The Child's Ideas for 4. Air, a Gas

The Challenges of Learning About Air and Other Gases

when children are asked to put together the things that are alike in that “they are matter or made of some physical stuff,” they almost never group air with solids or liquids

Many children from a very early age have heard about air and know that it is very important. For example, I remember my 3-year-old daughter was shocked to learn that during pregnancy, she was entirely inside me—that her head wasn't somehow sticking out of my tummy—as she exclaimed (with worry), “But how did I breathe?” She knew, even then, that air exists and that it is very important—that she needed air to breathe.

The challenge in teaching children about air (and other gases) then is not simply making them aware of its existence or importance, but giving them a deeper appreciation for what type of thing it really is. To come to see air (or other gases) as a form of matter requires not only developing a general concept of matter, but also reconceptualizing matter as something that occupies space and has weight, and learning that air and other gases share these properties.

Children, of course, know much more about the world of everyday objects—toys, animals, vehicles, clothing, furniture, food—and liquids, especially those that they drink—water, milk, and juice. But these objects and liquids seem to be fundamentally different from air given their appearances and how they behave. Consider: Objects are things that you can see, feel, touch, and hold in your hand. They have heft; they take effort to hold and move. When you let go of them, they drop to the floor. Objects also take up space. In contrast, air is different. Air is invisible and odorless—something that you cannot see, feel, touch, or hold in your hand. Air doesn't have heft or appear to take up any space.

Thus, it is not surprising that when children are asked to put together the things that are alike in that “they are matter or made of some physical stuff,” they almost never group air with solids or liquids. Indeed, when I asked my daughter that question when she was six, she laughed and said “Of course not—you can't see air or feel it or touch it.” For her, air was prototypically non-material, something she grouped with other immaterial things like heat, light, shadows, dreams, and ideas. (Heat and light actually gave her more pause than air because you could feel heat and see light; she ultimately concluded these were not matter too because what was critical was to have a confluence of perceptual cues—seeing, feeling, AND touching in order to be matter.) These ways of responding are typical for elementary school (and many middle-school) students.

We can't simply tell children “matter comes in three phases—solid, liquid, and gas” and expect them to understand. And we can't “simply wait until they are old enough to understand,” as children don't magically become ready to accept air is matter at a certain age. Rather, the solution is to realize that we need to prepare the ground in indirect ways for their learning that air is matter: by helping them elaborate on their ideas about solid and liquid materials and their properties, including that they have weight and take up space. This is exactly what the learning progressions approach of the Inquiry Project aims to do.

—Carol L. Smith