The Hot Chocolate Effect:Introducing the Scientific Method

Bradley W. Carroll and Michelle B. More

Weber State UniversityOgden, UT

Physics Chemistry

Science according toScience Educators

Science according toScience Educators

This is a severe distillation of the scientific method!

Painting according toScience Educators

Painting according toScience Educators

This is a severe distillation of the painting method!

Science according toScientists

“The scientific method is doing your damnedest, no holds barred.” - P.W. Bridgman

Nobel Prize 1946for high-pressure physics

The Essential Elementsof the Scientific Method

• Observation

• Hypothesis formation

• Experimentation

• Peer review

are intertwined with curiosity, inspiration,frustration, tenacity, and lots of hard work!

Problem: How can we show our pre-service elementary teachers

the real nature of science?

Principles of Physical Science

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.

The Hot Chocolate Effect intrigues everyone who hears it!

• Other science faculty

• Science students

• Students of

science studentsLori Criswell’s elementary students

For 30 years I’ve shared it with:

The Hot Chocolate Effect intrigues everyone who hears it!

• My yoga class

• You

• Everyone is hooked!

• Named byFrank Crawfordin 1982

Our First Lab

plus hot water, cold water, milk,…

Students’ Reactions in Lab “Once I got started,my mind went crazy with questions.”

• 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!

Our students keep journals as they

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”.

What Causes theHot Chocolate Effect?

It is similar to the sound made by blowing over a Coke bottle.

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

http://www.phys.ufl.edu/demo/3_OscillationsWaves/C_Acoustics/CokeBottles.html

However, the Coke analogy does not explain the rising pitch of the hot chocolate!

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

The depth of the hot chocolatedoes not change as the pitch rises.

Top

Secre

t

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.