Understanding The Mole Chemistry HS/Science Unit: 06 Lesson: 01 Suggested Duration: 8 days Lesson Synopsis: Students will investigate the mole concept, and use it to explore the idea of gram atomic mass for elements, gram formula mass for ionic compounds, and gram molecular mass for molecular compounds. The relationship between area, mass, and moles will be used to solve an authentic problem, the cost of an atom of aluminum. TEKS: C.8 The student can quantify the changes that occur during chemical reactions. The student is expected to: C.8A C.8B Define and use the concept of a mole. Supporting Standard Use the mole concept to calculate the number of atoms, ions, or molecules in a sample of material. Readiness Standard Scientific Process TEKS: C.2 The student uses scientific methods to solve investigative questions. The student is expected to: C.2E C.2F C.2G C.2I Plan and implement investigative procedures, including asking questions, formulating testable hypotheses, and selecting equipment and technology, including graphing calculators, computers and probes, sufficient scientific glassware such as beakers, Erlenmeyer flasks, pipettes, graduated cylinders, volumetric flasks, safety goggles, and burettes, electronic balances, and an adequate supply of consumable chemicals. Collect data and make measurements with accuracy and precision. Express and manipulate chemical quantities using scientific conventions and mathematical procedures, including dimensional analysis, scientific notation, and significant figures. Communicate valid conclusions supported by the data through methods such as lab reports, labeled drawings, graphs, journals, summaries, oral reports, and technology-based reports. C.3 Scientific processes. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions within and outside the classroom. The student is expected to: C.3F Research and describe the history of chemistry and contributions of scientists. GETTING READY FOR INSTRUCTION Performance Indicator: Given the cost and area of a roll of aluminum foil, plan and implement an investigation to determine the cost of a single atom of Al. Record all assumptions, procedures, data, and calculations in your science notebook. Summarize how Avogadro s number and molar mass were used. (C.2E, C.2F, C.2G, C.2I; C.8A, C.8B) 1C; 3F; 5G Key Understandings and Guiding Questions: The mole is a fundamental SI unit in science. How is the mole defined in terms of mass and particles? A mole of anything contains Avogadro s number of particles (molecules, atoms, formula units, etc.) How is the mass of one mole of an element calculated? How is the mass of one mole of a compound calculated? How is molar mass used to calculate the number of moles in any given mass of an element, compound, or ionic substance? How is Avogadro s number used to calculate the number of representative particles in one mole of an element or a compound? How is Avogadro s number used to calculate the number of representative particles in any given mass of an element or compound? How are density, volume, and mass related to moles and representative particles? Vocabulary of Instruction: mole concept Avogadro s number representative particles molecule formula unit molar mass molecular formula gram formula mass gram atomic mass 2012, TESCCC 05/07/13 page 1 of 10
gram molecular mass density Chemistry HS/Science Unit: 06 Lesson: 01 2007 CSCOPE MM/DD/YY page 2 of 11
Refer to section for materials. Handout: Moles of Moles (1 per group) Teacher Resource: Moles of Moles KEY Handout: Dozens, Dozens, Dozens (1 per group) Teacher Resource: Dozens, Dozens, Dozens KEY Teacher Resource: Mole Labels (see Advance Preparation, 1 per set) Handout: Matters of Matter Solids (1 per pair) Teacher Resource: Matters of Matter - Solids KEY Handout: Matters of Matter Pure Liquids (1 per student) Teacher Resource: Matters of Matter - Pure Liquids KEY Handout: Mole Potpourri (1 per group) Teacher Resource: Mole Potpourri KEY Handout: Foiled Again PI (1 per student) Teacher Resource: Foiled Again PI KEY Teacher Resource: Performance Indicator Instructions KEY Advance Preparation: 1. Prior to Day 1, gather a pair of socks, an empty egg carton, a bundle of twenty pencils, a gross of straws (144), and a ream of paper. Create a sign that says 21 st Century. 2. Prior to Day 3 Molar Mass Activity: Prepare two sets of containers of one mole of: sodium chloride (58.5 g), water (18 ml), sucrose (342 g), copper wire (63.5 g), aluminum foil (27 g), and room temperature oxygen (really air)(24.5 L). Label each container 1 mol. Small jars you can reuse would be good for the solids and water. NOTE: For oxygen at room temperature (25 o C) and standard pressure (760 mm Hg), the molar volume is 24.5 L. At STP - standard temperature (0 o C) and pressure.(760 mm Hg) - the molar volume is 22.4 L. Following are two alternatives for modeling a mole of oxygen at room temperature: 1) Tape together 24 1-L soda bottles, 12 2-L soda bottles, or 8 3-L soda bottles. 2) Construct a room temperature (25 o C) Mole Box, a cube with edges of 29 cm. Use the Teacher Resource: Mole Labels for the containers. NOTE: Alternatively, you could make an STP Mole Box. If you choose this option, the cube should be 28.2 cm on a side. This could then be used again in Unit 09, Gases. Additionally, the American Chemical Society sells a 22.4 L beach ball. 3. Prior to Day 5: Prepare three containers of water to represent the molar volumes of water, isopropyl alcohol, and hydrogen peroxide for display in Matters of Matter - Pure Liquids. Label each with the name, chemical formula, and 1 mol. 1 mole of water (H 2O) is 18.0 ml (Density = 1.00 g/ml) 1 mole of hydrogen peroxide (H 2O 2) is 23.0 ml (Density = 1.46 g/ml) 1 mole of isopropyl alcohol (C 3H 7OH) is 77.0 ml (Density = 0.785 g/ml) 4. Prior to Day 6, obtain some empty, non-hazardous household materials containers to use as examples in the Elaborate Mole Day Celebration. 5. Prior to Day 7, review the Teacher Resource: Performance Indicator Instructions KEY. Cut pieces of aluminum foil in 20 x 20 cm squares. You will need one per student. 6. Prepare attachment(s) as necessary. Background Information: This unit bundles student expectations that apply the concepts of the previous two units to the mole concept. Prior to this lesson, students have not been directly introduced to the concept of the mole. During this lesson, students will develop an understanding of Avogadro s number and how to apply it to atoms, formula units, and molecules. The concept 2012, TESCCC 05/07/13 page 3 of 10
of the molar mass of substances will be introduced. Avogadro s number and the molar mass of a substance will be used in chemical calculations. After this unit, students will use the mole concept as they are introduced to equations, reactions, and stoichiometry in upcoming units. The mole is one of the seven SI base units and a measure for the amount of a substance. Its symbol is mol. By definition, the mole is the amount of substance in a system that contains as many elementary entities (atoms, molecules, ions, electrons, other particles) as there are atoms (6.02x10 23 ) in 0.012 kilogram of carbon-12. Avogadro s number is named after Amedeo Avogadro, a nineteenth-century Italian scientist. In 1811, Avogadro proposed that the volume of a gas at a given pressure and temperature is proportional to the number of particles (atoms or molecules) it contains, regardless of the type of gas. In 1909, French physicist Jean Perrin proposed naming the number in honor of Avogadro. Perrin won the 1926 Nobel Prize in Physics, in large part for his work in determining Avogadro s number by a variety of methods. STAAR Notes: Using the mole concept to calculate the number of atoms, ions, or molecules in a sample of material will be tested as a Readiness Standard under Reporting Category 3: Bonding and Chemical Reactions. The STAAR Chemistry Reference Materials includes Avogadro s number (listed under Constants and Conversions). GETTING READY FOR INSTRUCTION SUPPLEMENTAL PLANNING DOCUMENT Instructors are encouraged to supplement and substitute resources, materials, and activities to differentiate instruction to address the needs of learners. The Exemplar Lessons are one approach to teaching and reaching the Performance Indicators and Specificity in the Instructional Focus Document for this unit. Instructors are encouraged to create original lessons using the Content Creator in the Tools Tab located at the top of the page. All originally authored lessons can be saved in the My CSCOPE Tab within the My Content area. INSTRUCTIONAL PROCEDURES Instructional Procedures ENGAGE 1 1. Display a 2-lb bag of popcorn and piece of metal. Ask: What are some similarities and some differences between this bag of popcorn and this piece of metal? 2. Instruct students to write their answers silently in their notebooks. Monitor the process. If anyone has difficulty, hint at what can be seen and not seen. 3. Ask students to share their observations with their table group or a partner. 4. Ask groups to share their observations with the class. If not brought up by the students, ask the following questions: Can you count the number of kernels of popcorn? How? How about the number of atoms in the metal? How could we do that? Accept all reasonable answers; use student answers to transition to the Explore/Explain activity. NOTE: 1 Day = 50 minutes Suggested Day 1 piece of elemental metal (such as iron or lead, 1 per teacher) bag of popcorn (un-popped, 2-lb, 1 per teacher) Instructional Notes: Consider making a display of Mole Humor in your classroom by finding websites that offer jokes and riddles involving the mole. For riddles, display only the prompts, but not the answers to the jokes. Instruct students to come see you for a prize (of your choice) if they think they know the answer. First come, first prize. Have a special reward available if students come up with an original riddle to add to the Mole Humor wall. 2012, TESCCC 05/07/13 page 4 of 10
EXPLORE/EXPLAIN I What is a Mole? 1. Display a pair of socks, an empty egg carton, a bundle of 20 pencils, a sign that says 21 st Century, a box of 144 straws, and a ream of paper (see Advance Preparation). While holding each object, or set of objects, for students to view, ask the following questions. Accept reasonable answers for each question. How many socks in a pair? How many eggs in a dozen? How many pencils in a score? How many years in a century? How many straws in a gross? How many sheets of paper in a ream? Now for the BIG question, how many particles (atoms, ions, molecules) in a mole? 2. Facilitate a discussion of how the terms pair, dozen, score, century, gross, and ream make it easier to measure or describe a specific quantity. 3. Explain to students that we have a special word in chemistry comparable to these words called the mole. The quantity of the mole is Avogadro s number, 6.02x10 23. Write both on the board. 4. Ask students to record the terms and definitions for mole and Avogadro s number in their notebooks. 5. Pose the following questions: Is it reasonable to measure out a dozen, gross, or ream of atoms? Why not? 6. Discuss the size of an atom and the need to have a specific value or unit quantity of atoms. Explain that this unit quantity is the mole, and it is composed of Avogadro s number of particles. 7. Display Avogadro s number in expanded notation, 602 followed by 21 zeros. 8. Explain it is much easier to manage this value when it is expressed in scientific notation, 6.02 x 10 23. 9. Ask: Why 10 23? Accept reasonable answers. 10. Provide a pointer to a student that understands from where the 23 is derived, and ask them to count the place values while pointing at the values on the expanded notation display. 11. Make the following analogy: Even though we purchase grapes by the bunch, we eat them individually. Just like grapes, particles are grouped by the mole, even though particles interact individually. Students respond to prompts in their science notebooks. Suggested Day 1 (continued) socks (1 pair per teacher) egg carton (empty, 1 per teacher) pencils (bundled, 20 per teacher) 21 st Century sign (see Advance Preparation, 1 per teacher) straws (box of 144 per teacher) paper (1 ream, 500 sheets per teacher) scientific calculator (1 per student) glue or tape (per group) Handout: Moles of Moles (1 per group) Teacher Resource: Moles of Moles KEY Instructional Note: Watch for underdeveloped concepts. Depending on the level of your students, they may need a review of atoms, molecules, and formula units as the smallest particles of elements, compounds, and ionic substances, respectively. Expanded notation vs. scientific notation, and how to use a scientific calculator in both formats, may also need to be reviewed. You may wish to locate and share an online video demonstration of Avogadro s hypothesis. See Advance Preparation for directions to create a gas Mole Box for use each year in teaching the mole concept. STAAR Note: The STAAR Chemistry Reference Materials includes Avogadro s number under Constants and Conversions. 2012, TESCCC 05/07/13 page 5 of 10
12. Divide the class into pairs. Distribute a copy of the Handout: Moles of Moles to each group. 13. Instruct students to work through the activity, creating tables and working problems in their science notebooks. Instruct students to check each other to verify calculations and help problem solve. 14. Monitor and assist students as needed. 15. Review practice problems in the Handout: Moles of Moles with the class. Affix handouts in the notebooks. Students record terms and definitions in their notebooks. Additionally, students work problems and affix handouts in their notebooks. EXPLORE/EXPLAIN II Dozens, Dozens, Dozens Suggested Day 2 1. Inform students that today they will determine the mass of a one-dozen unit of three different items. 2. Divide the class into pairs. Distribute to each group a copy of the Handout: Dozens, Dozens, Dozens. 3. Ask students to read the activity and answer any questions they may have regarding the instructions. 4. Monitor groups as they complete the activity. 5. Instruct groups to post their data in a pre-determined location. 6. Facilitate a discussion in which students find the class average mass for each type of item. 7. Students should see that mass is different for different fasteners (brads, paper clips, screws). Relate this example to the concept of molar mass. 8. Have groups complete and discuss their analyses based on the class data. Review and answer any questions. Point out that each one-dozen unit of the fasteners in the activity has a mass and that and the average mass of each can be found as well. electronic balance (1 per group) brad fasteners (small, 12 per group) screws (small, 12 per group) paper clips (small, 12 per group) scientific calculator (1 per student) Check for Understanding: Depending on the level of your students, they could be required to use dimensional analysis in solving all problems. Handout: Dozens, Dozens, Dozens (1 per group) Teacher Resource: Dozens, Dozens, Dozens KEY Instructional Note: Students should begin to understand that Avogadro s number is the same for one mole of any substance elements, molecular compounds, and ionic compounds. Students record data and answer questions in their notebooks. EXPLORE/EXPLAIN III Molar Mass Suggested Day 3 1. Display one-mole containers of the following substances around the lab or classroom: sodium chloride, water, sucrose, copper, aluminum, oxygen 2012, TESCCC 05/07/13 page 6 of 10
(see Advance Preparation). Use the Teacher Resource: Mole Labels to create labels for the containers. Display a list of the substances on the board. 2. Say: We have explored the concept of Avogadro s number as the number of representative particles in one mole. We have observed that one mole of different substances look different, just as one-dozen of different fasteners look different. Now we will begin to explore the unique mass of substances and compare the mass of one mole of different substances. 3. Divide the class into pairs, and instruct students to create data tables in their science notebooks for the six substances you have listed: water, sodium chloride, aluminum, copper, sucrose, and oxygen. 4. Instruct groups to rotate among the containers, copying the information from the labels in their notebooks until they have information for all six. 5. Assign a substance to each pair. Note: You may wish to print the list and cut out individual strips of paper for each substance. Then, place the strips in a paper bag and have students draw the substance they are then assigned. 6. Instruct students to use a periodic table and their knowledge about Avogadro s number to explain, in their science notebooks, how the values for their mole label were determined. 7. Instruct student pairs to check each other s work. Facilitate as necessary, and help students resolve any questions about mole label determinations. 8. Monitor student progress and facilitate as needed. Instruct pairs to check in with you when they finish their analyses. 9. As student pairs complete their analyses, assign the pair another substance from the list provided in the Teacher Resource: Mole Labels. 10. When the majority of students are finished, call on pairs of students to present their label explanations. Continue this process so that all six substances are explained. 11. Facilitate a discussion of key concepts using the following questions as a guide. What is Avogadro s number? 6.02 x 10 23 How is the mole defined in terms of mass and particles? The mole is the mass of Avogadro s number of particles, 6.02 x 10 23. How is the mass of one mole of an element calculated? By using the Periodic Table atomic mass for that element Note: students will learn the diatomic elements later. How is the mass of one mole of a compound calculated? By adding the respective atomic masses from the Periodic Table for each element based on the chemical formula for substance. This is called the molar mass of the substance. How is molar mass used to calculate the number of moles in any given mass of an element, compound, or ionic substance? one-mole containers (see Advance Preparation, 2 sets per class): sodium chloride (58.5 g) water (18 ml) sucrose (342 g) copper (63.5 g) aluminum (27 g) oxygen (room temperature air, about 24.5 L) periodic table from STAAR Reference Materials (1 per student) scientific calculators (1 per student) Teacher Resource: Mole Labels (see Advance Preparation, 1 per set) Instructional Notes: At room temperature, a mole of any gas will occupy about 24.5 L. This can be modeled a variety of ways (see Advance Preparation). Be sure to use mol as the symbol so students get accustomed to it. Check for Understanding: Today s opening activity is designed to give students an understanding of the concept of molar mass. They should see that this is different for each substance. Students record analyses of their mole labels in their notebooks. 2012, TESCCC 05/07/13 page 7 of 10
Dividing the given mass by the molar mass equals the number of moles How is Avogadro s number used to calculate the number of representative particles in one mole of an element or a compound? Multiplying the number of moles times 6.02 x 10 23 equals the number of representative particles. How is Avogadro s number used to calculate the number of representative particles in any given mass of an element or compound? Dividing the given mass by the molar mass and then multiplying the result (number of moles) by 6.02 x 10 23 equals the number of representative particles. 12. Use locally adopted resources to provide a few more examples for students to practice calculating molar masses and atoms. EXPLORE/EXPLAIN IV Matters of Matter Solids Suggested Day 4 1. Explain that today students will be collecting data and doing mole calculations. Arrange students into pairs. 2. Distribute a copy of the Handout: Matters of Matter Solids to each pair. Ask students to read the instructions, and answer any questions they may have. 3. Instruct students to take measurements, complete their data tables in pairs, and then compare their results with the results of another pair of students. 4. Monitor the calculations of moles of sample and number of representative particles in the data table. 5. Ensure teams have calculated their molar masses correctly, especially sucrose. 6. As teams finish their data tables, have them complete the Analysis section of the activity and then compare with their table partners. 7. As needed, provide and/or work sample problems to change from mass to moles and moles to mass. electronic balance (1 per group) sodium chloride (~1 spoonful per group) sucrose (~1 spoonful per group) aluminum pieces (~1 spoonful per group) plastic spoons (1 per group) Handout: Matters of Matter Solids (1 per pair) Teacher Resource: Matters of Matter Solids KEY Instructional Notes: Students should now understand that the number of representative particles in a given number of moles of any substance is the same, but the mass of the given number of moles of each substance is different. Depending on the level of the class, students should be required to use dimensional analysis in solving all problems. Students record data and calculations in their notebooks. 2012, TESCCC 05/07/13 page 8 of 10
EXPLORE/EXPLAIN V Matters of Matter Pure Liquids Suggested Day 5 1. Display and identify labeled containers of one mole each of three pure liquids: water (~18mL), isopropyl alcohol (~23mL), and hydrogen peroxide (~77mL). Label each with name, formula, and 1 mol (see Advance Preparation). Note: These are really three containers of water representing the three pure liquids. 2. Distribute a copy of the Handout: Matters of Matter Pure Liquids to each student. Students will work with the same partner as the previous day. 3. Facilitate a discussion in which students review density, and remind students how volume and density can be used to determine the mass of a given volume of a pure liquid. 4. Direct students to find the density formula on the STAAR Chemistry Reference Materials document under the heading Other Formulas. 5. Ask student pairs to work through the handout. Monitor progress, and answer questions as needed. labeled containers of liquids (see Advance Preparation, per teacher) glue or tape (per group) Handout: Matters of Matter Pure Liquids (1 per student) Teacher Resource: Matters of Matter Pure Liquids KEY Handout: Mole Potpourri (1 per pair) Teacher Resource: Mole Potpourri KEY 6. Point out that mercury was added to the data table, but not displayed due to safety concerns. 7. Remind students to show appropriate units and to use dimensional analysis. 8. Monitor and assist students as necessary. 9. Review the handout calculations and analysis with students using a shoulder partner or other appropriate sharing method. 10. Distribute a copy of the Handout: Mole Potpourri to each pair of students. Instruct students work in teams to complete the handout and to compare answers with each other. 11. Discuss any questions students may have regarding the handout. Include the following questions in the discussion: Who can state the formula for density? Density is mass per unit volume: D = m/v. How are density, volume, and mass related to moles and representative particles? Density is mass per unit volume: D = m/v. Volume and density are used to determine mass. Mass divided by molar mass then equals moles, which can be converted to representative particles using Avogadro s number. 12. Instruct students to affix their handouts in their notebooks. Check for Understanding: Evaluate student understanding of the mole concept using a sharing out or another strategy before asking them to work on the Mole Potpourri handout. Instructional Notes: Water is used to represent pure samples of isopropyl alcohol and hydrogen peroxide. These substances from a store will not be 100%. In addition, 100% hydrogen peroxide is dangerous. So, you will be faking these two. Make labels that correspond to the selected examples. Students should be able to use the concept of density to determine the mass of a pure liquid in a given volume. At this point in the lesson, students should be able to do the following: convert particles to moles and moles to particles convert mass to moles and moles to mass convert particles to mass and mass to particles convert volume to mass using the density formula 2012, TESCCC 05/07/13 page 9 of 10
Students record calculations and complete answers to questions in their science notebooks. ELABORATE Mole Day Celebration Suggested Days 6 and 7 1. Inform students you want to have a classroom display of moles to celebrate National Mole Day at the end of the unit, much like you showed them during the ENGAGE activity. 2. Next, ask students to brainstorm some common household materials and the element, ionic, or molecular compound each household material represents. For example: toothpaste could be used to represent stannous fluoride (SnF 2), nails could represent iron (Fe), and a salt shaker could be sodium chloride (NaCl). 3. Assign groups the challenge of selecting and then presenting to the class a mole of an element or compound (ionic or molecular) of their choice in a labeled container. NOTE: Access to the Internet and empty containers of household materials are helpful resources to determine what element or compound a chosen material might represent. 4. Provide each student/team a blank label to use for their mole container. 5. As homework, instruct students/teams to collect their materials at home and bring them to school in appropriate containers. Discuss safety precautions for allowing any containers that might still contain substances that might pose safety concerns. 6. Additionally, ask students to briefly research the history Avogadro s number (see Instructional Note). You may wish to have students write the information in a paragraph or two in their science notebooks. 7. On Day 7, instruct each group to mass one mole of material using a balance in class and then label their container with the name, formula, and molar mass. 8. Conclude your Mole Day celebration with a gallery walk/display of your new moles. Note: Check the Mole Day website for many other ideas for Mole Day activities. Additionally, ask students to share the information they researched on Avogadro s number. labels (2 x3, 1 per student) electronic balance (1 per group) household materials, empty containers (for Mole Day examples, per teacher) Instructional Notes: National Mole Day is celebrated annually from 6:02 AM to 6:02 PM on October 23. Since this date probably won t occur in conjunction with the implementation of this unit, you may choose to celebrate a School Mole Day. Display the date in your classroom, and if you can, find and play Mole Day music. NOTE: You may want to keep their mole containers for future use. Professor Lorenzo Romano Amedeo Carlo Avogadro, 1776-1856, was the Italian physicist honored posthumously for his pioneering work. He did not determine Avogadro s number. Rather, it was named after him by French physicist Jean Perrin in his honor. Perrin won the 1926 Nobel Prize in physics, in large part for his work in determining Avogadro s number by a variety of methods. Students record information on Avogadro s number. EVALUATE Performance Indicator Suggested Days 7 (continued) and 8 Performance Indicator Given the cost and area of a roll of aluminum foil, plan and implement an investigation to determine the cost of a single atom of Al. Record all 2012, TESCCC 05/07/13 page 10 of 10
assumptions, procedures, data, and calculations in your science notebook. Summarize how Avogadro s number and molar mass were used. (C.2E, C.2F, C.2G, C.2I; C.8A, C.8B) 1C; 3F; 5G 1. Refer to the Teacher Resource: Performance Indicator Instructions KEY and the Handout: Foiled Again PI for information on administering the assessment. aluminum foil (20 x 20 cm, see Advance Preparation, 1 piece per student) electronic balance (1 per group) ruler (metric, 1 per student) Handout: Foiled Again PI (1 per student) Teacher Resource: Foiled Again PI KEY Teacher Resource: Performance Indicator Instructions KEY 2012, TESCCC 05/07/13 page 11 of 10