Unit 1.3: Units and Conversions

By the end of this unit, students will be able to:

• Practice using units of time and energy to explain the value of standard units of measurement and simple conversions for the practice of science
• Express the dimensions of an object as a whole number of length units

This unit combines a lecture setting and an extension lab activity and is suitable for populations of students that do not have much exposure to scientific units and who likely find unit conversions very challenging. No prior unit conversion experience is assumed or necessary. Plan for these materials to take about 50 min of class time (add 55-70 min if the Measuring Sticks Extension Lab is completed).

These materials could be adapted to all class types (large/small, in person/remote, synchronous/asynchronous). However, they are written assuming an in-person synchronous classroom. For a large in-person course, the Measuring Sticks lab will likely be very loud. It is not necessary that the two activities (labeled Part 1 and Part 2 below) are completed in order - these activities are complimentary, but they do not necessarily build on each other.

Teaching Materials:

All Slides: U1.3 All Slides.pptx (PowerPoint 2007 (.pptx) 7.7MB Jul8 24)

Conversion Factors Student Handout:

• doc: Unit 1.3 Conversion Factors Student Handout v2 (Microsoft Word 2007 (.docx) 109kB Aug30 24)
• pdf: u1.3_conversion_factors_handout.pdf (Acrobat (PDF) 102kB Jul15 24)

Measuring Sticks Lab:

• Student Handout: U1.3 Measuring Sticks Worksheet.docx (Microsoft Word 2007 (.docx) 260kB Jul16 24)
• Sample Student Responses - for Instructors:
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• Materials: A collection of materials that have different sizes. You might try the following:
  • Paper clips (full boxes of consistent size clips, can have boxes of different sizes, but need many of same size for each group of students)
  • Toothpicks
  • Popsicle sticks and/or tongue depressors
  • Colored pencils or wax crayons (new not necessary, random sizes encouraged)

Other materials: differently colored dry-erase markers and a whiteboard.

Pre-class Assignment(s):

Answers to discussion questions should be submitted (online via LMS or with another tool, instructor's preference). Both of these questions are addressed as part of the slides:

• Read "Unit Conversion" (Visionlearning).
• There are three steps, outlined in the reading, for performing a unit conversion calculation. What are they?
• Calculate how many seconds in one day in a way that makes sense to you (try to do it using conversion factors if you can). Show your work/explain your thinking.

In Class Part 1: Units, Unit Conversions, and Conversions Factors (50 min)

Introduction (20 min):

• Consider the headline: "Tonga Undersea Volcano Eruption Released 18 Megatons of Energy, Scientists Say." Discussion questions:
  • What does this headline tell you? What does it NOT tell you? Does anyone here know what a "megaton" is? What if I told you that "megaton" is short for "megatons of TNT." Do you know what that means now? Are there still things you don't know?
  • Note: Hunga Tonga's eruption is the motivating question for the upcoming Unit 2 on Energy.
• Without units, numbers are meaningless. We use units to compare numbers in useful ways, and we need a common set of units to describe phenomena.
• Scientific units may be unfamiliar, but they are the same principle as everyday units. It makes sense to describe the energy in a volcanic eruption differently compared to the energy in a snack.
• Develop a list of all the different units we use in everyday life (on the board, color-coded by category)
  • Energy is coming up next in Unit 2, so spend some extra time on the units of energy: connect Joules with everyday units of energy like Calories (food), kWh (electronics), megatons of TNT (volcanoes - not a common unit).

Practice using Conversions Factors (30 min):

• Consider two conversion factor problems: How many seconds are in a day? How many hours could a Snickers candy bar power a light bulb? Present a variety of other conversion problems with increasing difficulty so that students can challenge themselves (remember to challenge your students to work on their growth mindset: work on something hard/interesting, not necessarily something you're confident you can do ). Revisit the pre-class discussion questions.

Wrap Up (5 min):

• Where we've finished: Units are useful, must use units that make sense, need a common language that is relatable. Used time as a way to set up conversion factors since you already know those conversion factors (60 seconds = 1 minute). Moved into energy - same strategy, less intuitive.

In Class Part 2: Measuring Sticks Extension Lab (55-85 min)

Introduction (5 min):

• Discuss learning goals and expectations for the science journal. These graded journals will be completed for every lab activity in the course. If the Bubbles Lab was completed in Unit 1.2, then discuss what was done well/what could use improvement from that. If the Bubbles Lab wasn't completed in Unit 1.2, then this is the students' first science journal. Make sure to discuss expectations. Note: an optional handout is included to use in lieu of science journals for classes short on time.

Hypothesis and Experimentation (40-60 min):

• This activity challenges students to develop a system for basic measurement, use it successfully, and teach it to others such that they can use it successfully. This activity is designed to provide context for basic units of measurement and unit conversions. Students will be able to reason why the metric system is base 10 and what is the meaning of "unit conversion."
  • Split the class into groups and give each group the same materials. If there are 3 in a group, give them 3 of the 4 items, that is, each group should have 1 material per person (one box of paper clips, one box of used crayons, etc.).
  • Challenge the students to devise a measurement system using these materials. They must try to develop a way to consistently measure something (e.g. the width of the desk, the height of a chair, some other random thing) using the materials they have been provided. Provide the following guiding questions:
    • How will each material "unit" relate to the others?
    • Will one be a "master unit material"?
    • Will you use all the materials or will you decide not to use one; and if so, why?

The goal is to develop a system of measurement that they can teach another group to use such that they can successfully measure the same object, and get the same value, that the group who developed it did.

Follow-up discussion questions (10-20 min):          

• Did you subdivide materials into regular lengths?
  • If so, how many divisions and why?
  • If not why not?
• What methods did you try that were unsuccessful?
  • Why did you find them to be unsuccessful? 
  • Did other groups have similar challenges?
• What methods did you try that were successful?
  • Why did you find them to be successful? 
  • What strategies did other groups use that you wish you had tried?
• Would it be possible to combine your measurement systems?

Conversion factors/unit conversions are straightforward for some and difficult for others. Developing a positive learning environment where students who are struggling are able to voice their concerns and get help without leaving other students bored can be a challenge. In some cases, students may struggle and want to give up. This is a good time to remind them of their goals for a growth mindset.

A student worksheet is provided as part of the resources for the Measuring Sticks Lab. Instructors can choose to use this worksheet in lieu of the science journal format. Make a choice now: do you want to follow the science journal format, or do you want to continue with worksheets? If using the science journal format, then powerpoint slides are all that is needed (no worksheet). As the course goes on, we will often but not always provide student worksheets. In classes with time constraints, worksheets can be faster, but they do not ask your students to engage as deeply with the practices of science.

A pre-class assignment is graded for completion only, not correctness. Administer using the same format throughout your course (through the LMS, turn in paper copies, guided discussion/participation in class, etc.). Consider setting the due date an hour or so before your class begins to give you time to summarize where your students sit with these concepts (this is a form of Just in Time Teaching).

The Lab(s) is/are assessed as a Science Journal, as always. Science/Lab Journals General Instructions/Rubric (Microsoft Word 2007 (.docx) 2.9MB Aug30 24).

Donald G Wiggins. (2017, February 12). Unit conversion. Visionlearning. https://www.visionlearning.com/en/library/Math-in-Science/62/Unit-Conversion/144