Sort it Out Engineering Lab

Earlier this month, schools around the U.S. celebrated National Lab Day with hands-on science learning experiences. Students in my district completed the Sort it Out experiment provided by Try Engineering.

Before beginning the lab, students can be briefed on the role of engineers through the Discover Engineering website introduction and What's Engineering page. For this experiment, students begin by collecting household materials including cardboard, wire hangers, and disposable plates and cups. Then students work in teams to plan out the design for a machine that will sort coins or buttons by size.
In my classes, this phase took most of a 45-minute class period. On the second day, students request the materials they need and begin construction of their machines.
Construction in my classes took an hour or more. After students have built their machines, it's time for testing.
As you can see, the approaches were many and varied. Some of the machines worked well, while others had low accuracy rates. This creates a great opportunity to discuss the scientific method and the fact that incorrect hypotheses are just a chance to try again.

Once the machines have all been tested, students can reflect and write reports of their success rates and possible ways to improve the machines.

Since the materials for this experiment are all reused junk, this lab would tie in well with a unit on environmental science and conservation.