This lab sheet guides grades 4-6 homeschoolers through a structured investigation into how moisture affects fiber strength. Students cut six natural fibers to the same length, suspend each one bridge-style between two chairs, and add coins or washers one at a time until the fiber snaps, recording weight held across three dry trials and three wet trials per fiber. The natural fibers are strongest when wet question drives the whole experiment, and the data table has a built-in percent-of-dry-strength column that introduces your student to proportional reasoning alongside the science.

This sheet fits naturally into a materials science unit study or a broader textiles and natural resources unit. It works as a standalone two-session lab: one session for dry testing, thirty minutes of soaking, then wet testing in the same sitting. By the time your homeschooler fills in the conclusion section and answers the three analyze prompts, they have demonstrated controlled variable design, repeated trials, and data-based reasoning.