Students attempt to create “bricks” (rectangular prisms) with the dimensions 2cm x 2cm x 5cm out of Silly Putty.
Students are encouraged to measure frequently with a ruler, change the brick to have more or less material, cut/smash with the ruler edge.
When most are complete (not necessary for all to finish), ask students to calculate the volume of their bricks with a ruler (20 cubic cm).
Elicit student-constructed definition of volume… encourage “how much space a shape takes up” or “the number of cubic units”
Discuss or write down any observations or challenges that students recall from the experience.
Honor the fact that the students know the formula for volume (l x w x h), but let the in on the fact there is another very different way to determine volume. It involves water, a paper clip, and a graduated cylinder. Let them play with apparatus and their brick to come up with a few ideas.
Seize upon the thinking of students on the right track. Eventually the procedure of displacement is demonstrated by teacher or student.
Note water level prior to submerging brick.
Note water level while brick is submerged.
Determine the difference (how much water was displaced).
1 mL = 1 cc
Discuss. Come up with student created definitions of mL and cc.
Students compare the volume as determined by displacement to the volume calculated from the dimensions’ measurements. It will probably not match. This is because neither is super precise. Ask students:
Think about which method you think might be more precise.
Displacement is more precise, because the shape of a handmade brick won’t be very regular.
Give students time to adjust the size of their bricks if they feel that they can get closer to an accurate representation of 20 cc.