Teacher quietly sprays perfume or Pine-Sol, or opens a container of ammonia, or lights a match and burns paper. As the particles move from the area of higher concentration to areas of lesser concentration, the students should be able to sense the substance and raise their hand. Before the particles have reached the front of the room, the teacher asks students to look around, observe the room and those hands that are raised. Shortly thereafter all students should be able to smell the selected substance. Using a pipette, drop one or two drops of extract deep into a balloon.
Students blow up and tie balloons and set on desks for constant observation.
Do this at the beginning of a class period and move on to other activities while students are silently observ- ing. Within 5-10 min. Discussion and hypotheses follow. It smells like homemade cookies. Diffusion characteristics are noted and conclusions can be made.