The Hot Chocolate Effect: Introducing the Scientific Method Bradley W. Carroll and Michelle B. More Weber State University Ogden, UT PhysicsChemistry

Science according to Science Educators

This is a severe distillation of the scientific method!

Painting according to Science Educators

This is a severe distillation of the painting method!

Science according to Scientists “The scientific method is doing your damnedest, no holds barred.” - P.W. Bridgman Nobel Prize 1946 for high-pressure physics

The Essential Elements of 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 students Lori 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 by Frank Crawford in 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 the Hot 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.

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 chocolate does not change as the pitch rises. Top Secret

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.