Eighth Graders Separate Mystery Substances During ‘Sludge’ Test

Two students doing a science experiment
Bronxville, NY

Equipped with a variety of laboratory equipment, Bronxville Middle School eighth graders conducted science experiments that challenged them to separate different substances during the annual “sludge” test, a tradition at the Bronxville School for the last 50 years. 

Under the leadership of science teachers Jean Windels and Jennifer Zopp, the test served as an assessment of everything the students have learned in the first semester and provided them with free reign to come up with the procedures to accomplish the task. At the beginning of the weeklong experiment, the eighth graders received a sample of “sludge,” which contained a mixture of liquid and solid components, and were tasked with separating the substances into their unique component parts. 

“Some of the techniques the students used were fractional distillation, straining, dissolving and filtering solids, and evaporation,” Windels said. “The students had to determine the physical properties of each of the substances in order to prove to themselves and their teacher that they have been successful.” 

Throughout the week, the students completed a daily journal to record their thoughts and ideas about the project and come up with a plan for the following day. In their report, they included the procedures for accomplishing their task, as well as graphs and data tables. They also made claims about the contents of their “sludge” and supported it with evidence and reasoning.

Eighth grader Greta Warren, who used a coffee filter, burner and evaporating dishes to separate the substances, said she found the laboratory experiment rewarding. She enjoyed collaborating with her peers, as well as the creative liberty over applying her knowledge to accomplish the task.  

At the end of the experiment, the students reflected on the process, as well as their challenges and successes. The project fostered the students’ critical thinking skills and allowed them to engage in self-directed learning.