Science Class THE NATURE OF GASES (GRADES 6-8)

Over the past 10 years, the Investigators Club (I-Club) has sought to bridge what students already know about science and what they learn about science in school. The I-Club has been used in a variety of after-school and in-school settings. In its original design, the I-Club is an after-school program, meeting three times a week with students from a wide range of cultural and linguistic backgrounds, predominantly students from low-income families who are struggling or failing in school. It has since been expanded to include an in-school program in middle schools, as well as a prekindergarten curriculum. The following case involves 25 seventh- and eighth-grade students participating in an I-Club after-school program.


Richard Sohmer directs the Investigators Club program, which meets for 15 weeks each school term. There are no special tests or grade requirements for participating in the program, but students in the program have to commit to attending regularly, be respectful of one another, and work hard “to discover, practice, and acquire the skills of scientific investigation.”

Mr. Sohmer’s students were investigating air pressure and the nature of gases and were about midway through their investigation. Prior to this time, the students had begun learning about balanced and unbalanced forces.

In order to demonstrate concepts related to balanced and unbalanced forces, Mr. Sohmer had had two students stand on either side of him and push him hard but with equal force. Despite their efforts, he hadn’t moved. He had then instructed the student on his left, at the count of three, to take a step back, while the student on his right kept pushing. The result was that Mr. Sohmer had stumbled to the left, nearly falling down.

The demonstration had generated a discussion about how objects that were stationary had forces acting on them, but that these were balanced forces. The students had also explored the difference among the three phases of matter: solid, liquid, and gas. They had investigated how phases of matter stem from the interaction of molecular speed and intermolecular attraction.

It was at this point in their investigation that Mr. Sohmer introduced the students to a number of demonstrations, all of which involved everyday materials that the students were familiar with and which they could take home and share with their families. With each demonstration, the students predicted what would happen or attempted to explain what had caused the demonstration to work the way it did.

Over the years, he had found it difficult to disabuse his students of the notion of suction and vacuums as useful explanatory devices. Even though his students knew that air molecules don’t stick together and can’t hook onto anything and therefore can’t pull anything, they routinely invoked the idea of suction. To help his students adjust their view of how air pressure worked, Mr. Sohmer came up with an analogy, a narrative form of the ideal gas law, that he called the “Air Puppies” story.

Mr. Sohmer drew a large rectangle on the blackboard. He told his students to pretend that they were looking down at a large room.

“In this room is a special wall that divides the room into two parts. The wall is on roller blades, the kind with really good wheels, so it’s practically frictionless.”

Mr. Sohmer drew a line down the middle and showed the roller blades in red. He said: “The wall can move easily, to the right or left, if something touches it. So if I were standing on the left side of



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