Science Grade 08 Unit 10 Exemplar Lesson 01: Light Years and Origins of the Universe

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1 Unit: 10 Lesson: 01 Suggested Duration: 5 days Grade 08 Unit 10 Exemplar Lesson 01: Light Years and Origins of the Universe This lesson is one approach to teaching the State Standards associated with this unit. Districts are encouraged to customize this lesson by supplementing with district-approved resources, materials, and activities to best meet the needs of learners. The duration for this lesson is only a recommendation, and districts may modify the time frame to meet students needs. To better understand how your district may be implementing CSCOPE lessons, please contact your child s teacher. (For your convenience, please find linked the TEA Commissioner s List of State Board of Education Approved Instructional Resources and Midcycle State Adopted Instructional Materials.) Lesson Synopsis In this lesson, students will model and describe how light years are used to measure vast distances in space. Students will develop a scale drawing that represents the comparative distances in light years between three objects in the universe and include a statement discussing the advantages and limitations of using a scale drawing to represent large distances. Secondly, students will research scientific theories of the origin of the universe and develop a timeline including scientists and their supporting evidence. TEKS The Texas Essential Knowledge and Skills (TEKS) listed below are the standards adopted by the State Board of Education, which are required by Texas law. Any standard that has a strike-through (e.g. sample phrase) indicates that portion of the standard is taught in a previous or subsequent unit. The TEKS are available on the Texas Education Agency website at id=6148. Scientific Process TEKS 8.8 Earth and space. The student knows characteristics of the universe. The student is expected to: 8.8D Model and describe how light years are used to measure distances and sizes in the universe. Supporting Standard 8.8E Research how scientific data are used as evidence to develop scientific theories to describe the origin of the universe. 8.2 Scientific investigation and reasoning. The student uses scientific inquiry methods during laboratory and field investigations. The student is expected to: 8.2C Collect and record data using the International System of Units (SI) and qualitative means such as labeled drawings, writing, and graphic organizers. 8.3 Scientific investigation and reasoning. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions and knows the contributions of relevant scientists. The student is expected to: 8.3A In all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student. 8.3B Use models to represent aspects of the natural world such as an atom, a molecule, space, or a geologic feature. 8.3C Identify advantages and limitations of models such as size, scale, properties, and materials. 8.3D Relate the impact of research on scientific thought and society, including the history of science and contributions of scientists as related to the content. 8.4 Scientific investigation and reasoning. The student knows how to use a variety of tools and safety equipment to conduct science inquiry. The student is expected to: 8.4A Use appropriate tools to collect, record, and analyze information, including lab journals/notebooks, beakers, meter sticks, graduated cylinders, anemometers, psychrometers, hot plates, test tubes, spring scales, balances, microscopes, thermometers, calculators, computers, spectroscopes, timing devices, and other equipment as needed to teach the curriculum. GETTING READY FOR INSTRUCTION Performance Indicators Last Updated 05/14/13 page 1 of 17

2 Grade 08 Unit 10 PI 01 Make a timeline for discoveries relating to the understanding of the origins of the universe. Include relevant scientists and their supporting evidence. Standard(s): 8.3A, 8.3D, 8.8E ELPS ELPS.c.1C, ELPS.c.5B, ELPS.c.5D Grade 08 Unit 10 PI 02 Develop a scale drawing that represents the comparative distances in light years between three objects in the universe. Include a statement discussing the advantages and limitations of using a scale drawing to represent large distances. Standard(s): 8.2C, 8.3B, 8.3C, 8.8D ELPS ELPS.c.1C, ELPS.c.5B, ELPS.c.5G Key Understandings Light years are units of time used to measure the distance between objects in the universe. Why is a light year a unit of distance rather than time? Why do we need to use light years as a way of measuring cosmic distances? What is the speed of light? How are light years used to measure distances in the universe? There are several theories regarding the creation of the universe. What is a theory? What is the theory of the Big Bang? Why do some scientists believe that the universe is expanding? Evidence gathered from the past is used to explain the universe and help predict the future. Why do scientists revise theories? Vocabulary of Instruction Unit: 10 Lesson: 01 Suggested Duration: 5 days light year (ly) Big Bang theory theory speed of light Materials colored pencils or markers glue or tape (per class) meter stick (1 per group) paper (butcher, various colors, multiple per class) pencil (unsharpened, 1 per group) rulers (1 per student) string or yarn (ball per group) Attachments All attachments associated with this lesson are referenced in the body of the lesson. Due to considerations for grading or student assessment, attachments that are connected with Performance Indicators or serve as answer keys are available in the district site and are not accessible on the public website. Teacher Resource: PowerPoint: Light Year (see Advance Preparation) Handout: Light Year Model PI (1 per student and 1 for projection) Teacher Resource: Light Year Model KEY Teacher Resource: Performance Indicator Instructions 01 KEY (1 for projection) Handout: Big Bang Research Organizer (see Advance Preparation, 1 per student and 1 for projection) Teacher Resource: Theory Selection Cards (see Advance Preparation, 1 card per student) Handout: Resource Organizer (1 per student) Handout: Research Sharing Organizer (1 per student) Teacher Resource: Performance Indicator Instructions 02 KEY (1 for projection) Last Updated 05/14/13 page 2 of 17

3 Resources Unit: 10 Lesson: 01 Suggested Duration: 5 days None Identified Advance Preparation 1. Prior to Day 1: Print the slide notes from the Teacher Resource: PowerPoint: Light Year for reference during the class discussion. Perform a web search for an approved site on astronomical distances. (You may find it helpful to include the terms janus astronomical distances in your search.) Input some ages, and view how long it would take to arrive. This will help students develop some perspective on the concept. 2. Prior to Day 3: Print on cardstock, laminate, and cut apart the Teacher Resource: Theory Selection Cards, and place them in a bag. There are ten different theories. You will need one theory card per student. Arrange for student computer/internet use for Days 3, 4, and 5. Locate and preview approved resources for student research including websites, books, periodicals, etc. Specify and label 11 locations for each theory for the gallery walk. 3. Prepare attachment(s) as necessary. Background Information This lesson bundles student expectations that address how to measure distances in space and how they are measured by using light waves. In addition, students will conduct research on scientific theories of the origin of the universe. Prior to this unit, students have had little exposure to light years or theories on the origin of the universe. During this lesson, students look at scientific theories used to describe the origin of the universe. They also describe how light years are used to measure distances and sizes in the universe. Using light years to express astronomical distances is not an easy concept for students to understand. Students may think of light years as a measure of time. They also may have difficulty relating to the very large distances involved in space. After this unit, in, students will study how the electromagnetic spectrum is used to gain information about distances and properties of components in the universe. They will also describe components of the universe. NOTE: The curriculum in this CSCOPE unit is based upon the Texas Essential Knowledge and Skills (TEKS), which are the teaching standards required under the provisions of the Texas Education Code. During the course of instruction, students may voice diverse viewpoints regarding the topic of the origin of the universe. Educators are encouraged to consult with district administration to determine how they should best address these varying perspectives so that all viewpoints are respected and district expectations are met. STAAR Note: Modeling and describing how light years are used to measure distances and sizes in the universe (8.8D) will be assessed as a Supporting Standard under Reporting Category 3: Earth and Space on the STAAR Assessment. INSTRUCTIONAL PROCEDURES Instructional Procedures ENGAGE Measuring Distance Notes for Teacher NOTE: 1 Day = 50 minutes Suggested Day 1 1. Project or write the following speed terms on the board: a. mph b. knots c. mach d. speed of light e. warp 2. Ask for student volunteers to describe what the terms measure. Acknowledge all responses. 3. The following list is in the same order as the list above. Write these answers beside the above list: a. miles traveled per hour b. nautical miles traveled in an hour (One nautical mile is equal to Last Updated 05/14/13 page 3 of 17

4 miles.) Unit: 10 Lesson: 01 Suggested Duration: 5 days 4. Ask/Say: c. an object's speed divided by the speed of sound d. the speed of all electromagnetic waves (approximately 300,000 km/s) e. doesn t exist, except on Star Trek speed faster than the speed of light How are these terms similar? Acknowledge responses. Students should note that measurement is a commonality. In this unit, one way we measure great distances will be explored light years. Circle the term, light years. EXPLORE/EXPLAIN Measuring 1. Inform students that they are going to work in pairs to measure distances in the classroom using the following measuring tools: 1 unsharpened pencil 1 12 inch ruler 1 meter stick string or yarn Suggested Day 1 (continued) Materials: pencil (unsharpened, 1 per group) ruler (1 per group) meter stick (1 per group) string or yarn (ball per group) 2. Instruct students to use the yarn to measure distances from: (Demonstrate as you explain.) the classroom door to a student desk to the teacher desk to 3. The yarn s distance can then be measured with each of the measuring tools (pencil, ruler, meter stick, and yarn). 4. Instruct students to design a data table, collect data, and record measurements in their science notebooks. A sample is shown below. Attachments: Teacher Resource: PowerPoint: Light Year (see Advance Preparation) Instructional Notes: Print the notes version of the Power Point to present additional information on most of the slides. Students may not be familiar with the idea of a vacuum in space. Misconception: Students may think that a light year is a measure of time. 5. Answer any questions students may have regarding the task. 6. Divide the class into pairs, and distribute all materials. 7. Monitor students while they measure and assist as necessary. Address any measurement misconceptions as you observe. 8. Facilitate a discussion in which students reflect on the following questions. Ask: Which units are best to describe the distances of objects to the teacher s desk? Answers may vary, depending on distance. Which unit was not appropriate for describing the farthest distance? Why? Pencil, difficult to use What measurement unit would be used to measure from the teacher s desk to your home? (Kilometers) Students may answer in miles because they do not have a visual idea of km. What measurement could be used to measure from the teacher s desk to the next city? To the Moon? Hundreds or thousands of kilometers STAAR Note: Modeling and describing how light years are used to measure distances and sizes in the universe (8.8D) will be assessed as a Supporting Standard under Reporting Category 3: Earth and Space on the STAAR Assessment. Check For Understanding: The reflective questions may be used as an informal assessment. Notebooks: Students create data tables, record data and vocabulary, and answer reflective questions in their notebooks. Last Updated 05/14/13 page 4 of 17

5 What if we have to measure vast distances from Earth to another galaxy? Could we use centimeters, meters, kilometers, miles, and feet? Yes, we could use those units, but it wouldn t be reasonable. The numbers would be extremely large. What type of measuring unit would we need for distances across space? Answers may vary, as students haven t studied light years yet. They may say km or light years. Unit: 10 Lesson: 01 Suggested Duration: 5 days 9. Project the Teacher Resource: Power Point: Light Year. Present additional information found on the notes view of the PowerPoint to students. Continually reinforce that a light year is a unit to measure distance, not time. 10. Instruct students to take notes in their notebooks during the PowerPoint discussion. Students should record the definition of light year and any relevant information. 11. Project a teacher selected website on astronomical distances (see Advance Preparation). 12. Following the PowerPoint and website exploration, ask students to work with a partner to reflect on the following questions in their notebooks. Ask: Why is a light year a unit of distance rather than time? It measures the distance light travels in a vacuum in one year trillion km or trillion miles. Why do we need to use light years as a way of measuring cosmic distances? If we used conventional measurements, the numbers would be huge and difficult to calculate. What is the speed of light? The rate at which light travels through empty space - 299,792,458 meters/second or 186,000 miles/second. How are light years used to measure distances in the universe? If we know how fast light can travel from a particular distance (the Sun), we can apply this to other objects in our universe. ELABORATE/EVALUATE Performance Indicator 01 Suggested Day 2 Grade 08 Unit 10 PI 02 Develop a scale drawing that represents the comparative distances in light years between three objects in the universe. Include a statement discussing the advantages and limitations of using a scale drawing to represent large distances. Standard(s): 8.2C, 8.3B, 8.3C, 8.8D ELPS ELPS.c.1C, ELPS.c.5B, ELPS.c.5G 1. Refer to Teacher Resource: Performance Indicator Instructions 01 KEY for information on administering the performance assessment. Materials: rulers (1 per student) colored pencils (per student) Attachments: Handout: Light Year Model PI (1 per student and 1 for projection) Teacher Resource: Light Year Model KEY Teacher Resource: Performance Indicator Instructions 01 KEY (1 for projection) EXPLAIN Big Bang Research Suggested Day 3 1. Present the following questions to the class. Instruct students to record the answers to these questions in their notebooks as you facilitate a discussion on the Big Bang theory. Ask/Say: What is a theory? Theories are the most accepted explanation- based on information from research. What is the theory of the Big Bang? (Students may have no prior knowledge of this theory.) This theory is based on the observation that other galaxies are moving away from our Milky Way galaxy at great speeds in all directions. Materials: Attachments: glue or tape (per group) Handout: Big Bang Research Organizer (see Advance Preparation, 1 per student and 1 for projection) Last Updated 05/14/13 page 5 of 17

6 Why do some scientists believe that the universe is expanding? It is based on the idea that galaxies are moving away from us. Why do scientists revise theories? Theories can change if the evidence supports the change. 2. Project the Handout: Big Bang Research Organizer, and explain the expectations for the research activity to students (see Advance Preparation). 3. Answer any questions students may have. 4. Distribute the Handout: Big Bang Research Organizer to each student. Allow students to read the information on the handout. 5. Say: Theories are the most accepted explanation, based on information from research. Theories can change if the evidence supports the change. While the Big Bang theory is the most popular and widely accepted theory about the beginnings of the universe and supported by all the observational evidence, there are other theories that explain the evidence equally well. But, until further evidence supports a change, this theory is the currently accepted one. You will be researching one of 10 other theories. This handout models the information you will need to gather. You may summarize the information about the description of the theory and the evidence, but try to find all the types of information listed on the sample. Please do NOT plagiarize. Paraphrase information in your own words. Instructional Notes: Students will use Handout: Big Bang Research Organizer (see Advance Preparation) as a model for their theory research. NOTE: The curriculum in this CSCOPE unit is based upon the Texas Essential Knowledge and Skills (TEKS), which are the teaching standards required under the provisions of the Texas Education Code. During the course of instruction, students may voice diverse viewpoints regarding the topic of the origin of the universe. Educators are encouraged to consult with district administration to determine how they should best address these varying perspectives so that all viewpoints are respected and district expectations are met. Misconception: Students may think that there was a huge explosion, rather than rapid expansion, that began the solar system, galaxies, and the universe. Notebooks: Students record vocabulary, answer questions, and affix the Handout: Big Bang Research Organizer. Unit: 10 Lesson: 01 Suggested Duration: 5 days 6. Instruct students to affix the Handout: Big Bang Research Organizer to their notebooks. EXPLORE/EXPLAIN Theory Research Suggested Days 3 (continued) and Day 4 1. Allow students to select a Theory Selection Card (see Advance Preparation) from the bag of cards prepared prior to class. 2. Once students have selected their theory, distribute the Handout: Resource Organizer to each student. Refer students back to the Big Bang Research Organizer to remind them how to complete the information requested. Additionally, remind them that they will need to compare the Big Bang theory to the other theories researched. 3. Monitor and assist as students complete their research. You may wish to group students in pairs to accommodate access to computers. 4. When students have completed their research, instruct them to post their research in a specified location for their selected theory (see Advanced Preparation). Be sure to display the Big Bang Research Organizer as well. 5. Explain the procedure for a gallery walk to collect information on other theories. There will be 11 theories posted. If a group is at a theory that one of the group members researched, they will explain it to the others. 6. Answer any questions students may have about the gallery walk. 7. Distribute the Handout: Research Sharing Organizer to each student. 8. Divide the class into groups of 2 3, and allow them to rotate through the gallery walk at your signal. 9. Monitor students as they rotate to ensure they are recording accurate information. 10. Instruct students to answer the question at the bottom of the chart individually, not as a group. Answers will vary, as this is student opinion based on the research presented. There is no correct or incorrect answer (see Instructional Notes). Attachments: Teacher Resource: Theory Selection Cards (see Advance Preparation, 1 card per student) Handout: Research Organizer (1 per student) Handout: Research Sharing Organizer (1 per student) Instructional Notes: Answers to the final question will vary, as this is student opinion (not necessarily their beliefs) based on the research presented. There is no correct or incorrect answer. Make sure students are fully aware of this as the origin of the universe discussion may be a sensitive topic in some communities and student viewpoints should be respected. Consider providing partially completed or more structured templates for students who require differentiation with writing tasks. Notebooks: Students affix the Handout: Research Sharing Organizer. Last Updated 05/14/13 page 6 of 17

7 Unit: 10 Lesson: 01 Suggested Duration: 5 days 11. Instruct students to affix the organizer in their notebooks. ELABORATE/EVALUATE Performance Indicator 02 Suggested Day 5 Grade 08 Unit 10 PI 01 Make a timeline for discoveries relating to the understanding of the origins of the universe. Include relevant scientists and their supporting evidence. Standard(s): 8.3A, 8.3D, 8.8E ELPS ELPS.c.1C, ELPS.c.5B, ELPS.c.5D 1. Refer to Teacher Resource: Performance Indicator Instructions 02 KEY for information on administering the performance assessment. Materials: paper (butcher, various colors, multiple per class) colored pencils or markers (per pair) ruler (1 per pair of students) glue or tape (per class) Attachments: Handout: Research Organizer (previously distributed) Handout: Research Sharing Organizer (previously distributed) Teacher Resource: Performance Indicator Instructions 02 KEY (1 for projection) Last Updated 05/14/13 page 7 of 17

8 Light Year Model PI Unit: 10 Lesson: 01 Relatively Close Objects Sun Scale: 1 light year =.5 cm Directions: 1. Develop a scale drawing that represents the comparative distances in light years between the following three objects in the universe: Proxima Centauri (4 light years away) Sirius (9 light years away) Solar Neighborhood (33 light years away) 2. Write a statement discussing the advantages and limitations of using a scale drawing to represent large distances. Use a scale of 1 light year =.5 cm Your diagram should include both an illustration and labels. 2012, TESCCC 05/13/13 page 1 of 1

9 Light Year Model KEY Unit: 10 Lesson: 01 Relatively Close Objects Sun Proxima Centauri Sirius Solar Neighborhood (4 ly) (9 ly) (33 ly) Scale: 1 light year =.5 cm Directions: 1. Develop a scale drawing that represents the comparative distances in light years between the following three objects in the Universe: Proxima Centauri (4 light years away) Sirius (9 light years away) Solar Neighborhood (33 light years away) Use a scale of 1 light year =.5 cm Your diagram should include both an illustration and labels. 2. Write a statement discussing the advantages and limitations of using a scale drawing to represent large distances. Advantages A scale drawing is used so that relative sizes are correctly represented. The scale is chosen both to ensure the whole system will fit on the specified paper and to show the required amount of detail. When you are trying to visualize something that is REALLY BIG, sometimes it is helpful to build a scale model. In a scale model, we make everything smaller by the same proportional amount. Limitations In a scale model, you can usually only focus on one aspect of the model at a time. For example, you could make a model to represent distance, or you could make a model to represent size, but it is a challenge to make a model that accurately represents both. 2012, TESCCC 10/25/12 page 1 of 1

10 Performance Indicator Instructions 01 KEY Unit: 10 Lesson: 02 Performance Indicator Develop a scale drawing that represents the comparative distances in light years between three objects in the universe. Include a statement discussing the advantages and limitations of using a scale drawing to represent large distances. (8.2C; 8.3B, 8.3C; 8.8D) 1C; 5B, 5G Materials: rulers (1 per student) colored pencils (per student) Attachments: Handout: Light Year Model PI (1 per student and 1 for projection) Teacher Resource: Light Year Model KEY Instructional Procedures: 1. Project the Handout: Handout: Light Year Model PI, and present the expectations to students. 2. Distribute the Handout: Light Year Model PI to each student. 3. Monitor and assist students as necessary. 2012, TESCCC 05/13/13 page 1 of 1

11 Big Bang Research Organizer Sample Unit: 10 Lesson: 01 Sources: Use appropriate resources such as the Internet, encyclopedias, books, journals, etc. Cite each source by the name and date of the periodicals or website. You must use at least two resources. See your teacher for approved websites and resources. URL of website and date retrieved Name of periodical and date of publication Name of book and copyright date Name of Theory: Big Bang Theory 1927 Scientist(s) Responsible for Theory: Georges Lemaître, a Belgian priest, was the first to theorize that the universe came from a single atom. Albert Einstein s theory of relativity added to this idea. Observations that galaxies are moving away from our own galaxy were made by Edwin Hubble. Cosmic microwave radiation was discovered by Arno Penzias and Robert Wilson. Pictorial Representation or Sketch of Theory: (cite images) Description of Theory: The most well-known theory of the origin of our universe is the Big Bang theory. The universe is thought to have originally consisted of a very small volume with very high density and high temperatures. The idea comes from observations that galaxies are moving away from our own. The phenomena is compared to an explosive force, hence Big Bang. The Big Bang theorizes that space itself began expanding like the surface of an inflating balloon. The Big Bang is not like an explosion of matter. It carried matter with it as it expanded. There was no explosion; only an expansion that still continues. Imagine an extremely tiny balloon expanding to the size of our current universe. Evidence to Support Theory: The universe had a beginning. Most galaxies are moving away from us. This is called "Hubble's Law", named after Edwin Hubble ( ). If the universe was very hot in the beginning, there should be some evidence of this heat. Cosmic microwave radiation was discovered in 1965 by radio astronomers Arno Penzias and Robert Wilson. The large amount of hydrogen and helium found in the universe. 2012, TESCCC 05/14/13 page 1 of 1

12 Theory Selection Cards Unit: 10 Lesson: 01 Flat Earth Theory Flat Earth Theory Flat Earth Theory Flat Earth Theory Ptolemy Universe Theory Ptolemy Universe Theory Ptolemy Universe Theory Ptolemy Universe Theory Copernicus Universe Theory Copernicus Universe Theory Copernicus Universe Theory Copernicus Universe Theory Kepler s Universe Theory Kepler s Universe Theory Kepler s Universe Theory Kepler s Universe Theory Steady State Universe Theory Steady State Universe Theory Steady State Universe Theory Steady State Universe Theory Friedmann Universe Theory Friedmann Universe Theory Friedmann Universe Theory Friedmann Universe Theory Anthropic Universe Theory Anthropic Universe Theory Anthropic Universe Theory Anthropic Universe Theory Inflationary Universe Theory Inflationary Universe Theory Inflationary Universe Theory Inflationary Universe Theory No Boundary Universe Theory No Boundary Universe Theory No Boundary Universe Theory No Boundary Universe Theory Oscillating Universe Theory Oscillating Universe Theory Oscillating Universe Theory Oscillating Universe Theory 2012, TESCCC 10/25/12 page 1 of 1

13 Research Organizer Unit: 10 Lesson: 01 Sources: Use appropriate resources such as the Internet, encyclopedias, books, journals, etc. Cite each source by the name and date of the periodical or website. You must use at least two resources. Name of Theory: Scientist(s) Responsible for Theory: Pictorial Representation or Sketch of Theory: Description of Theory: 2012, TESCCC 10/25/12 page 1 of 1

14 Research Sharing Organizer Unit: 10 Lesson: 01 Name of Theory: Big Bang (Refer to the handout affixed to your notebook.) Name of Theory: Name of Theory: Name of Theory: 2012, TESCCC 10/25/12 page 1 of 3

15 Name of Theory: Name of Theory: Unit: 10 Lesson: 01 Name of Theory: Name of Theory: 2012, TESCCC 10/25/12 page 2 of 3

16 Name of Theory: Name of Theory: Unit: 10 Lesson: 01 Including the Big Bang theory and theories researched, which is the most reasonable theory to you? Explain your reasoning. (There is no right or wrong answer to this question, as this is your opinion.) 2012, TESCCC 10/25/12 page 3 of 3

17 Performance Indicator Instructions 01 KEY Unit: 10 Lesson: 02 Performance Indicator Make a timeline for discoveries relating to the understanding of the origins of the universe. Include relevant scientists and their supporting evidence. (8.3A, 8.3D; 8.8E) 1C; 5B, 5D Materials: paper (butcher, various colors, multiple per class) colored pencils or markers (per pair) ruler (1 per pair of students) glue or tape (per class) Handout: Research Organizer (previously distributed) Handout: Research Sharing Organizer (previously distributed) Instructional Procedures: 1. Present the expectations of the Performance Indicator to the students, and answer any questions they may have. 2. Using the Research Organizer and Research Sharing Organizer affixed in notebooks from the previous day, students are to construct a timeline for discoveries for the origins of the universe. Include the following: theory, date, scientist(s), and evidence. Remind students to include the Big Bang theory as a part of their timelines. 3. Divide the class into pairs to complete the activity. 4. Monitor groups, and assist as necessary. 2012, TESCCC 05/13/13 page 1 of 1