Units of Weight

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SWBAT determine the appropriate unit of weight to use in order to measure items.

Big Idea

The students will record the appropriate measurement units in a two-column table.

Whole Class Discussion

15 minutes

To review, we discuss customary units.  What country uses customary units?  Student response:  United States.  So far we have learned about customary units of length.  Someone raise your hands and tell me the customary units of length.  Student response:  yard, foot, inch, and mile.  Those are the units of length to measure how long something is in length.  Yesterday, we talked about customary units of capacity.  That means how much a container can hold.  What are some customary units of capacity?  Student response:  gallons, pints, quarts, and cups.  

I let the students know that in today's lesson, we will talk about customary units of weight.  When you are taking a test or measuring something, you have to know the correct customary units to use.  If you are measuring length, you would not say that "this is one pint" because pint does not go with length.  Pint is a unit of measure for capacity.  

In today's lesson, I share information about customary units of weight using the following site.

I find that using different instructional strategies keep the students interested in the lesson.  

On the screen, the units of weight are displayed:  ounces, pounds, and tons. Which unit is the smallest?  Student response:  ounce.  In the video, what did they say weighed about an ounce? Student response:  a slice of bread.  I tell the students to think back to when they have held a slice of bread.  This is familiar to everyone.  You know about how heavy the bread feels in your hand.  That is about 1 ounce.  I go on to remind them that in the video, it told us that a loaf of bread would be weighed in pounds because you have several pieces of bread together.  The last unit of measure is tons.  How many pounds does it take to make a ton?  Student response:  2,000 pounds.  I told the students to think about a car because a car if very heavy.  Can anyone think of something else that can be weighed in tons?  Student response:  truck, rocket, and elephant.  It is very important to measure things in the right units.  For example, if we were going to measure a car, we wouldn't want to measure it in pounds because it is too heavy.  But, as they state in the video, if we take the car pieces apart, such as the door or tire, we can then weigh those individual items in pounds.  Collectively, the car would be weighed in tons.

I let the students know that they will work in pairs to practice the skill further.

Skill Building/Exploration

20 minutes

I give the students practice on this skill by letting them work together.  I find that collaborative learning is vital to the success of students.  Students learn from each other by justifying their answers and critiquing the reasoning of others.

For this activity, I give each pair a Customary Units of Weight Activity Sheet.  I let the students work as pairs to generate a list of items and determine the correct customary unit of weight to use to measure these items.  By doing this, it allows the students to hear their classmates thinking on the skill.  The students are required to work together by agreeing upon the unit of weight (MP3).  As you hear in the Video - Unit of Weight, the students must use reasoning to find their answers.

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

1. What unit of weight should you use?  Why?  

2.  Is this item heavy or light in weight?  Can a person pick up the item easily?

3.  If you used a different unit of weight, would the number be larger or smaller?  How do you know?

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.

Any groups that finish the assignment early, can go to the computer to practice the skill at the following site until we are ready for the whole group sharing: http://www.sheppardsoftware.com/mathgames/measurement/BestMeasure2.htm




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 (Unit of Weight, 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.

My Observations and Student responses:

The students did a great job on identifying the appropriate unit of weight to use to measure certain items.  In our closure, we discussed what unit of weight should be used to weigh a desk.   The students said pounds.  I asked, "Can we weigh a desk in ounces?"  Some students were confused about this because they knew that it should be weighed in pounds.  I explained to these students that, yes, a desk can be weighed in ounces but the number will be large.  

These are some of the answers the students gave as we discussed as a whole class:

filing cabinet- pounds

book - pounds (we clarified that this depends on the size of the book)

truck - tons

basketball - pounds 

Smart board - tons (This pair of students thought that a Smart board should be weighed in tons.  I explained that when the people came out to install the Smart board, they had to pick the Smart board up and hang it on the wall.  Then I asked, "How should we weigh a Smart board?"  They realized that it should be pounds.

brick - pounds

dog - pounds

As some of the students shared their answers, I heard them say 1 pound.  For example, with the dog, the student said 1 pound.  I clarified that we are not saying that these things would be 1 ounce, 1 pound, or 1 ton.  We are saying that when we weigh these things, their numbers will be given in ounces, pounds, or tons.