In K-2 Morning STEAM, we used recycled materials to build our own marble runs. First, we talked about how marble runs work and the forces (gravity, friction, etc.) that come into play. We also discussed momentum. I gave each student a large sheet of thick posterboard that was donated from a family. Next, I piled up about 100 paper tubes, old foam insulating tubes, and cut foam core pieces (I made them about 3"x2"). Each student was given a roll of masking tape, scissors, and tons of marbles to test it out. For young students (and those that needed a starting point), I drew a zig zag on their large posterboard to give them some guidelines as to where to place their run. Students had a lot of fun and I enjoyed seeing their creativity and problem solving at work. One huge hint I gave students is to test out thier run after adding EACH piece. This saves a lot of time and eliminates most frustration for them later on.