Journal Thread #1 / Prompt 4 - One Little Problem
Step into the shoes of a lead metrologist and plan how you would persuade your country's leaders to make the switch to using universal constants as standards.
Teacher Tips!
Many activities have a teacher view and a student view, and teachers can switch between those views by clicking the blue button in the upper-right. Students will not see this option - only teacher accounts see both views. The teacher view will start with overview text, if available, to frame the activity and get you started. This view will also have teacher tips and suggested answers to student questions spread throughout the activity. The teacher text interleaved with student-facing text will be in italics and should appear as a different color on your screen. Teacher tips are designed to help you deliver a learning experience that is best suited for your classroom.
Printing Reminder
Whichever view you see on your screen is what will print. You can print this activity without teacher tips by selecting the student view, or print with teacher tips by switching to teacher view. Simply use the standard print function available for your web browser. No extra steps are required.
Title of Activity: Journal Thread #1 / Prompt 4 - One Little Problem
Brief Description: Students prepare a short argument for why it is important to redefine the kilogram using constants.
Target Grade Level: Grades 8-12
Discipline or Course: Physical Science
Estimated Time Required: 20 minutes
Individual / Partner / Group Work: Individual
Key Vocabulary:
- Constant
- Standard
- Accuracy
Teacher Prep:
There are two prompts urging students to justify the effort to redefine the kilogram. The first question asks how the metal artifact might change. Students might first imagine it getting smaller through micro-abrasion (touch or even air.) The cylinder might also increase in mass, as chemicals or particulates in the air adhere or bond to its surface. Students should discuss both possibilities.
The second question in the prompt asks “why.” It could be answered by citing either scientific or economic (engineering) problems that could be answered with more accurate measurements. A complete answer would include both current issues (like nano-processes) and future research.
Possible Rubric
| Area | Novice | Average | Advanced |
| Constructing Explanations | No reasonable hypotheses for how the cylinder might change. | Hypothesis for how the cylinder might gain mass or lose mass, but not both. | Hypotheses for how the cylinder might increase or decrease mass. |
| Communicating Information | No discussion of communication for precision | Mention of communication for precision without specific guidelines | Specific guidelines for communication to improve precision are included. |
| Identification of arguments based on evidence | No mention of problems that imprecision in measurement might cause or questions that a more accurate standard might answer | Mention of problems that imprecision in measurement might cause or questions that a more accurate standard might answer but not both. | Mention of problems that imprecision in measurement might cause and questions that a more accurate standard might answer |
STUDENT CONTENT BELOW
Guarded and locked with 3 different keys, hermetically sealed in a glass bell jar, “Le Grande Kilogram” seems perfectly protected. Yet that cesium-iridium cylinder can change over time.
The process of redefining the kilogram was long and complex. It was also controversial. Metrologists from all over the world debated whether it should be done and how.
Imagine you are justifying your country’s expenses for the work of its metrologists redefining the kilogram in terms of a universal constant. The budget-masters ask: “How could it change?” and “Why would such a tiny difference matter?”
Prepare a short argument for your congressional budget committee justifying your participation in a process to redefine the weight of the world.
.
