Relate observations of diffusion to particle motion.
observed the instructor mass an orange, plate, and napkin. These items we identify as the mass system. The instructor
then cut the orange into slices on the tray and wiped the knife clean with the napkin, and then instructed the students to
immediately notify the class when they smelled the orange from where they were sitting in the room. As they waited,
the class observed that the mass of the orange was decreasing (scale reading). Eventually students sitting closest to
the orange smelled it first. Over the course of a few minutes, the students farther away smelled the orange, too.
Students noticed that the mass of the orange continued to decrease.
All students did a storyboard of how they thought the orange particles diffused (defined
in an earlier classroom discussion) throughout the classroom. Storyboards indicated that the particles are mobile, and
move through the air. Even though the air in the room appeared still, the particles left the orange and traveled throughout
the room. Student ideas indicated they believe that the air particles in the room are in motion even though they cannot
feel them moving, and that this is a result of particle collisions between the air and the orange forcing some of the orange
particles into the air.
and student work allowed students to add a new facet to the particle model: The particle is mobile, and are moved
through collisions with other particles.