Sticky Bridges

I'll just blog instead of grading work, because I don't feel like grading work.

I began the bridge-building unit with my students this week. I like the idea of introducing applied science in a physical science class, but it is a little disjointed from the rest of the curriculum. If I were teaching this class again, I would find a way to tie it into previous units on force and energy. Instead, I started from scratch with an introduction of: this marks the end of the class segment on theoretical science, and begins a taste of applied science.

I taught them about a few different types of bridges, showed them some example with pictures and videos, and discussed with them a few things about how they work (e.g. arches distribute weight laterally). I feel comfortable with this because bridge construction is one of the first things I remember learning from my dad. He knows a whole lot about architecture, and would explain design details of various major landmarks we'd pass on long car trips. I may have learned how a suspension bridge works before I learned how to read.

Then came the lab activity day. Students were given unlimited dried fettuccine and mini-marshmallows (Stop and Shop brand) and asked to build a free-standing bridge that could span a gap between tables. Extra credit if the bridge could support the weight of a textbook. The kids were very intimidated from the start, but after a bit of playing around, they discovered the strength of triangles and pyramids as support structures with rigid materials. I also emphasized that applied science is just another way to get involved in the field of science, but with a much better salary. It was beautiful watching the process of learning and discovery. That's what makes me a science teacher. And, after the first class built their bridges, I had a better idea of how to instruct clean-up. The second time around did not leave my classroom a sticky mess. I still have one class left for the activity, but all in all, not a bad way to learn for $20 of materials for 70 kids.

I'm even more excited about a lab I have planned for my 7th graders. We just finished the introductory unit to ecology, including a fantastic discussion this week about natural selection. The students even proved to me how social behavior evolved in humans. The lab tomorrow illustrates natural selection with 4 types of dried beans. Students are given 1 minute to pick up as many beans of the table as they can (as the predator), and then count how many of each type remain. The remaining beans "reproduce", and then the process is repeated. Students will be able to see that they are selecting against beans that are big and easy to pick up, while the smaller slipperier beans survive to reproduce. I'm so excited. I love natural selection and I think my kids are starting to as well. I guess my excitement is contagious.

Today is a half day, so I'm done teaching already at lunchtime. Not a bad way to end a Thursday (I still have a few hours of professional development, though).