Units of Mass

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SWBAT determine the appropriate unit of mass with which to measure an item.

Big Idea

Students learn that mass is weighed in grams and kilograms.

Whole Class Discussion

15 minutes

 In today's lesson, the students learn to choose the correct unit of mass to measure an item (4.MD.A1).  The students have previously learned the different customary units of length, capacity, and weight.  Today, they learn about the metric system and the units of mass.

To begin the lesson, I bring the students to the carpet to watch a Brain Pop video at the following site.

After the video finishes, I discuss with the students what we saw.  I remind them that mass is the amount of matter that something has in it.  To review from the video, I ask the students,  Which is larger, grams or kilograms?  Student response:  kilograms.  I ask the students if we should weigh light things or heavy things in grams.  Student response:  light.  I remind the students that the video shared with us that we should weigh heavier things, like people, in kilograms.  I tell the students that 1 kilogram is equal to 1,000 grams.  This means that a kilogram is 1,000 times larger than a gram. 

I tell the students that in their activity, I do not want them to tell me how many grams or kilograms something weighs, rather, I want them to identify the most appropriate unit of measure for an item.  Itt is important to know which unit is larger or smaller because in the near future we will convert metric units just as we did with the customary units.


Skill Building/Exploration

20 minutes

For this activity, I let the students work as pairs to explore and determine the correct metric unit of mass to use to measure certain items.  By doing this, it allows the students to hear their classmates thinking on the skill.  

I give each pair a Units of Mass activity sheet.  The students must determine the correct metric unit of mass to use to measure items found in the chart. The students are required to work together on each item.  The students must also list items not identified on the chart and tell if it would be measured in grams or kilograms. I let the students know that during the closing of the lesson, we will actually measure the mass of an item.

 As they work, I monitor and assess their progression of understanding through questioning. 

1.  Is this item light or heavy? 

2.  What is the most reasonable unit of mass to use?  How do you know?

3.  Can you use a different unit of mass?  Explain.

As I walk around the classroom, I am questioning the students and looking for common misconceptions among the students.  Any misconceptions are addressed at this point, as well as whole class at the end of the activity.

My Findings:

I am very proud of the students.  I have to say that in each unit as we have learned to determine the appropriate unit of measure, the students have gained a great understanding of which unit is the larger or smaller unit.  (One challenge has been with converting the customary units.  In the next few days we will convert metric units.  I expect this to improve as well, as this will be the second time working on converting.)


10 minutes

To close the lesson, I bring the students back together as a whole class.  I feel that it is very important to let the students share their answers as a whole class.  This gives those students who still do not understand another opportunity to learn it.  

I feel that by closing each of my lessons by having students share their work is very important to the success of the lesson.  Students need to see good work samples (Student Work - Units of Mass), as well as work that may have incorrect information.  More than one student may have had the same misconception. During the closing of the lesson, all misconceptions that were spotted during the group activity will be addressed whole class.  

During the closing of the lesson, I wanted the students to actually see how to measure the mass of an object with a balance scale.  Because we knew that a paper clip was 1 gram, we used it to determine the mass of an eraser.  A student volunteer put the eraser in the cup on one side of the balance scale.  Another student put the paper clips in the other side, one by one, until the scale was balanced.  The students all had the opportunity to come around and see how the scale works to show that both sides are balanced.  This was a great opportunity for the students to get the conceptual understanding outlined in the standard.  The eraser and paper clips were passed around the room so that the students could hold them and feel the difference in the heaviness of the eraser than the paper clips.