Mystery Bottles
Summary
The "Mystery Bottles" activity engages students in scientific inquiry by challenging them to determine the contents of opaque black jars filled with unknown materials. Students propose investigative methods, gather observational evidence, make predictions, and formulate hypotheses. This exercise emphasizes the process of science and develops skills in observation, inference, and critical thinking.
Keywords: scientific method, hypothesis testing, inquiry-based learning, physical geology, observation, prediction, introductory geoscience, icebreaker.
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Context
Audience
This activity is used in an introductory physical geology course designed for undergraduate non-majors and majors. However, students at any level can easily tackle this activity.
Skills and concepts that students must have mastered
No prior geology knowledge is required. Students will be able to make basic observations, record qualitative data, and understand the concept of hypothesis generation.
How the activity is situated in the course
The activity is a stand-alone exercise used as an icebreaker and foundational lesson on the scientific method and critical thinking. I typically give this in the first or second class.
Goals
Content/concepts goals for this activity
Introduce the scientific method and hypothesis formulation
Explore how geoscientists investigate materials and processes indirectly
Understand the distinction between observation and inference
Higher order thinking skills goals for this activity
Develop testable hypotheses based on limited data
Analyze sensory observations to draw conclusions
Critically evaluate multiple possible explanations
Skills goals for this activity
Practice collaborative problem-solving
Communicate observations and reasoning effectively in small groups
Build confidence in scientific reasoning in a low-stakes setting
Description and Teaching Materials
Each group of students receives a blacked-out plastic bottle containing a different "mystery" substance. I use dirt, pebbles, broken glass, syrup, soapy water (particularly challenging), sticks/mulch, flour, putty, etc. Basically anything that is cheap or free and fits well in the jars. Students are told not to open the bottles but to use non-destructive methods to collect data.
The instructor guides students through a three-part task:
Propose a list of tests or observations that might help identify the contents (I give them an unlimited budget and tools)
Carry out those tests that they can and record data or observations
Make a prediction and formulate a hypothesis about what's inside
After discussing findings as a class, students reflect on the differences between evidence, inference, and hypothesis, reinforcing how geologists interpret Earth materials without always being able to "see inside." Materials needed include opaque plastic bottles (I have found that 8oz black plastic work well- https://www.amazon.com/250-Wide-Mouth-rhinestones-Cosmetics-KUKLIPJIM/dp/B0D22Q7VD3) and a variety of fill materials with distinct properties.
Student Handout for Mystery Bottles (Microsoft Word 2007 (.docx) 40kB Jun4 25)
Assessment
Student learning is assessed through informal group discussion to gauge engagement, critical thinking, and collaboration. Instructors also assess a brief written response turned in at the end of the activity. The primary focus is on the process rather than correctness of the final answer.