We built gnome bridges to test materials to find the ones best suited for building a “bridge.” This activity also met a few of the engineering standards that we have.
Yesterday, after an investigation where we classified materials based on their observable properties, the students generated the list of materials that they thought would work best for building their model bridge. This came after we talked about other materials and their purposes. For example, why are houses no longer built with the materials we read about during our long-ago unit? Why have they started to use different materials? How are materials from construction used in other ways? Do materials serve multiple purposes?
Students designed a bridge first, thinking about different materials and their properties. Some students thought a popsicle stick would be a strong enough support, but soon discovered that they needed something with a wider base, like a cup. Some thought string would work to hold up the bridge, but realized the string itself did not keep the bridge stable enough -- they needed to thread the string through something, like a straw. Students stopped mid-way through the building make sure they had all of the essential components of a bridge, including a way to get on to the bridge. Students then had to decide on materials that were flexible enough to attach to the bridge and the ground, yet also stable enough to further support the bridge.
After building the bridges, we debriefed together as class. This included looking at classmates' bridges and talking with them. It was so cool to see the students going around, pointing out things they had not thought of for their own bridge. Students talked about how their original designs had to change and why. We will be completing an additional experiment that tests different materials to see which are more absorbent, and we will be collecting and analyzing actual data for this investigation. Also, this bridge-building experiment comes back around (but in a different context) at a later time in the year, and we revisit and revise some of the knowledge gained from today.