Using Stories from ChemMatters to Teach Introductory Chemistry

Transcription

1 LIVE INTERACTIVE YOUR DESKTOP Using Stories from ChemMatters to Teach Introductory Chemistry Presented by: Michael Tinnesand and Debbie Pusateri October 7,

2 Introductory Activity Gaining and Losing Lexovans Lexovans are either lost or gained in the formation of birgic substances. In dactonic (non-birgic) substances, mergs achieve filled lexovan clives by sharing lexovans rather than by losing or gaining lexovans. Many dactonic substances are composed of mergs of nonrovans that do not readily lose lexovans. As you will see, the sharing of lexovans between two nonrovan mergs allows both mergs to complete their outer clives.

3 Comprehension study questions. 1. What happens to lexovans when birgic substances are formed? 2. What is a dactonic substance? 3. Tell one way a birgic substance differs from a dactonic substance.

4 Thinking about Reading 1. Could you answer the questions? Yes X No 2. Did the questions help in extracting meaning from the passage? Yes X No 3. Would vocabulary have helped in reading the passage? How? [type your responses in the chat]

5 Now, once again. electron = lexovan ionic = birgic ion= birg molecule = dacton molecular = dactonic atom = merg atomic = mergic metal = rovan shell = clive

6 Gaining and Losing Electrons Electrons are either lost or gained in the formation of ionic substances. In molecular (non-ionic) substances, atoms achieve filled electron shells by sharing electrons rather than by losing or gaining electrons. Many molecular substances are composed of atoms of nonmetals that do not readily lose electrons. As you will see, the sharing of electrons between two nonmetallic atoms allows both atoms to complete their outer shells. From Chemistry in the Community, 4th Edition

7 Let s pause for questions from the audience

8 To Read and Understand Chemistry, Students need: Access to a variety of reading material they can and want to read. Explicit instruction across the curriculum that builds skill and desire to read increasingly complex materials. Reading material that helps students understand abstract concepts by putting it in a familiar context Source: Commission on Adolescent Literacy, International Reading Association (2000)

9 Reading comprehension and study strategies: Self-questioning Identifying, understanding, and remembering key vocabulary Recognizing and using text organization Organizing information in notes Source: Commission on Adolescent Literacy, International Reading Association (2000)

10 Reading comprehension and study strategies: Interpreting diverse symbol systems Judging one s own understanding Evaluating authors ideas and perspectives Source: Commission on Adolescent Literacy, International Reading Association (2000)

11 ChemMatters is a quarterly magazine designed to connect adolescent readers with the chemistry that matters in their everyday lives.

12 Examples of popular ChemMatters articles Plastics Go Green, Concept of polymer/plastic introduced in the beginning, followed with description of bioplastics and their applications. What s in Sunscreens? UV light defined in context of electromagnetic spectrum and light wave, followed with discussion of UV-A vs. UV-B, chemicals in sunscreens and sun protection factor (SPF). The Chemistry of Marathon Running, Describes the chemical changes that go on inside a runners body during a long distance race.

13 Integrate into Daily Instruction After you have introduced a new concept, use an article from ChemMatters to illustrate how it relates to everyday life. Or, consider introducing a concept with an article from ChemMatters and continue with regular instruction. As independent reading material for student research projects or curriculum enhancement (such as Talented and Gifted students).

14 Let s pause for questions from the audience

15 A Sample Lesson Green Gasoline: Fuel from Plants February, 2010 Given the limited future of fossil fuel oil resources, this article explores alternative gasoline sources from plant material.

16 Connections to Chemistry Concepts Where does the story on Green Gasoline fit into the typical introductory chemistry course? Types of chemical reactions, combustion This whole article features combustion, although the focus is on sustainable fuels. Chemical bonding Bond-breaking is endothermic; bond-forming is exothermic. Sustainability Although sustainability is not a concept presently contained in first-year chemistry courses, perhaps it should be. The need to provide a continuous supply of fuels and materials for humanity is a central concern for chemical industry everywhere. Producing green fuels is a step in the right direction for all of us.

17 Anticipation Guide: Green Gasoline Before reading place your choice of clip art under Agree or Disagree to indicate your agreement or disagreement with each statement. Agree Disagree Statement Green gasoline is a nonrenewable source of energy. When hydrocarbons burn, carbon dioxide and water are produced and a large amount of energy is released. Green gasoline would directly replace gasoline derived from crude oil.

18 NSES Correlation For Green Gasoline National Science Education Standards addressed Science as Inquiry Standard A About scientific inquiry Physical Science Standard B Of the structure and properties of matter. Chemical properties Science & technology Standard E About science and technology Science in Personal & Social Perspective Standard F About natural resources About environmental quality Of science and technology in local, national and global challenges History & Nature of Science Standard G Of science as a human endeavor of the nature of scientific knowledge

19 Green Gasoline Reading Guide Advantages Who is working to develop it? What have they tried? What problems must still be solved?

20 Green Gasoline: Student Questions 1. What are three advantages to using green gasoline? 2. Why is green gasoline preferred over other biofuels, such as ethanol 3. Why has gasoline been the transportation fuel of choice for the past century? 4. What is a hydrocarbon? 5. What gases are heated in the internal combustion engine? 6. Why does green gasoline help reduce the problem of global climate change? 7. Why can t wood be used to fuel cars? 8. Why are carbohydrates poorer fuels than their corresponding hydrocarbons? 9. What is meant by the term, plant leftovers? What are some examples? 10.What is the role of a zeolite catalyst? 11.What logistical problems face the production and use of green gasoline?

21 Sample Background for Green Gasoline Gasoline is a complex mixture composed primarily of hydrocarbons. It is part of crude oil. Gasoline contains more than 500 hydrocarbons having between 3 and 12 carbon atoms, in both saturated and unsaturated molecules. In the early history of petroleum, gasoline was not particularly useful because most of petroleum was refined to produce kerosene for kerosene lamps. Cracking is the process by which longer-chain hydrocarbons are broken down (cracked) into smaller chains, including heptane and octane, that go into making gasoline. Two methods of cracking were developed.

22 Green Gasoline Misconceptions We ll never run out of oil why are we so worried about running out? There are millions of barrels of oil still buried underground. While this is a true statement, we consume millions of barrels of oil daily. Eventually, we will run out of oil that is presently stored underground. We must find (grow) replacements for this fuel source. Breaking bonds releases energy it says as much in the article: Octane and other hydrocarbons burn by breaking bonds between carbon and hydrogen atoms The remaining part of that quote, which then grab onto oxygen atoms finishes the thought, implying that the carbon and hydrogen atoms grabbing onto (bonding with) oxygen atoms is the part that really releases the energy. Gasoline must be the only thing produced from crude oil. Crude oil is used in many other types of fuels besides gasoline diesel, kerosene and jet fuel, just to name a few, in addition to petrochemicals used for products.

23 Let s pause for questions from the audience

24 An exercise from the ACS General Chemistry textbook project, published by W.H. Freeman and Co. 7.7 Bond Enthalpies Chemical Reactions: Making and Breaking Bonds Given the average bond enthalpies for the bonds, you can calculate an approximate value for the enthalpy change in this reaction by breaking, hypothetically, all the bonds in the reactants to form separate atoms, then forming the desired bonds to for the products. ACS/W.H. Freeman GenChem Project

25 Green Gasoline Combusion Ethane vs. Ethanol C 2 H 5 OH + 3 O 2 2 CO H 2 O vs. C 2 H 6 + 7/2 O 2 2 CO H 2 O

26 C 2 H 5 OH + 3 O 2 2 CO H 2 O First, calculate the energy required to break all the bonds in a mole of ethanol and 3 moles of oxygen. H H O=O H C C O H + O=O O=O H H 5 moles of C H bonds? 1 mole of C C bonds? 1 mole of C O bonds? 1 mole of O H bonds? 3 moles of O=O bonds? Here are average bond energies (in kj/mol) needed to solve the following problem: C H 413 kj/mol C C 347 kj/mol C O 358 kj/mol C=O 799 kj/mol O H 467 kj/mol O=O 495 kj/mol

27 C 2 H 5 OH + 3 O 2 2 CO H 2 O The energy required to break all the bonds in a mole of ethanol and 3 moles of oxygen is: H H O=O H C C O H + O=O O=O H H 5 moles of C H bonds 5 x 413 kj = 2065 kj 1 mole of C C bonds 1 x 347 kj = 347 kj 1 mole of C O bonds 1 x 358 kj = 358 kj 1 mole of O H bonds 1 x 467 kj = 467 kj 3 moles of O=O bonds 3 x 495 kj = 1485 kj 4722 kj total Here are average bond energies (in kj/mol) needed to solve the following problem: C H 413 kj/mol C C 347 kj/mol C O 358 kj/mol C=O 799 kj/mol O H 467 kj/mol O=O 495 kj/mol

28 C 2 H 6 + 7/2 O 2 2 CO H 2 O Now calculate the amount of energy to break apart one mole of ethane molecules and 3.5 moles of oxygen molecules H H O=O H C C H + O=O O=O H H 1/2 O=O requires the following energies: 6 moles of C H bonds? 1 mole of C C bonds? 3.5 moles of O=O bonds? Here are average bond energies (in kj/mol) needed to solve the following problem: C H 413 kj/mol C C 347 kj/mol C O 358 kj/mol C=O 799 kj/mol O H 467 kj/mol O=O 495 kj/mol

29 C 2 H 6 + 7/2 O 2 2 CO H 2 O Breaking apart one mole of ethane molecules and 3.5 moles of oxygen molecules requires the following energy: H H O=O H C C H + O=O O=O H H 1/2 O=O 6 moles of C H bonds 6 x 413 kj = 2478 kj 1 mole of C C bonds 1 x 347 kj = 347 kj 3.5 moles of O=O bonds 3.5 x 495 kj = kj kj total Here are average bond energies (in kj/mol) needed to solve the following problem: C H 413 kj/mol C C 347 kj/mol C O 358 kj/mol C=O 799 kj/mol O H 467 kj/mol O=O 495 kj/mol

30 Summary Amount of energy to break ethanol (and required amt of oxygen)=4722 kj Amount of energy to break ethane (and required amt of oxygen)= kj kj = kj Thus it requires kj more energy to break apart a mole of ethanol than a mole of ethane.

31 Now we need to calculate the amount of energy released when the products form. C 2 H 6 + 7/2 O 2 2 CO H 2 O C 2 H 5 OH + 3 O 2 2 CO H 2 O Note the products are identical in each reaction. O O O O=C=O + O=C=O + / \ + / \ + / \ H H H H H H Calculate the amount of energy released when the products form. 4 moles of C=O bonds? 6 moles of O H bonds? Here are average bond energies (in kj/mol) needed to solve the following problem: C=O 799 kj/mol O H 467 kj/mol

32 The amount of energy released when the products form is given below: C 2 H 6 + 7/2 O 2 2 CO H 2 O C 2 H 5 OH + 3 O 2 2 CO H 2 O Note the products are identical in each reaction. O O O O=C=O + O=C=O + / \ + / \ + / \ H H H H H H 4 moles of C=O bonds 4 x 799 = 3196 kj 6 moles of O H bonds 6 x 467 = 2802 kj 5998 Here are average bond energies (in kj/mol) needed to solve the following problem: C=O 799 kj/mol O H 467 kj/mol

33 Since ΔH = H bonds broken H bonds formed, we can calculate ΔH for both reactions: For ethanol, ΔH combustion = = kj/mol C 2 H 5 OH For ethane, ΔH combustion = = kj/mol C 2 H 6 Here are the bond energies (in kj/mol) needed to solve the following problem: Ethanol H bonds broken = 4722 kj/mol Ethanol H bonds formed = 5998 kj/mol Ethane H bonds broken = kj/mol Ethane H bonds formed = 5998 kj/mol

34 Since ΔH = H bonds broken H bonds formed, we can calculate ΔH for both reactions: For ethanol, ΔH combustion = 4722 kj/mol 5998 kj/mol = 1276 kj/mol C 2 H 5 OH For ethane, ΔH combustion = kj/mol 5998 kj/mol = kj/mol C 2 H 6 The calculations show that the combustion of one mole of ethane produces kj more energy than the combustion of one mole of ethanol.

35 Let s pause for questions from the audience

36 Demonstrations and Lessons Do a simple calorimetry lab using various energy sources, such as propane, butane, ethanol, methanol or kerosene. Use molecular models to build the organic molecules discussed in the article. Have students visit (or show them) one of the excellent animations on the web of how automobile engines work

37 Green Gasoline Student Projects Students can research and report on other biofuel sources, such as soybeans, switchgrass and algae. Students can compare and contrast existing biofuels in areas such as: fuel efficiency, cost per kj of energy, land mass needed to grow energy-equivalents of each, energy needed to grow/prepare biofuels, net energy output, etc. Have students do their own back of the envelop calculation on the amount of land required to grow plants for green gasoline production similar to fossil fuel gasoline supplies.

38 Anticipating Student Questions 1. Why is green gasoline the only fuel that can be used directly in cars and pipelines without further modifications why can t ethanol be used directly in cars and pipelines? 2. Where does our (US) oil come from? 3. Can cars run on fuels other than gasoline?

39 References and Websites for Additional Information Each article has references Print references include related ChemMatters articles as well as other books and journals. Numerous websites on topics related to the main article

40 Where is your current curriculum? To what extent is reading instruction part of your chemistry curriculum? Not at all Big Emphasis Place clip art in the rectangle above, to show where your curriculum is now.

41 Additional Questions What topics need additional reading materials that could be featured in ChemMatters? (respond in chat.) Are the resources in this web seminar helpful? Yes X No

42 Thank you to the sponsor of tonight's Web Seminar: 42

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45 National Science Teachers Association Dr. Francis Q. Eberle, Executive Director Zipporah Miller, Associate Executive Director Conferences and Programs Al Byers, Assistant Executive Director e-learning NSTA Web Seminars Paul Tingler, Director Jeff Layman, Technical Coordinator LIVE INTERACTIVE YOUR DESKTOP 45