Chemistry Of Petroleum three: Distillation Of Hydrocarbons
To introduce how hydrocarbons in crude oil are distilled and handled in the refinery process to produce useful materials.
This lesson is the third in a sequence of classes in regards to the chemistry of petroleum which might be meant for higher-degree chemistry college students in the 11th and twelfth grades. You ought to be an skilled chemistry trainer to show these lessons. The purpose of those classes is to introduce high-college students to the usage of oil as an power supply in today’s high-tech world. In the Chemistry of Petroleum 1: What are Hydrocarbons students will discover hydrocarbons, the molecular basis of petroleum, and be taught to tell apart between natural and inorganic compounds.
In this lesson, the Chemistry of Petroleum three: Distillation of Hydrocarbons, students will probably be introduced to the distillation and therapy processes by which petroleum is refined to provide helpful gasoline oils.
This particular lesson provides the chance to handle numerous misconceptions that students have about the physical world. Sometimes, terminology can inadvertently cause students to develop such misconceptions. The time period “fossil fuel” can sometimes be misleading as it implies that crude oil is product of or derived from fossils. Through the motivation part of this lesson, it may be useful to make clear the difference between a true fossil and fossil fuels. Fossils are the preserved remains or traces of life forms from the past, typically by way of the means of permineralization. Fossil fuels are produced from decayed natural matter that has modified chemically over geologic time as a consequence of high ranges of heat and stress. The term “fossil fuel” is used for substances such as coal, natural gas, and crude oil or petroleum, because the natural life types lived millions of years ago.
Another false impression among students is that crude oil is composed of particular person molecules of diesel, kerosene, and the other refined products. This misconception might emerge if college students think of the refinery course of as a sieve by which these products are sorted out from crude oil. The analogy of a sieve is an effective one if students understand that the refined merchandise are usually not particular person molecules, but a set of chemically similar molecules. In different words, there isn’t any single molecule often called diesel, or kerosene, or light gases, with a selected chemical formulation. In distinction, water is a molecule outlined by a selected chemical system of H2O. Diesel, however, is a mixture of various molecules that share the identical properties. The chemical property that is essentially utilized to kind the various hydrocarbons in crude oil is boiling level. The sieve within the refining course of separates hydrocarbon molecules of comparable size—and subsequently, similar chemical properties. Particular collections of equally sized hydrocarbon molecules are referred to as diesel, kerosene, mild gases, and the other various refined products.
When watching Oil Refining: A more in-depth Look, it is helpful to also address that the composition and appearance of crude oil will fluctuate depending upon its source. The interactive exhibits a thick, black, liquid substance; however, crude oil might be brown, yellow, and even green relying upon its chemical composition. It also will be found in a semi-solid kind that does not circulation simply until after it’s heated or diluted.
Research shows that students have many misconceptions about heat, temperature, and part changes reminiscent of boiling. (Benchmarks for Science Literacy, p. 337.) A easy misunderstanding that college students might have is that a substance can change phases (i.e. from liquid to gasoline), while nonetheless remaining intact in its chemical composition. In the steam furnace animation within the distillation process, point out to students that the molecular construction of hydrocarbons doesn’t change when they modify section from liquid to gas. It’s also necessary to point out that this phase change shouldn’t be a function of temperature alone. The boiling point of a liquid is determined not only by heat, but in addition by the atmospheric stress across the liquid. In the event part of the lesson, a chance is provided to debate why water boils at a lower temperature at high altitudes. This may assist to clarify the misunderstanding that boiling point is a operate of a temperature studying.
Start by reviewing what crude oil is, how it’s formed, and its relevance to human lives by having students use their Oil Refining scholar esheet to watch the introductory animation from Oil Refining: A more in-depth Look. The film has an accompanying script that you can print out. The narrator speaks quickly, so it is a good idea to read the script after watching the movie the primary time. After studying the script, students can watch the film a second time, which will facilitate understanding.
Provide the Understanding Crude Oil scholar sheet to students as they watch the animation. They should answer the questions on this sheet.
Question 9 supplies a chance to elucidate how petroleum rises to the floor over time. To assist solidify this idea with college students, have them do a quick activity with vegetable oil and water (you possibly can do this as a demonstration if you desire). They need to first pour the vegetable oil into a transparent glass, beaker, or cylinder. Ask students:
– What occurs when oil and water are mixed
Now ask college students to pour the water on high of the oil. The two phases will separate shortly. Ask students:
– Which section is now on high
Explain to students that vegetable oil is a mixture of hydrocarbons from plants, just like kerogen. Be sure that college students perceive that vegetable oil isn’t a fossil gasoline like kerogen as a result of it’s not produced from organic matter hundreds of thousands of years previous that skilled high pressures and temperatures over time. Inform college students that if the highest of the glass represented the bottom, the oil can be sitting on the floor of the earth and would finally evaporate or be broken down by micro organism. Place your hand excessive of the glass and tell students that it represents non-porous rock, corresponding to shale. Explain that in petroleum exploration, a rock that holds back the petroleum from coming out in the direction of the floor is called a cap rock or seal rock. As a result of the cap rock is non-porous, the petroleum fills up beneath it like a reservoir. The rocks immediately under the cap rock are porous, because the petroleum was in a position to maneuver by way of these rocks. In petroleum exploration, scientists look for these cap rocks above porous rocks to seek for deposits. If obtainable, move around a sample of shale rock, stating that it has no pores or openings. A glazed tile also can represent a non-porous cap rock. Enable college students to pour vegetable oil onto the rock or tile to see that it will merely roll off and never be absorbed, just as with a cap rock.
Have college students proceed to the subsequent a part of the interactive, “Let’s Distill.” It natural gas kit for generator is suggested to undergo the five hotspots collectively as a category. This may be sure that college students all perceive the essential concepts around distillation and remedy of petroleum.
Level out the yellow barrel labeled “crude oil”. Inform students that once the petroleum has been extracted from the bottom, it is distributed to refineries. The interactive simulates and describes the assorted chemical processes that petroleum undergoes as a way to make helpful products.
– What’s crude oil composed of
Click on on the “Dump Crude Oil” button after which roll over the hotspot and read the description. Discuss with college students that crude oil is made up of various compounds. Make sure that students do not suppose that the assorted compounds are floating around inside crude oil, however that crude oil itself is the collection of those compounds. Tell college students that crude oil will fluctuate in its composition relying on its geographic location. Usually, it is composed of a mix of straight-chained hydrocarbons and ringed hydrocarbons. Level out that there are some sulfur and nitrogen compounds blended with the hydrocarbons as properly. Remind college students that kerogen additionally contained sulfur and nitrogen.
Click on on the “Dump Crude Oil” button once more. Ask students:
– The place does the crude oil go
Earlier than proceeding, present each student with a table of hydrocarbon boiling factors from Boiling Points and Buildings of Hydrocarbons. Ask students:
– Once you look on the “name” and “molecular formula” columns, what sample do you notice as you go down
Evaluate the concept of boiling level with students by having them do a quick fingers-on exercise of boiling water with a thermometer positioned within the water. Have students convey some water to a boil. Once it reaches the boiling point, ask them:
– What is going on to a substance when it begins to boil
College students ought to place the thermometer into the boiling water and browse the temperature. A standard misconception amongst students is that the temperature of a boiling substance will increase as it boils. To assist right this misconception, allow college students to see that the temperature of the boiling water stays at 100 degrees Celsius because it boils. One other common misconception is that the boiling level is when a liquid turns into gas, and not vice versa. It is vital to deal with that boiling point is a phase change between liquid and gas. It’s the purpose when a liquid turns into gasoline and a gasoline turns into liquid. Level this out to college students by showing that the boiling water can be viewed as liquid turning into gas, or gasoline turning into liquid.
Tell college students that on Mount Everest, water boils at 69 levels Celsius. Ask students:
– What makes the summit of Mount Everest completely different from sea stage
Review with college students that the boiling level of a substance will not be a operate of temperature alone. What determines when a substance will change from liquid to gas is each temperature and the surrounding atmospheric pressure. College students are sometimes conscious, by means of their lived expertise, that a change in temperature will alter a substance’s section. For instance, water positioned in the freezer adjustments into ice, and water that is heated to one hundred levels Celsius boils and becomes a gasoline. Nonetheless, they often do no make the connection that pressure is equally as essential in figuring out the part of a substance. To help make this level extra clear, ask college students to imagine a balloon that incorporates air molecules. Tell college students that temperature is a measure of heat. If the balloon is heated, the kinetic power of the molecules contained in the balloon additionally increases and they begin to interrupt away from one another and move faster. Ask college students:
– What is going to occur to the size of the balloon as the heat and corresponding kinetic energy of the molecules increase
The barrier of the balloon represents the exterior air strain. It holds the air molecules again from increasing out any additional. At some point, because the heat will increase, the balloon will burst. That bursting represents boiling as a result of at that time, the strain contained in the balloon becomes equal to the stress outside of the balloon. Equally, a liquid boils when its internal strain is equal to the atmospheric stress.
Going again to the example of Mount Everest, tell students that water boils at a lower temperature on the mountain (69 levels Celsius) as a result of at that time, its pressure is equal to the low atmospheric stress on Mount Everest. As you descend from Mount Everest and come to sea stage, the atmospheric strain is extra, so correspondingly more heat is required to cause boiling (100 degrees Celsius).
Return back to the desk of hydrocarbon boiling factors from Boiling Factors and Constructions of Hydrocarbons. Ask students:
– Why do you assume that the boiling point of alkanes is related to the dimensions of the molecules
Point out that pentane by way of dodecane are liquid at room temperature. Ask college students:
– Of the eight alkanes, which one has the highest boiling level
Evaluate dodecane to an extended spaghetti strand. On account of its longer size in comparison with that of a smaller pentane molecule, dodecane molecules will wrap round each other, making it more durable to separate them as a result of of those strong forces.
– If all these alkanes have been blended collectively in a pot, and the temperature was elevated to 250 levels Celsius, what would occur to all these alkanes
Return back to the interactive. Remind college students that crude oil or petroleum is a mixture of hydrocarbons. The oil is now within the furnace and will likely be heated. Click on “Begin Furnace” and roll over the hotspot and have students focus on a single hydrocarbon molecule. Ask college students:
– If all the hydrocarbons are superheated, what phase will they go into
Point out that the furnace has now superheated the crude oil parts which are now in vapor form. Indicate that the vapor has now traveled to the distillation column where the vapor rises. Point out the temperature gradations on the facet of the distillation column.
Roll over the hotspot on the left side of the distillation column and point out that the animation shows two completely different hydrocarbon molecules—methane and cyclopentane. Ask students:
– Which one could have a decrease boiling level
Roll over the hotspot at the highest right corner of the distillation clumn. Present college students that all of the smaller chained hydrocarbons gather higher up within the distillation column. The collections of these comparable hydrocarbons are called fractions. Examples of lighter fractions are gasoline and naphtha. Rolling over the hotspot at the lower proper nook of the distillation column will present students heavier fractions, comparable to diesel.
Naphtha is a group of hydrocarbons in the C5, C6, and C7 vary. These hydrocarbons are all very mild, easily vaporized, and type a transparent liquid. Eventually, after remedy, naphthas are used as solvents in dry cleansing, paint, and different industries that need fast-drying products. Gasoline is a group of hydrocarbons in the C7 and C11 vary. Diesel is composed of hydrocarbons in the C16 range. As a result of they are bigger hydrocarbons, their boiling level is way greater and will condense into liquid decrease in the distillation column where the temperature is larger. Be sure that students understand that the collected fractions usually are not one molecule, however moderately a collection of hydrocarbons of related size, and thus, similar boiling point temperatures.
Tell college students that distillation is the first a part of the petroleum refining course of. The fractions must now bear treatment for 2 reasons. First, the hydrocarbon fractions still have substances in them reminiscent of sulfur, which have to be eliminated. Second, a few of the longer hydrocarbon fractions should be chemically altered and shortened into smaller chains to be able to develop into more helpful merchandise.
To assess students’ understandings of the primary concepts coated in this lesson, ask them to finish the Assessing Our Understanding of Crude Oil student sheet. Tell college students that the ten questions tackle misconceptions that most people has about crude oil. Have college students full the sheet individually. As soon as all the students have chosen their answers, ask students to work in small teams and share their responses to every question with their group members. Every group must determine on their collective reply to every query. Provide classroom time for student teams to share with each other. Encourage students to debate misconceptions and why these misconceptions might exist in the general public. For teachers, this is also an excellent opportunity to evaluate if college students are understanding the main concepts via the lessons. The Assessing Our Understanding of Crude Oil instructor sheet offers solutions to the questions.
Explore the usage of vegetable oil, used in the motivation part of this lesson, as a fuel itself. The Bio-Fuel Challenge, from the Power Efficiency and Renewable Energy site, offers an in depth, two-week curriculum wherein students learn to make their own biodiesel fuel from waste vegetable oil.
To additional emphasize the connection between the boiling point of a substance and atmospheric stress, use NASA’s lesson, Testing Your Speculation by Boiling Water Below Its Boiling Temperature.
Acid Rain: Effects Felt By means of the Meals Chain, from Nationwide Geographic, offers information about the fundamental causes and effects of acid rain, including images and what humans can do to lower its prevalence.
Local weather Change: Basic Information, from the U.S. Environmental Safety Company, supplies comprehensive information on the issue of worldwide warming and local weather change.
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