Why is this science?
There are several features of what the students are doing that make it a clear example of science.
First, the students are working to reconcile an inconsistency between the model they’ve been working with and their observations of the world. They consider different options for reconciling the inconsistency: (1) some students tweak the existing model in ways that more closely align with their observations (Jack A and Ben), and (2) other students conjecture that the expansion they observe when water freezes may be a special case when the water is in close proximity to air (Inger’s idea).
Second, students cite evidence and propose experiments to support their conjectures. For example, DC says, “You guys know when you put your cup full of water, and then you put ice cubes in it and they crack- the ice crack? That’s the- that’s the um air pockets opening,” to support the idea that air might be getting trapped between the water molecules. Megan proposes a hypothetical scenario to determine whether the presence of air is responsible for the expansion: “If like you had a water bottle with like somehow you had no air in it if it would still like [expand].”
Finally, Jack B, in particular, continuously pushes Ben and Jack to explain why water expands when it freezes. He believes that a their model should provide a mechanism for the phenomenon, not just an account of it.
What contributed?
Various aspects of what was going on contributed to initiating and sustaining this episode.
The students recognizing an inconsistency between model and experience
The central question that students are grappling with emerges from an
inconsistency between their model and their experience. The model
predicts that hotter molecules move farther away from each other and
colder molecules move closer together. However, their observation
contradicts this prediction–water expands when frozen! This
inconsistency proves to be genuinely problematic for students,
especially Jack A and Ben, who attempt to add new features to the
existing model as a way to reconcile the inconsistency. Ben develops a
model in which molecules merge together and then buckle to form pockets
and Jack A develops a model in which air pockets get trapped between the
molecules as they join together to form ice.
Tension around and refinement of the question
From the beginning, there seemed to be disagreement over the nature of
the problem. Jack A argued that packing together makes something
smaller, which raised the question of how water “packing together” to
make ice could be larger. DC argued for a simple solution, with the
analogy that people huddled together form a larger unit. This tension
drove students to focus on articulating the problem itself.
Students’ agency over the flow of the conversation
From the start, we see students taking agentive roles in leading the
discussion and determining who gets the floor to speak and who their
audience is: they authored ideas and initiated questions, they
interacted directly with each other’s ideas, evaluated each other’s
arguments, negotiated the nature of the controversy, and refocused the
conversation. This agency was both taken by the students and granted by
the teacher.
Availability and use of material resources
Students used various physical resources as they reasoned about the
question. They used the board to draw and communicate ideas. They had
sheets of paper and notebooks to use in constructing models. Ben, for
instance, demonstrated his idea with two notebooks (representing
molecules): he brought the notebooks close together then bended them to
create an empty space in between them (representing the air pockets in
ice). Jack A crumpled a piece of paper to illustrate his idea of how air
gets trapped as the molecules get closer together.
The teacher made space for students’ ideas
Most of the time during this episode, Mrs. Filner, who was sitting in
the back of the room, was listening to the students and allowing them to
lead the discussion. They, in turn, seemed comfortable addressing each
other without her facilitation. Occasionally, she directed the
conversation, to focus attention on a particular student. She also
joined in to articulate the essence of a debated issue, such as when the
students wrestled over whether packing together makes something larger
or smaller: “But if we all squished ourselves together, I don’t think we
all of a sudden are bigger!”
Students’ strong feelings
In several ways, students’ feelings seemed to motivate their
participation and to be part of their communicating their positions in
the debate. To start, Jack A’s puzzlement drove his persistence in
posing and articulating the question, and it communicated to others that
there was something he was genuinely trying to understand. Students
also showed irritation, Jack A over students not understanding his
question and Jack B over the lack of mechanism in Ben’s explanation:
“But then how does it exPAND like what you’re saying?” And they showed
excitement, such as Ben in declaring, “I need two pieces of paper.”