Changing Metric Units

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Objective

SWBAT convert units of measure within one system of measurement.

Big Idea

Students can use a conversion chart to help convert units.

Whole Class Discussion

15 minutes

I let the students know that we are wrapping up our unit on measurement.  We have studied the customary units of weight, length, and capacity.  We have also learned about the metric units of weight, length, and capacity.  Now that we have studied these metric units, we are going to as we did with the customary units.  We will convert units of measure from one unit to another unit (4.MD.A1).

We learned which unit was smaller or larger.  We need that information for our lesson today.  To review, I ask the students, If we go from a unit that is smaller to a unit that is larger, what operation will we use?  Student response:  multiplication.  To give the students an example, I tell them that if we go from liters to milliliters, we are going from larger to smaller.  Therefore, we must multiply.  It will take more than 1 milliliter to equal 1 liter.  Thus, the number is getting larger.  To give the students a visual of this, I have a student hold up 1 liter of water.  I explain to the students that this water represents just 1 liter.  The student then pours the liter of water into 2 containers.  One container holds 600 milliliters of water, and the remaining water equaled 400 milliliters in the second container (Liters to milliliters).  I let the students add 600 + 400 to get 1,000.  Pouring the water from a larger container into smaller containers give the students a visual of what "converting" means.

I go on to remind the students that when you go from a smaller unit to a larger unit, you divide.  If you go from milliliters to liters, you divide because it will take less liters to equal millimeters. This is shown by pouring the water from the two smaller containers back into the 1 liter container.  

I tell the students that we are going to use the same strategies that we used to convert the customary units.  The students learn to make a chart or multiply or divide to find the answer.  

On the Smartboard, the Teaching Tool - Changing Metric Units is displayed with a metric units chart.  The students are at their desks with a sheet of paper so that they can work the problems as I work them on the board.  

I have 4m and I want to convert them to millimeters.  I ask the students to tell me what the chart says about meters and millimeters.  (By asking this, I want the students to get accustomed to using the chart to help them convert within units.)  The chart tells us that 1 meter = 1,000 millimeters.  I have the students write this information on their papers.  I draw a chart on my paper with meters on one side and millimeters on the other side.  Together, the students help me fill in the chart until we get to 4 meters.  

meters

millimeters

1

1,000

2

2,000

3

3,000

4

4,000

I remind the students that whatever the first number is in the chart, that is the number that you are counting by.  The students easily found that 4 m = 4,000 mm.  

To give the students more practice, I have the students write 8 kg = ____ g.  I ask the students to refer to the chart to see what it tells us.  The charts tells us that 1 kilogram equals 1,000 grams.  Again, we make a chart to find the answer.

kilograms

grams

1

1,000

2

2,000

3

3,000

4

4,000

5

5,000

6

6,000

7

7,000

8

8,000

We discuss that because we are going from kilograms to grams, this is going from larger to smaller.  We multiply when going from larger to smaller.  Because we have 8 kilograms, we can multiply by 1,000.  This gives us 8,000 kilograms.

In the next problem, the students learn to compare using greater than, less than, or equal to.  The students write 2,000 mL ____ 3 L on their paper.  I tell the students that we can also draw a chart when comparing units with greater than, less than, or equal to.  I ask, "What two units should be put in our chart?"  Student response:  liters and millileters.  "Which one is bigger?"  Student response: liters.  Together, we make a chart. (I tell the students that I always write the largest unit in the chart first because it starts with 1.  It makes it easier for me to find the answer.)    I explain to the students that we can not compare milliliters to liters.  The units need to be the same.  We have to convert from one unit to the other to see how they actually compare to each other.  I let the students know that I am converting liters to milliliters.  I make it clear to the students that they can convert which ever unit that they want.  

liters

milliliters

1

1,000

2

2,000

3

3,000


I have the students write 3,000 mL underneath 3 liters in their problem.  (By doing this, I want the students to look at the 2,000 mL and compare it to 3,000 mL.)  The students see that 2,000 mL is less than 3 liters.   

To give the students independent practice, I let them try the last problem without me as I walk around to monitor.  Upon completion of this last problem, the students work as pairs on the activity.

 

Skill Building/Explore

20 minutes

For this activity, I let the students work as pairs to match the correct equivalent customary units.  By doing this, it allows the students to hear their classmates thinking on the skill (MP3).  

I give each pair a Changing Metric Units Activity Sheet.  The students must convert from one unit to another by using strategies such as multiplying, dividing or drawing a chart.  The students are required to work together on each item.  As the pairs discuss the problem, they must be precise in their communication within their groups using the appropriate math terminology for this skill (MP6). As you hear in the Video - Converting Metric Units, the students must use reasoning and strategies to find their answers.

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

1.  What does the metric unit of measure chart tell us?  

2.  What strategies can you use to find the equivalent number?

3.  Are you converting from a smaller unit to a larger unit or a larger unit to a smaller unit?

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:

One pair of students had 500 cm = 50 meters.  I asked the students to explain their answer.  From the metric unit chart, the students used 1 m = 100 cm.  They noticed in the chart that they made that they were counting by 10 instead of 100.  I let the students know that they have to be careful and pay attention to what they are doing in solving the problem.  Another mistake that I noticed as I walked around the room, one pair of students wrote the information from the metric chart incorrectly.  For example, the problem is 2,000 mm = ___ m.  The students put 1 mm = 1,000 m.  They wrote the information from the chart wrong.  It should be 1 m = 1,000 mm.  At the end of the activity, as a whole class, we discussed the importance of checking our work to make sure we do not make mistakes.  I let my students know that math practice 6 tells us to attend to precision.  

Closure

15 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 - metric units and Student Work on Metric Units), as well as work that may have incorrect information.  More than one student may have had the same misconception.