Can you get your head around this?
"Start with a millimeter, which is a line this long: -. Now imagine that line divided into a thousand equal widths. Each of those widths is a micron. This is the scale of microorganisms. A typical paramecium, for instance, is about two microns wide, 0.002 millimeters, which is really very small. If you wanted to see with your naked eye a paramecium swimming in a drop of water, you would have to enlarge the drop until it was some forty feet across. However, if you wanted to see atoms in the same drop, you would have to make the drop fifteen miles across...you can get some idea of the proportions if you bear in mind that one atom is to the width of a millimeter line as the thickness of a sheet of paper is to the height of the Empire State Building"
The above is part of a chapter entitled, "The Mighty Atom", from Bill Bryson's A Short History of Nearly Everything. We read this as a class this week and tried to get our heads around first the size of the atom and then the even smaller size of everything in it. The students came to understand and identify with what James Trefil (an American Physicist) said, "Thus an atom, if you could see it, would look more like a very fuzzy tennis ball than a hard-edged metallic sphere (but not much like either, or indeed, like anything you've ever seen; we are, after all, dealing here with a world very different from the one we see around us)." They were perhaps comforted by the knowledge that it takes some scientists a lifetime to comprehend the life of an atom, and some probably never get there. Trefil also said that for the first time, as scientists pondered atoms they had encountered "an area of the universe that our brains just aren't wired to understand." Richard Feynman, also a famous physicist, made a similar statement when he said, "things on a small scale behave nothing like things on a large scale." I read this and immediately compared it to learning a new language, some of this is so foreign to how we think that it requires a totally new perspective, and a whole lot of time.
That said, we have to start somewhere. After reading the chapter, students were asked to develop a list of atomic models over time. Beginning with Dalton's model they identified, Thomson's, Rutherford's, Bohr's and finally the Cloud model. They learned about protons, neutrons, their charges and their life in the nucleus. Then they were introduced to electrons. Grasping what the world of science understood at a given point in time is interesting, but how does that really help us learn about the atom? I would argue that figuring out WHY the theories changed, and what has lead us to our understanding today (the cloud model) is of great importance and supports students in understanding not only the atom, but the process with which we "figure things out" and how science helps us to do so.
The students are currently in research mode, exploring the above. Yesterday they came in to class still disappointed to have not had a full day off to play in the snow. I opted to let them use the snow to create a simple model of the atom (based only on their current understanding). If you listen to the students and their understanding it is evident that there is a bias towards a simplistic view of the atom. Making models of something too small to see, or perhaps even comprehend is difficult. Reiterating Trefil's quote above, "we are, after all, dealing here with a world very different from the one we see around us". This is a first step in trying to get our heads around the atom.
Working to construct an atom
The match stick ends (in green) represent the electrons. The snowball represents the nucleus.
Starting to "make" an atom representation on the brick wall (this is the "fuzzy tennis ball" that Trefil describes in his chapter, the outside edge of an atom).
constructing an atom
explaining the addition of matchsticks to represent electrons
explaining their model
The atom up close, a fuzzy edge, the nucleus and the matches indicating electrons.
I expect by the end of this investigation the students will all have a solid understanding of the atom, of its structure and eventually how atoms make up elements. It will be interesting to note, over time, how their interpretation and understanding of the atom changes, I'll keep you posted.
We hope you will continue to follow the scientific adventures of the 7th grade and the other middle school classes on Kara's blog.