Tide-Pool Survey Kit: Predict the Mystery Materials

Preparing a Tide-Pool Counting Frame

At Pebble Cove, volunteers use square counting frames to mark small areas while observing tide pools. Before assembling a new frame, a youth science team examines a supplier's sample kit at a dry beach worktable. The kit contains labeled reference strips and mystery strips. Each mystery strip is one of five materials: pressed cork, closed-cell foam, dense rubber, pine wood, or aluminum. The team will identify the materials and predict how the mystery strips will behave in repeated tests.

An adult supplies smooth, uncoated strips with rounded edges. Each strip is 12 centimeters long, 2 centimeters wide, and half a centimeter thick. The team first dries each strip and measures its mass on the same balance to the nearest gram. Equal dimensions matter: a large piece and a small piece of the same material can have different masses. The recorded masses describe these particular strips, not pieces of every possible size.

Next, the team tests bending. The same student gently tries to curve each strip halfway around the same smooth cup. The student stops if a strip resists; no one forces or breaks a strip. The team records either 'curves around cup' or 'stays nearly straight.' For the floating test, students use a deep container of room-temperature tap water. They gently push each strip just below the surface, release it, and watch for 30 seconds. They record whether it returns to the surface or rests on the bottom.

The team repeats the tests with a second set of labeled strips and gets the same results. These records become the reference for identifying the mystery strips. Unless a question says otherwise, mystery strips have the same dimensions and are tested in the same way. The team tests materials at the worktable, not in a tide pool. No animals or plants are collected. Salt water is nearby, but the reference floating tests use fresh tap water.