Air under pressure and spread over a large area can support a great deal of weight. Students can discover this property with a simple project that creates a magic trick for the enjoyment of their classmates. Place a strong plastic shopping bag on a table so the top third of the bag hangs over the edge. Place a book large enough to sit upon on top of the bag. Ask student to sit cross-legged on the book.
Gather the open end of the shopping bag, that is hanging over the table edge, to form a mouthpiece like that found on a balloon. Ask a student to blow into the mouthpiece until the bag inflates, lifting the student sitting on the book off the tabletop. Because the air is spread over a large area, it is able to support the weight of the student. A real world application for this property of air may be found in the hovercraft.
Air particles tend to mix with each other without anything moving them. The scientific term for this property of air is diffusion. Students can discover this phenomenon for themselves using various sources of aroma, blindfolds and several stopwatches. Some possible aroma sources could include: an orange, air freshener, a jar of coffee and a bottle of perfume. Position blindfolded students armed with stopwatches a step apart in a line formed from the front of the room to the back.
Instruct the students how to operate the stopwatches they hold so that they begin to time the project simultaneously on command and stop the watches as they detect an odor in the air. Students are blindfolded so that they are prompted to stop the watches only by their sense of smell. Record times on the stopwatches after each source of aroma is unleashed. Students take turns so that all are given a chance to participate. Results may be recorded in a cooperatively constructed bar graph. Diffusion governs scent and makes certain foods more enjoyable.