Clock Tower Cover Clues

Inside the Winter Clock Tower

Snow covers the roofs around the town clock tower. Inside, repair workers are checking the north clock and the south clock. Each clock has a removable cover behind its face. The labels on the cover materials are missing. Before planning repairs, the workers want to identify the materials. They also have two unlabeled pieces from a pouch of repair supplies.

Amina, an adult repair worker, prepares a reference collection of four known materials: steel, aluminum, acrylic plastic, and rubber. She cuts one square from each supply sheet before students arrive. Every reference square is 3 centimeters long, 3 centimeters wide, and 3 millimeters thick. Pieces taken from the old covers and repair supplies have these same dimensions.

Students measure mass with a balance that displays whole grams. They check that it reads zero before each measurement. The graph shows their reference measurements. These readings describe the pieces tested, not every object made from those materials.

Next, students bring the same magnet close to each square. They use an enclosed, battery-powered tester to check whether electric current passes through a square. Its indicator lights when current passes. Amina checks the tester before use. The squares are clean and dry. No wall outlets are used.

For flexibility, Amina applies the same gentle push to each square in the same holder. Students record whether it bends and springs back. They do not use a stronger push if a square stays straight. They repeat each test to check their observations.

Reference results: Steel is attracted to the magnet, lights the tester, and does not bend under the gentle push. Aluminum is not attracted, lights the tester, and does not bend. Acrylic is not attracted, does not light the tester, and does not bend. Rubber is not attracted, does not light the tester, and bends and springs back.