Measuring Volume of Rectangular Objects
Lesson 8 of 13
Objective: SWBAT understand that volume is a measurement of 3 dimensional space and will know how to measure it using a ruler and a formula (length x width x height).
In my classroom, I have a set of math manipulatives that I use for teaching volume of rectangular objects. They are similar to square legos and can be used to make larger blocks using the individual pieces.
For this activity, I give each child 6 small building cubes. In 2 minutes, I give them the following prompt:
Construct a larger rectangular block using your 6 small building cubes. Put them in any arrangement you wish.
At the end of 2 minutes, I ask them to put their blocks down on their tables. Now I ask the students to write down the following information in their student notes sheet, giving them 1-2 minutes to do so:
How many cubes wide?
How many cubes high?
How many cubes long?
I show the following visual on the board to help them with length, width and height in case they need a visual reminder.
For this next part of the lesson, I want the kids to make connections between metric measurements and length, width and height to prepare them for the final step in measuring volume of regular solids.
In their notes, I ask them to think about and answer the following questions:
If each cube is 1cm wide and 1cm long and 1cm high…
How many cm WIDE is your block?
How many cm LONG is your block?
How many cm HIGH is your block?
After about 4 minutes, I ask students to share their responses. I'll ask them to explain how they know. For example, "my block is 2cm high." I'll say, "how did you figure that out?" Hopefully, they will say something along the lines of: "my block is 2 cubes high and since each cube is 1cm, I added 1+1 or I multiplied 2x1."
As a class, we complete the EXPLAIN section of the notes together. I put the document on the SMARTBoard and the kids complete it individually.
The formula for finding the volume of a rectangular object is…
To find the volume, you need to measure LENGTH, WIDTH and HEIGHT.
To measure these, you can use a…
Some students need a visual of where to place the ruler to find the necessary measurements. I stand in front of the class and hold a block and a ruler, reminding them to place the ruler on the far edge and the 0 mark. It helps to have them keep their block in the same position and move the ruler to the various sides.
Using the formula LxWxH and a metric ruler, students calculate the volume of 5 different blocks (I have wooden blocks of various sizes that I place on the tables). Students write their measurements in their notes sheet. I offer calculators at this point because they may be multiplying decimals and to prevent the struggle, the calculator is available.
This video is an example of a student working through the process of calculating the length, width and height. I am reminding him of our process of moving the ruler and not the object in order to measure three different sides. This is the most confusing part for the students.
After the students have had some interaction with calculating the volume of regular objects, I now ask them to think about what it is they are actually measuring. What is volume?
I show them a picture of a 2D block and ask them to find the volume. After about 30 seconds, someone will say, "But there's no length!"
I say "EXACTLY! So can we measure volume? No."
Then I show them the same 2D block but now in 3D. I ask them to tell me what's different. (It has a 3rd dimension. We have everything we need to measure volume.)
Then I say, so what's the difference between 2D and 3D? (3D takes up space)
So, volume is a measurement of the space a 3D object takes up! I ask them to write their definition of volume in their notes. This allow them to construct their own idea of it using examples from the lesson.