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Session 3. Physical Changes and Conservation of Matter
Dissolving activity preparation. |
Learning Goals
During this session, you will have an opportunity to build
understandings to help you:
- Matter is neither created nor destroyed during
physical changes.
- Physical changes rearrange, but do not change
particles.
- Under everyday conditions, physical changes are reversible.
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Video Overview
In everyday life, observations that things “disappear” or “appear” seem
to contradict one of the fundamental laws of nature: matter can be neither
created nor destroyed. This session explores various manifestations of
the law, and builds on the particle model of matter to explain physical
changes.
Video Outline
What happens when sugar is dissolved in a glass of water?
When a pot of water on the stove boils away? Do things ever really “disappear”?
The video opens with children in the Science Studio observing a common
magic trick in which matter seems to disappear. As they try to follow the
button that vanishes from their field of vision, the ideas they express
about “where things go” become the recurrent theme as they
and other children explore what happens to matter through a series of physical
changes like melting, mixing, and dissolving. Which principles of the particle
model apply to these changes?
We continue in the Science Studio where two
students investigate the principle of conservation
of matter using building
blocks and the evaporation of
alcohol, and other children grapple with the reversibility of physical
changes.
Technicians Ark Pang and Peter Schuerch introduce us to the
desalination of water, a real-world application of the separation of solutions.
We then
visit the Benjamin Banneker Charter School in Cambridge, Massachusetts,
where Rosinda
Almeida’s second graders are exploring the effect of
heat on the dissolving process. The session ends with a puzzle—how
can the volumes of two liquids that are mixed together and shaken decrease,
while their weight remains constant before and after the shaking? View the video ==>
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