Educational Leadership - September 2015

perceptions shaped by their experiences. In my daughter’s case, experiences gathered at the hospital, grocery store, and local mall had molded her perception.

Our students’ perceptions, and the experiences feeding them, are as diverse as their backgrounds. The difficulty comes when students’ experiences have produced misconceptions that conflict with concepts we’re trying to teach. If we aren’t aware of these misconceptions, we may set students up to run into the proverbial closed door.

The gateway to effectively uncovering and changing students’ misconceptions is predictive questioning. This strategy, used in conjunction with strategic discourse, is a powerful tool (Chin, 2007). Learning, especially the type of inquiry-based learning encouraged in science classrooms, is a socially mediated endeavor.

Inquiry loses its punch without strategic discourse, whether that discourse is with the teacher or among students (Abell & Lederman, 2010). To get a sense of how using predictive questions to uncover misconceptions works, let’s examine a lesson I recently taught my 12th grade astronomy students.

Busting Myths About Gravity

I hoped this lesson would lead students to an understanding of the evidence for dark matter in space.

I wanted them to understand that the amount of gravity in our galaxy isn’t enough to account for the high orbital velocities of the stars near the galaxy’s edge. Even stranger, stars moving at those high velocities should be escaping the galaxy’s collective gravity and flying off into space—yet they stay in their orbits. This implies that something besides the visible mass we can detect in our galaxy is holding the galaxy together.

Before students could understand this “missing mass” dilemma, they had to have a foundational understanding of gravity. The lesson started with helping them grasp the law of universal gravitation, which tells us that the force of gravity (F) is affected by two things: mass (m) and proximity (r). The force of gravity gets stronger if objects have more mass and if objects are closer together; the converse of each statement is also true.

Students needed to understand that
gravity acts as a tether holding objects
together, that objects can overcome
their gravitational tether when they
achieve high enough velocities, and
that the gravitational effects we see
within galaxies can’t be accounted for
by looking solely at the mass from
luminous matter (matter that can
be detected on the electromagnetic
spectrum). I used carefully planned
questions to lead them toward these
understandings.

I began by asking each student to predict the orbital velocities of something familiar to them—the planets in our solar system (What happens to the orbital velocity of the planets as they get farther and farther from the sun?).

I also asked them to explain their reasoning, providing a graphical as well as verbal explanation; they would later observe data on these orbits and revise their explanations as necessary.

These questions were folded into a protocol that I call the predict– explain–observe–revise cycle—modified from White and Gunstone’s (1992) predict–observe–explain strategy.

Students predict the outcome of a potentially discrepant event; explain their reasoning (including graphically if they are looking at the relationship between variables); observe the actual phenomenon or data; and engage in strategic discourse in small groups— which leads them to revise their explanations based on the evidence.

As I expected, most students predicted that orbital velocities would increase as planets got farther from the sun, giving explanations similar to that shown in Figure 1. In physics class, they had learned about linear velocity, which explains that when an object spins around, the outside part of that object spins faster than the inner part. I suspected I would have to reveal—and break down—students’ misconceptions so they would realize that this principle doesn’t apply to the individual orbits of planets and stars.

Next, students collected and observed and graphed actual data on the orbital velocity of our planets.

Finally, in small groups they evaluated this data, talked together about what might explain it, and revised their explanations for the orbital velocities.