Investigating Customary Units of Capacity

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SWBAT identify the relative sizes of an ounce, a cup, a pint, a quart, & a gallon and find the number of units in a given container.

Big Idea

Understanding the size of measurement units is a foundational skill needed to solve word problems involving measurements.

Opening Activity

15 minutes

Today's Number Talk

For a detailed description of the Number Talk procedure, please refer to the Number Talk Explanation

Task 1: 33 x 2

For today's Number Talk, I asked team leaders to pass out the Number Line Model to help students show their thinking later on. For the first task, students used Multiple Strategies to solve 33 x 2. Here, a student Decomposed 33 into (30 + 3) x 2. Another student tried Decomposing 33 two times to solve 33x2

Task 2: 4 x 66

When we moved on to 4 x 66, students eagerly shared the following strategies. One student showed how to Decompose 66 and 4 to solve 66 x 4. One of my favorite strategies shared was when a student showed how to Use a Friendly Number to solve 4 x 66! 


Teacher Demonstration

20 minutes

To begin today's lesson, I introduced students to the goal: I know the relative sizes of an ounce, a cup, a pint, a quart, and a gallon and I can find the number of units in a given container. I explained: Over the past five math lessons, we have been focusing on capacity. What is capacity again? Students responded with the Meaning of Capacity: "Capacity! The amount of units a container can hold!" I continued: Today, we will be continuing our study of capacity, only we will now be using US Customary Units to measure the capacity instead of Metric Units. I showed students a poster that categorized the Metric & Customary Systems

Prior to this lesson, I printed Math Stations posters and set up five stations in the classroom for each of my five groups to rotate between. I borrowed materials from two other classrooms to make sure my students were provided with the tools necessary to complete each investigation. Here's a list of the materials at each station:

1. Quarts Station, Materials: Gallon Balance (see picture below)

2. Pints Station, Materials: Gallon Balance

3. Cups Station, Materials: one measuring cup, Gallon Measurement Set (see picture below), plastic tub to catch drips, plastic jug to collect water

4. Fluid Ounces Station, Materials: Gallon Measurement Set, a plastic container with an ounce scale, plastic tub to catch drips, plastic jug to collect water

5. Drops of Water Station, Materials: a plastic container with an ounce scale, eye-dropper, plastic tub to catch drips, plastic cups for gathering water 

I explained to the class: Today, you'll be conducting your own investigations at stations around the room! To help you understand the size of a quart, you'll be visiting the Quart Station. I went over the questions that students would be investigating at each station without telling students which tools to use. I wanted to give students the opportunity to use appropriate tools strategically (Math Practice 5). 



Student Practice

60 minutes


Prior to the lesson, I stapled three half sheets of notebook paper together to create a small Investigation Booklet for each student. I didn't want students to get their math journals wet. At the same time, I wanted to have high-expectations for students by holding them accountable for collecting and recording answers to the questions at each station.

I handed out an investigation booklet to each student and asked each group to start off at one of the Capacity Stations. We then rotated about every 10 minutes. Prior to CCSS, I would have explicitly taught students the conversions between customary capacity units (such as 4 quarts = 1 gallon). Today, I couldn't wait to watch students make these observations on their own! 

As always, during student practice time, I float the room and look for opportunities to support students and to question student thinking in order to help students gain a deeper level of understanding. Below are some of the wonderful conversations I was able to have with students during this time!

Here, students substituted two 1/2 gallons to make an extra gallon and utilized two pints to make a quart. This way, they were able to find How Many Quarts are in 2 Gallons?. Similarly, this group found How many Pints are in 2 Gallons? by substituting 1 quart to represent two pints. Many times, I proudly found students applying the new knowledge that they had just acquired at the previous station to the station they were currently at! 

Also, to enforce the relationship between a balance scale and an equation, I guided students to begin thinking about the fulcrum of the scale as a equal symbol: Relating a Balance Scale to an Equation.

I loved watching these students try to figure out How many Cups are in 1 Gallon? by pouring one gallon at a time in a half gallon and then doubling the total cups it takes to fill a 1/2 gallon. Also, by providing students with a measuring tool that measured both milliliters and ounces, at times, students struggled with Determining the Correct Scale. This was another great learning opportunity!

Here, I ask guiding questions to help a group of students with Differentiating Between Ounces and Fluid Ounces. This is important as we have been using ounces to measure both weight and capacity. I wanted to clear up any confusion!

Another one of my favorite moments was when these students were measuring How many Ounces are in a Cup?. After pouring a cup into the plastic container marked with fluid ounces the students responded, "There are 7 1/2 ounces!" I asked them to look again and they realized that the 7 1/2 mark was really the 8 ounce mark! 

Finally, many groups went on to Discovering Fractions of a Gallon. This group began comparing the number of cups, pints, and quarts equivalent to fractions of a gallon. Again, this was a great reminder that fractions easily applied to most measurement models!  



5 minutes

To bring closure to the lesson, I asked students to clean up the stations and come back to their desks. I then asked students to Turn & Talk: What did you learn about the size of an ounce, cup, quart, or gallon today? Student responses varied:

"I learned that there are 16 cups in a gallon."

"I learned that two pints equal one quart."

 "I learned that there are 8 ounces in one cup."