Developmental Lesson FC #2.1:
Pressure and the Structure of Ice - Demo
Teacher Notes and Materials
2.1: Describing Changes
Goal Facet 03: The student understands that environmental conditions such as temperature
and pressure are responsible for changes in the arrangement and motion of small particles.
Overview:
This lesson can be performed as a demonstration or a class activity. Students will examine the
effect of the environmental condition, pressure, on a solid. The lesson investigates the effects of
pressure from a wire, weighted by a large bottle, on an ice cube.
Materials:
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2-liter soda bottle
32-gauge rust-resistant craft wire
Ice cube
Fork
C-clamp (to mount fork to table or desk) – a stack of books can be used instead
Drainage collection pan (for water drops from the melting ice)
Purpose
The purpose of this activity is to examine the effect of pressure on the melting of ice.
Preparation/ Demonstration
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Fill 2-L bottle with water.
Make a loop of wire to hang bottle on ice cube.
Arrange mount on table to suspend fork above pan.
Place ice cube on fork.
Hang filled bottle from ice cube by fine wire loop.
Ask students to post multiple working hypotheses as to the likely outcome.
Wait ~15 minutes while discussing principles of pressure melting.
Discussion Questions
1) Predict what will happen to the ice and wire system.
2) What do you think is happening to the ice at the molecular level?
Developmental Lesson FC #2.1:
Pressure and the Structure of Ice - Demo
Teacher Notes and Materials
Background:
Pressure can affect the structure of liquids and solids. For most
liquids, as you increase the pressure at a constant temperature it will
eventually undergo a phase change to become a solid as the
molecules are forced closer and closer to each other. However, in
some cases, such as water, due to the unique crystal structure of the
solid phase, adding pressure has the opposite effect and will cause
the solid to liquefy. This happens when the pressure is great enough
to break the intermolecular forces holding the molecules together.
3) Illustrate what is happening to the ice at the particle level.
Developmental Lesson FC #2.1:
Pressure and the Structure of Ice - Demo
Teacher Notes and Materials
Teaching Notes and Tips
Activity taken from:
http://serc.carleton.edu/sp/compadre/demonstrations/examples/pressure_melt.html
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Wire cuts through ice cube (pressure melting).
Ice refreezes behind it (regelation).
Melting cube can be picked up and held by one end.
A septum of bubble-free regelation ice marks the healed track of the wire.
The amount of water does not have to be exactly 2 liters, however it will take longer for the wire to
go through the ice if you have a lighter load on it. Other bottles will work. For example a bottle
with a handle works nicely because you can loop the wire through the handle.
It requires about 30 minutes for the wire
to cut through a standard ice cube. Finer
wire would cut faster (but break even
more frequently) as would a heavier load.
Although the ice cube shrinks in the
process, there is typically enough left to
do a second pass.
As the demonstration is proceeding you may have students pose multiple working hypotheses as to
the outcome of the experiment.
Ice structure image taken from:
http://ssrl.slac.stanford.edu/nilssongroup/pages/project_liquid_structure.html