Math-Tool Drawer: The Pad Investigation

Sorting the Classroom Pad Kit

A fifth-grade class is organizing the drawer that holds its math tools. A supply kit contains pads that could line the drawer. Some pads have material labels; others have letter labels. The class investigates before sorting the kit. The labeled materials are cork, wool felt, soft closed-cell foam, and synthetic sponge. The kit maker says each lettered pad is one of these four materials.

Step 1: The teacher supplies precut pads with smooth edges. Each pad is a square measuring 5 centimeters on each side and 10 millimeters thick when dry and unloaded. Students look closely without pulling the pads apart. They record tangled fibers on the wool felt and visible holes in the synthetic sponge. They use a balance to measure each dry pad's mass to the nearest gram.

Step 2: Students test how much the dry pads compress, or become thinner under a load. They place one pad on a level desk and put a lightweight, flat plate on it. They center a sealed 500-gram bag of rice on the plate. After 20 seconds, they measure the pad's thickness beside a ruler. They measure the pad itself, not the plate or bag. They use the same plate, bag, and waiting time for each pad.

Step 3: After removing the load, students let each pad rest until it returns to its starting thickness. They place each pad in its own cup of room-temperature water for 60 seconds. They lift it out, let it drip for 30 seconds, and touch its surfaces with a towel without squeezing it. Then they measure its mass again. Water gain is the mass after soaking minus the dry mass.

The class tests two labeled pads of each material and records the same rounded results both times. The table shows the mass records, and the graph shows thickness under the load. Students test the lettered pads using these same steps. These records describe this kit under these conditions; pads from other sources may give different results.