The Child’s Ideas for Grade 4, 3. Liquid Materials
The Challenges of Learning About Liquid Materials
one of the main challenges in teaching children about liquid materials is to help them begin to appreciate some of the deeper similarities they share with solid materials
Since infancy, children have had extensive experience with one important class of liquid materials—drinks—that are essential to their health and well-being. Some of the first names they learn for specific materials are names for such liquids as water, milk, and juice—and they have rich knowledge of their sensory-motor affordances. They know that you need to pour drinks into containers that hold them, that drinks can move from their container to your mouth if you tip them at the right angle but also can slosh around or spill if you are not careful, and that different drinks have different characteristic colors, textures, odors, and tastes. For example, water is colorless, runny, and clear; milk is white and creamy; juices can be different colors, are sweet tasting and sticky to touch. Water, of course, can be found not only in glasses and containers, but outside in puddles, swimming pools, streams, and lakes. Children have still further sensory-motor experiences with this special liquid—immersing themselves in water when they take a bath or swim, or being drenched when outside in a cloudburst. These give rise to their knowledge of another characteristics of water—that water can make them wet.
All of these experiences highlight the distinctive properties of liquid materials—the myriad ways they are different from the more stable, rigid, everyday objects (toys, furniture, cars, trees) that also inhabit their universe. Hence, one of the main challenges in teaching children about liquid materials is to help them begin to appreciate some of the deeper similarities they share with solid materials—that they occupy space, have weight, and can be distinguished by their densities. Such understanding is entr�e for helping them to develop a more abstract concept of matter (that includes both solid and liquid materials) and of material itself (that can be in both solid and liquid forms).
Because liquids are so fluid and changeable, they don't appear to have those constant properties as long as children rely on their perceptual experiences rather than formal measurement in interacting with them. For example, because liquids slip through your fingers when you attempt to hold them, they appear to have no weight. Because liquids change shape so easily as they slosh around or as you pour them from one container to another (which does greatly change the area the liquid covers), it is not obvious that they take up a fixed amount of space across those transformations. Similarly, because objects can be easily immersed in water, it is not obvious that the water itself is taking up space; children tend to think of themselves as simply going into the water rather than the water being displaced.
Still another challenge children confront in learning about liquid materials is more clearly differentiating their concept of liquid from their concept of material. Most everyday liquids that children encounter are water-based drinks, which although they can vary in taste, are similar in their densities and other behavioral properties. Hence, water is the prototypical liquid for children, and it is easy for them to think of water and liquid as synonymous. As they extend their range of experiences—encountering such liquids as oil, alcohol, glycerin or molasses that are not water-based—they strengthen making this fundamental differentiation. Further, as they explore what happens when you cool these materials, they come to the astounding realization that the same material can be in solid or liquid form. Thus, there is an even deeper similarity between solids and liquids—both can literally be the same stuff! Indeed, when material is defined at this abstract level, water (or more properly the H2O molecules that comprise water) isn't even wet!
—Carol L. Smith
