Introduction to Metric (Day 1)
Lesson 9 of 16
Objective: SWBAT convert among different-sized standard measurement units within the metric system and use these conversions in solving multi-step, real world problems.
This 6 minute video, from Math Playground, provides a great overview of the Metric System. Very simply put, the chart is started in the middle, on meters, and then moved, and multiplied/divided to fill in the rest of the chart. I like using this before students get their own chart because the students are exposed to the mnemonic device (King Henry Died By Drinking Chocolate Milk, and how useful it is. With guidance, students practice a few sample problems as well.
To start, students explore shades of meaning (words that have slightly different meanings) for convert. Another way to use shades of meaning is to use a staircase of words, and you can even use paint sample "bookmarks" to write one word on each color.
I support my ESL learners by writing convert on the board, having students say it. Then, students define it in their own words. (Now they do have some previous knowledge from the clip that we just watched, so I'm expecting that even my ESL students should be somewhat able to respond back regarding this.)
One of my students responds that to convert means to change from one type of currency (money) to another. I write change from one form to another under convert on the board. I explain that sometimes in math, you have to convert a unit of measure to another unit.
I write: I converted _______ to ________.
Then students talk about the similarities of the definition on the board with their own. In order for students to be successful, they need to know how to multiply and divide by powers of 10. I remind students that dividing a number by 10 shifts its place value right. So, dividing a number such as 3250 by 1000, which is 10 x 10 x 10 or (10 to the 3rd power), shifts the digits right three places. To solve the problem successfully, students need to recognize which unit is larger and which is smaller, so I set them up for this by using fill in the blank lines. Then, they need to decide whether to multiply or divide by 10 and what power of 10 to use.
Throughout the next few lessons I will continually ask, when students need help "starting", whether they expect to get a larger or smaller number as an answer in order to prompt them to realize which section of the chart to move to.
Using the prefixes on the chart is crucial to having students remember the mnemonic device. I point out that the prefixes in this chart--kilo, hecto, deka, deci, centi, and milli. The relationship between each unit is 10 times the next smaller unit, and 1/10 the next larger unit.
Using Guided Practice Notes 1 and Guided Practice Notes 2 documents, we take notes together as a class. These guided notes are intentionally somewhat lengthy notes, and may seem repetitious. I need my students to practice writing the prefixes a few times though with different bases as examples in order to remember the mnemonic device.
In this Think-Pair-Share question, students look for and make use of structure (MP7) in the relationship of metric units to solve a problem. As I work with students I use the question, "How does the size of a gram compare to the size of a kilogram?" to help students who are stuck. This is a great jumping off point because then students know where on the chart to be looking (on the left for the 1,000 increment.
Josh has a 15 kilogram bag of rice. A serving of rice has a mass of 200 grams. He wants to find the number of servings of rice the bag contains. Should Josh convert kilograms to grams or grams to kilograms?
As students work, I facilitate by asking them if they expect a larger or smaller number as the answer. Then, if they need more assistance, I lead them to determine which unit is larger/smaller, and then whether they need to divide or multiply. Example: "How does the size of a gram compare to the size of a kilogram?"
To close out this lesson, we revisit the I Can Statement. Using cold calling to ensure I am treating students equitably, I ask what students have learned today. One student comments, "I can use the King Henry chart with all the metric units." Another says, "If I change to a larger spot, I divide by 10 for each spot I move in the chart."
I paraphrase this response, and restate it using the key words: convert and unit. It's important not to embarrass students for not using the academic vocabulary, but rather by restating it like this students are again exposed to it being used correctly. After enough practice with the words, students will begin to use it as well. I prompt more discussion by asking what if you're converting to a smaller unit. A student answers that, "You multiply by 10 for each unit you move in the chart."