The Hot Chocolate Effect: Introducing the Scientific Method

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The Hot Chocolate EffectIntroducing the
Scientific Method
Bradley W. Carroll and Michelle B.
More Weber State University Ogden, UT
Physics
Chemistry
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Science according toScience Educators
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Science according toScience Educators
This is a severe distillation of the scientific
method!
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Painting according toScience Educators
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Painting according toScience Educators
This is a severe distillation of the painting
method!
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Science according toScientists
The scientific method is doing your damnedest,
no holds barred. - P.W. Bridgman
Nobel Prize 1946for high-pressure physics
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The Essential Elementsof the Scientific Method

• Observation
• Hypothesis formation
• Experimentation
• Peer review

are intertwined with curiosity,
inspiration, frustration, tenacity, and lots of
hard work!
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Problem How can we show our pre-service
elementary teachers the real nature of science?
Principles of Physical Science
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The Hot Chocolate Effect
When a spoon is tapped on the bottom of a mug of
freshly made hot chocolate, a tone of constantly
rising pitch is heard.
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The Hot Chocolate Effect intrigues everyone who
hears it!
For 30 years Ive shared it with

• Other science faculty
• Science students
• Students of
• science students

Lori Criswells elementary students
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The Hot Chocolate Effect intrigues everyone who
hears it!

• My yoga class
• You
• Everyone is hooked!
• Named byFrank Crawfordin 1982

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Our First Lab
plus hot water, cold water, milk,
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Students Reactions in Lab
Once I got started,my mind went
crazy with questions.
Our students keep journals as they

• formulate their own questions (make
  hypotheses)
• experimentally seek answers
• modify (or discard) hypotheses based on
  experimental outcome
• share their results (peer review)
• recognize the tentative nature of their
  conclusions
• continue experimenting at home!

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The Day after Lab

• Use students journals to discuss what they did.
• Review their lab comments and identify them with
  the essential elements of the scientific method.
• Hot chocolate context breathes life into the
  textbook scientific method.
• Students really, really, really want to know the
  answer.
• A good mystery is more compelling than a mere
  fact.

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What Causes theHot Chocolate Effect?
It is similar to the sound made by blowing over a
Coke bottle.

• The air above the Cokes surface vibrates with a
  sound wave.
• The hot chocolate below the surface vibrates with
  a sound wave.
• The Coke bottles tone depends on the height of
  the air above the Cokes surface. The less air,
  the higher the pitch.

http//www.phys.ufl.edu/demo/3_OscillationsWaves/C
_Acoustics/CokeBottles.html
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However, the Coke analogy does not explain the
rising pitch of the hot chocolate!
The depth of the hot chocolate does not change
as the pitch rises.

• Tiny bubbles in the hot chocolate lower the
  speed of sound in the liquid by making it more
  compressible (less springy).

Top Secret
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The Rising Pitch

• It takes more time for the sound to travel
  between the bottom of the mug and the surface
  (lower pitch).
• As the bubbles rise and burst, the speed of sound
  increases and the pitch rises.

Explanation due to Frank Crawford, American
Journal of Physics, 1982.