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Session 5. Density and Pressure
Pull meter. |
Learning Goals
During this session you will have an opportunity to build
understandings of the following concepts:
- Rising and sinking are dependent on one essential property—density.
- The density of an object can be explained by the arrangement and weight of its particles.
- Pressure in a fluid acts in all directions, increases with depth, and can be explained by the motion of particles.
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Video Overview
What makes a block of wood rise to the surface of a bucket of
water? Why do your ears “pop” if you swim deep underwater? In
this session, we will examine density, an essential property of matter. We
will also look at how particles of matter are in constant motion, leading
to a deeper understanding of fluid pressure. Finally, we will investigate
the concepts of pressure and density to explain the macroscopic phenomenon
of rising and sinking.
Video Outline
Session 5 begins with a question about how hard one needs
to push a beach ball to get it to go to various depths in a swimming pool.
Does the force required vary? We then observe children in the Science Studio
expressing their ideas about the factors that determine whether an object
sinks or floats in water. As they eliminate weight and shape, they start
to ask what other property might reliably account for whether something
sinks or floats.
We begin to explore the concept of density, what
it looks like on the particle level, and what effect it has on whether something
floats or sinks in a
fluid. How does density fit into Aristotle’s accidental and essential
properties?
Next, Steve Bailey at the New England Aquarium explains how
some fish are able to adjust their density to maintain the neutral
buoyancy they
need
when they aren’t swimming. To see how the concept of density
might be addressed in an elementary level classroom, we look in on
researcher
and teacher Tina
Grotzer as she introduces the Understandings of Consequence/Project
Zero’s Causal Patterns in Density curriculum to Nicole Scalzo’s
class in Arlington, Massachusetts. The students share their microscopic
models, showing the difference between brass and aluminum cylinders
that have an equal volume. Their prior ideas about density provide
a springboard
for further discussion.
We end the session in a swimming pool, where
we take an “in-depth” look
at fluid pressure through the eyes of our Science Studio children,
and return to the questions posed at the outset of the program to find
some
surprising answers. View the video ==>
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