TE 407, Sections 3 and 4: Science

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TE 407, Sections 3 and 4 Science

• Charles (Andy) Anderson
• Gail Richmond
• Steve Tuckey
• Brett Merritt
• Dipendra Subedi

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Questions to Answer

• What will happen when the Alka-Seltzer drops into
  the water?
• The bag will rise
• The bag will not go up or down
• The bag will sink
• Why will that happen?

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Most Common Answer from High School Students

• The bag will rise
• Some of the solid Alka-Seltzer is converted to a
  gas, and gases are lighter than solids
• What do you think of this answer?

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What evidence supports the common student answer?

• Gases are lighter
• Solids and liquids fall to the ground gases
  dont
• Some gases make things float
• Air makes things float in water
• Helium and hot air rise

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What evidence supports the common student answer?

• Mass can change
• Most properties of substances can change without
  having to go anywhere
• Temperature
• Volume
• Shape
• Color
• Mass is like those other properties
• People gain and lose weight
• Trees grow from seeds
• Things burn up
• Liquids evaporate

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How do people change their minds?

• Arguments from authority
• Learn these facts
• They are right and you are wrong
• Arguments from evidence
• My theory predicts and explains what we observe
  in the world better than your theory

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What are the arguments from evidence?

• Gases have mass
• Mass is conserved

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A Couple of Things to Notice about Tuesdays
Discussion

• Sharing your own ideas is scary--especially if
  you are used to science classes where all that
  counts is the right answer. (So thanks for being
  willing.)
• Practicing right answers that consist of a word
  or a number or the right multiple choice doesnt
  completely prepare you to teach the content
• Students ideas are interesting.

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Big Problem for Science Teaching (Teaching for
Understanding)

• How do we get students to believe and use
  scientific theories that contradict lived
  experience?

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Another Big Problem for Science Teaching
(Teaching for Motivation)

• How do we get students to make the effort it
  takes to learn with understanding?

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Thursday Properties of Substances

• Changing from heaviness and amount to mass,
  volume, and density

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Each Group of 4 Candidates Needs

• 5 vials
• Cups of each color of solution
• Waste cup
• 4 droppers
• 4 soda straws

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Key Questions about Colored Solutions

• What stacks of solutions are possible?
• Are any stacks impossible?
• Is it possible to make different stacks by
  different techniques?
• In the vials, vs. droppers, vs. soda straws
• By using different amounts of liquid
• Why?
• How is this activity connected with the
  Alka-Seltzer demonstration?

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Comparing Student and Scientific Ideas about Mass
and Density

• Student ideas Heaviness as a property of matter
• Objects and materials can be light or heavy
• Balance scales and floating/sinking both compare
  heaviness
• Qualitative scientific ideas Mass and density as
  properties of matter
• Mass (extensive) is a property of objects
• Density (intensive) is a property of materials
• Balance scales compare mass
• Floating and sinking compare density
• Quantitative scientific ideas
• Spring scales and balances measure mass (weight)
• D M/V Weighing measured volumes of substances

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Question Do the colored solutions activities
lead you to change your prediction for the
Alka-Seltzer demonstration?
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Tuesday Wrapping up Alka-Seltzer and Colored
Solutions
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How do people change their minds?

• Arguments from authority
• Learn these facts
• They are right and you are wrong
• Arguments from evidence
• My theory predicts and explains what we observe
  in the world better than your theory

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Evidence-based Arguments that Floating and
Sinking Depend on Density, Not Weight

• Floating heavier substances on top of lighter
  ones (e.g., lots of red on top of a little green,
  glacier on top of a layer of water)
• Comparing different amounts of more and less
  dense substances
• Comparing equal amounts of more and less dense
  substances
• Quantitative scientific relationship D m/v

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Experiences, Patterns, and Explanations
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Question Do the colored solutions activities
lead you to change your prediction for the
Alka-Seltzer demonstration?

• Is this a demonstration about MASS (qualitatively
  compared with balances) or about DENSITY
  (qualitatively compared by floating and sinking)

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Experiences, Patterns, and Explanations for
Colored Solutions
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Relating Properties of Substances to Forces

• How do we understand the relationship between
  forces (which we can measure and detect) and mass
  (which we cannot measure or detect)

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Measuring or Comparing Mass

• Spring scale measures force
• Balance compares forces (weights)

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Comparing Density

• Qualitative pattern less dense materials float
  in more dense materials
• Qualitative explanation Why?
• One explanation
• Balance of forces
• Force pressure x area
• Compare pressure on top and bottom of submerged
  object or fluid

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Scientific Quantitative Patterns Archimedes
Principle

• What is the size of the buoyant force?
• Buoyant force weight of displaced fluid
• Buoyant force density of displaced fluid x
  volume of object
• Three key variables
• weight of object ( volume x density of object)
• density of displaced fluid
• volume of object

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Questions to Answer

• What will happen when the Alka-Seltzer drops into
  the water?
• The bag will rise
• The bag will not go up or down
• The bag will sink
• Why will that happen?
• What predictions would you expect students to
  make, and why?

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Notes for Science Teachers

• Being articulate about the answers to the why
  questions is important
• Being able to answer the third question is as
  important as being able to answer the first two
• Arguments from evidence are important
• Evidence has to be convincing to STUDENTS
• Look for new experiences that will help them to
  see new patterns (incorporating both old and new
  experiences)

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Investigating Buoyant Forces on Objects Denser
than the Fluid

• Using a balance to compensate for extra weight
• How can we change the three key variables
  individually?
• Density of fluid
• Weight of object
• Volume of object
• These are experiments that support arguments from
  evidence

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Conservation of Mass in Air

• When a solid or liquid turns into a gas in air.
• What happens to the mass?
• What happens to the weight?
• What happens to the measured weight?

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Instructional Representation for Buoyancy
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Challenges for Student Understanding

• Properties of materials
• Conservation of mass in changes involving gases
• Confusion of weight/mass and density heaviness
• Colored solutions
• Weighing colored solutions
• Density column
• Confusion of weight/mass and volume amount
• Displacement volume
• Forces on materials and measuring weight in fluid
  media
• Explanations for floating and sinking
• Balance between buoyant force and weight
• Size of each force density x volume
• Buoyant forces on objects denser than the medium
• Washer demochanging medium
• Alka-Seltzer demochanging volume
• Removing water demochanging weight