The first section was on thermal energy transfer. Conduction, convection, radiation. A diagram showed how heat moved through solids, liquids, and gases. Leo’s eyes landed on a sidebar: "Mystery Sound? Check for thermal expansion."
A spark lit up in Leo’s brain. Not a ghost. A temperature change. addison wesley science and technology grade student book
Leo stared at the closed copy of his Addison-Wesley Science and Technology Grade 7 student book. On the cover, a shimmering hologram showed a DNA helix unwinding beside a robotic arm assembling a solar panel. Inside, he knew, were chapters on "Interactions in Ecosystems," "Pure Substances and Mixtures," "Form and Function," and "Heat in the Environment." But right now, all that knowledge felt like a locked vault. The first section was on thermal energy transfer
Thermal expansion? He read on. When materials heat up, their particles vibrate faster and take up more space. When they cool down, they contract. This movement, especially in large structures like bridges or old brick walls, could create stress—and sometimes, sounds. Leo’s eyes landed on a sidebar: "Mystery Sound
But his evidence wasn't complete. He needed to show the absence of sound when there was no temperature change. The next afternoon, he waited until the sun had baked the wall to 28°C. He ran a garden hose over it for ten minutes, rapidly cooling it down. The instant the water hit, a loud echoed from the wall—followed by the same mournful hum.
Reluctantly, Leo cracked open the book to Unit D: "Heat in the Environment."
Case closed.
Language: English