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In this fascinating and fun experiment, learners use chemistry to identify a mystery powder and to solve a "crime," a process similar to that used by real forensic scientists. Learners test, observe and record data as they try to determine whether a character used baking soda or another "secret powder" to bake a cake. The answer that is found "proves" whether the character is innocent or guilty. This activity may be combined with other projects related to forensic science, or with a writing activity to create stories about "crimes" that can be solved using science.

Quick Guide

Preparation Time:
30 to 45 minutes

Learning Time:
45 to 60 minutes

Estimated Materials Cost:
$5 - $10 per group of students

Age Range:
Ages 6 - 11

Resource Types:
Activity, Experiment/Lab Activity

English, Spanish

Materials List (per group of students)

  • Data table
  • Pencil
  • Purple grape juice
  • White vinegar
  • Iodine
  • 3 cups, each with 1 teaspoon of baking powder
  • 3 cups, each with 1 teaspoon of flour
  • 3 cups, each with 1 teaspoon of baking soda
  • 3 cups, each with 1 teaspoon of the "mystery substance"
  • 3 pipettes or eyedroppers
  • Paper towels
  • Sticky notes (to use as labels)


  • Physical Sciences
    • Chemistry
      • Chemical Reactions
      • Acids and Bases
  • The Nature of Science
    • The Scientific Process
      • Asking Questions
      • Conducting Investigations
      • Gathering Data
      • Formulating Explanations

Informal Categories

  • Crime Science
  • Food and Cooking


To use this activity, learners need to:

  • see
  • see color
  • be mobile
  • touch

Learning styles supported:

  • Involves teamwork and communication skills
  • Uses STEM to solve real-world problems
  • Involves hands-on or lab activities


Foreign language versions of this resource:

Components that are part of this resource:

Includes alignment to state and/or national standards:

This resource is part of:

Access Rights:

  • Free access


  • WGBH

Source Collection

  • Fetch! With Ruff Ruffman


  • All rights reserved, WGBH Educational Foundation, 2008

Funding Sources:

  • National Science Foundation, 0714741
  • Public television viewers
  • Greendog