye to make it look like oil. These are easily distilled since they have different boiling points. Just like in the fractional distillation of crude oil the temperature of the mixture rises and the different substances boil off at different temperatures. The condensation apparatus will then take the vapor and condense it back into a liquid.
Have students set up the distillation equipment and place a measured volume of the crude oil in the Erlenmeyer flask. The students need to distill this at medium heat to keep the liquid boiling slowly at all times during the distillation. Students collect three fractions during the distillation. The first fraction is collected from the starting point till the temperature reaches around 90 oC, since methanol boils at about 65 oC. The second fraction should be collected from the end point of the first until the temperature reaches 102 oC, since water boils at 100 oC. Once the fraction is collected at 102 oC, you will need to have the students turn off the hotplate and use the flask as the last fraction, since the glycerin boils at 290 oC. Be sure to allow the third fraction to cool thoroughly since it will be extremely hot! This distillation takes only about 20 minutes and it is very engaging for the students.
To analyze the fractions, you could do a number of things. A forensics twist to this is that you can make up molecular models of each of the three constituents in the mixture and have students identify them and their properties. You can then have the students determine the density of each of the fractions and then they have to identify which fraction is made up of the constituent and why, justifying their answers with such things as boiling points, densities, etc. You can even do some chemical testing, if you want to get even more involved with this lab.
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