Measuring Length

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Objective

SWBAT measure length of various objects using a metric ruler and a meter stick.

Big Idea

This is the second lesson in the metric lessons. This gives students a chance to learn and practice using the tools used for measuring in science class.

Engage

5 minutes

For the first part of this lesson, students practice making observations about metric rulers.  Students respond to the following prompts in their Google Drive folder (we are a paperless classroom). The following prompts are placed on the SMARTBoard in order to guide them through their observations.

Sketch the ruler. Include numbers and letters found on the ruler.

How many numbers are there? What are they?

How many cm are there?

How many mm are there?

How many mm inside of one cm?

Describe a situation when you might use a ruler.

Note: I have the rulers placed on the tables prior to the students entering.  I like to give each child a ruler so they can hold it, see it, use it for themselves. Although this lesson seems rather elementary, it is important to assess the prior knowledge of the students in terms of their measuring skills.  I have found that students often do not remember how to use a ruler to measure length, they make common mistakes (use the inches side, don't align the edge with the 0, don't remember how to measure in mm). This activity gives me a chance to see what they already know and then I can adjust the lessons from there. Looking at Student Work Sample A, I can see the student knows the basics of the ruler, but doesn't necessarily understand when to use a ruler.  "You can also use a ruler to measure things that are small."  Student Work Sample B, again, shows that the student understands it's used for measuring, but not necessarily what specifically it measures. To understand the reason for being so explicit, watch the video below. 

Explore

5 minutes

Now that the students have handled a ruler, it's time to show them how to use it. For the second part of the lesson, I give each table a wooden block.  They all have the same block and I have one in my hand, as well. I ask them to measure the length of the block.  I don't tell then what length is or how to use the ruler. I want to see if they either know how or can figure it out. 

After 3 minutes, I poll the tables to see how confident they are in their measurement. One or two tables share out their measurement. I write them on the board to compare responses.  I also ask the same groups to explain to me how they came to that measurement, walking me through it step-by-step.

Explain

10 minutes

At this point, most students have a decent understanding of where to place the ruler on the object in order to measure it.  What they may not understand is how to measure something using decimals (10.5cm or 5.2 cm).  They also sometimes need clarification in placing the 0 at one end of the object and begin measuring from the 0. 

In order to share this information with them, I do a quick 5 minutes demo with my block and ruler, walking them through the steps.  I ask students along the way...what should I do next? After this, not what? I write down the steps on the board as I go and ask that they do the same in their digital notebooks (or regular notebooks).

1. Place the object flat on the table.

2. Place the ruler on the longest side with the 0 at the edge.

3. Wherever the object stops on the ruler is where the measurement is recorded.

4. Write down the number to the LEFT of the end of the object.

5. Count the number of mm after the number.

6. Write your measurement as a decimal.

7. Include units, CM.

Elaborate

10 minutes

Now I give the students a chance to practice their measuring skills. I place 3-5 objects in a basket on their table (nails, blocks, books, calculators, erasers, etc.).  I give them a chart to complete for their measurements.  They spend about 10 minutes measuring and recording their answers. After about 8 minutes I have the students share their responses with their table mates.  Any discrepancies between the measurements should be resolved and checked.

Note: I am walking around from student to student redirecting anyone I see not using the ruler properly. I may ask them a guiding question, "what do you do after placing the object on the table?"

Evaluate

5 minutes

For the last part of the lesson, I want the students to show me and their classmates exactly how they measure length.  I have a few pictures on the SMARTBoard of various objects.  With the interactive ruler, students will measure and write their measurement to the nearest mm. During this process, I make sure to have the kids verbally explain what they are doing aloud to the entire class. 


Then, I ask students to explain in their own words what length is. They can write this down in their notebooks. If there is time I ask the students to share their responses aloud.