Simulating The Refining of Petroleum 12/12 Integrated Science 3 Redwood High School Name : Per: Introduction Petroleum, or crude oil, is a complex mixture of substances. It is believed that crude oil is produced naturally from animal and vegetable matter at the bottoms of shallow seas and swamps. When tiny plants and animals die in the sea, they settle slowly to the bottom where they become trapped in mud and sand. As the layers of sediment become compressed over time, the sediment turns into rock. During this process some of the body tissue of the trapped organisms is changed into a viscous, sticky liquid called petroleum (crude oil). The petroleum is eventually squeezed out of the sediment in which it formed and spreads through porous rock layers like water in a sponge. Petroleum was first discovered where it seeped to the surface in shallow pools. People gradually learned that this raw material could be separated into substances that were more useful than the original crude mixture. Currently, refined petroleum is used to make items such as gasoline, asphalt, lubricants, kerosene, waxes and plastics. A commonly used technique for separating out the various substances found in petroleum (crude oil) is known as fractional distillation. See the diagram on the right. Fractional distillation separates the different components of crude oil using the physical property of boiling point. This separation is done by heating, evaporating, cooling and condensing the original crude mixture until you have separated out the different materials that make it up. Recall that boiling point is the temperature at which a liquid changes to a gas (vapor) at normal atmospheric pressure. Different substances have different boiling points. In this experiment, you will determine some properties of a mixture of liquids, simulating crude oil. You will then distill the mixture and examine the properties of the resulting fractions to see if you succeeded in separating the liquids that made up the original mixture.
Procedures Part 1. Determine Properties of the Crude Mixture 1. Complete the first column of Data Table 1, summarizing properties of the unknown crude mixture. A. Observe and record the appearance and odor of the crude mixture. B. Determine and record the mass (g) and volume (ml) of the fraction by completing the following: i. Using an electronic balance, determine the mass of an empty graduated cylinder. ii. Measure and pour 50ml of the crude mixture into the graduated cylinder - and then measure the mass of the graduated cylinder with the crude mixture. iii. Determine the mass of the fraction by taking the difference between the mass of the graduated cylinder with the fraction and the mass of the empty graduated cylinder. C. Calculate the density of the crude mixture using the following equation density = mass (g) / volume (ml) D. Test and record the flammability of the crude mixture by dipping a small piece of paper in the liquid and placing it in an evaporating dish. Light the paper on fire with a match. Does it catch fire? 2. Graph 1, shown in the Data and Graphs section of this lab, is a typical graph of temperature versus time obtained from the distillation of a 5 ml sample of the crude mixture. Each plateau on the graph above 30 ºC represents the temperature at which a given substance separates from the crude mixture. Use information presented in the graph to answer the following questions: a. How many fractions (different substances) are there in the crude mixture? b. What are the temperatures at which those substances should boil/distill off? c. When is it optimal to change collecting tubes during the distillation process? Part 2. Fractional Distillation of the Crude Mixture 1. Using the demonstration apparatus for reference (and/or the picture included), set-up your lab equipment for the fractional distillation of a liquid. a. Add 50 ml of the crude mixture and a few porcelain boiling-chips to a flask. b. Place the thermometer bulb close to the top of the flask containing the crude mixture so that it measures the temperature of the vapor that condenses in the outlet tube. The thermometer should be used to show when collecting tubes should be changed to receive different fractions (substances). c. Gather a clean, labeled test tube for each fraction you expect to collect. Place collection test tubes in a beaker with ice water. Then insert distillation tube into first test tube. 2. Using a hot plate, slowly heat the liquid, using just enough heat to keep it boiling. Safety! It is important that you wear safety goggles during the distillation! 3. Record the temperature of the vapor from the boiling liquid every (30) seconds during distillation. Record your data in Data Table 2. Do not forget to change collecting tubes for each fraction at the appropriate temperatures that you identified in Part 1 by moving the distillation tube to a new collection tube. Part 3. Determine Properties of the Fractions 1. Use the procedures from Part 1 (that you used to determine the properties of the crude mixture) to determine the same properties of each fraction collected. * special note: when calculating Density of the fractions, the volume value will not be 50ml - you will need to measure the volume of each fraction 2. Graph the data in Data Table 2. Use this information to determine the boiling point of each fraction. 2
Data and Results Data Tables Data Table 1. Properties of Crude Mixture and Fractions Property Unknown Crude Mixture Fraction #1 Fraction #2 Appearance Odor Mass (g) (mass of substance in grad. cylinder - mass of graduated cylinder) Volume (ml) 50 Density (g/ml) Flammability (yes/no) Boiling Point (determine from graphs) N/A Data Table 2. Temperature vs. Time of the Distillation of a 50 ml Sample of Crude Mixture Time (min) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 Time (min) 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 Time (min) 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5 3
Graphs 1. Graph 1. Temperature vs. Time of the Distillation of a 5 ml Sample of Crude Mixture 2. Graph 2. Create a graph that accurately presents the experimental data collected in Data Table 2. 4
Discussion 1. Explain the characteristic properties of matter that the process of fractional distillation relies upon. Why and how does this process work? 2. Based on their physical properties, attempt to identify the separated fractions from this simulation. Explain your response. 3. Explain why the curve in Graph 1 should resemble the curve in Graph 2. 4. What step in the Fossil Fuel Resource Cycle does fractional distillation demonstrate? Why is this step important? Application 5. Petroleum is a complex mixture of substances that can be separated into useful substances using the process of fractional distillation. Identify 3 products formed from the distillation of petroleum and explain their uses. 5