Turn your students into science detectives with this NO PREP, engaging, real-world investigation focused on water purification and treatment systems. In this case file activity, students analyze water quality data, examine filtration results, evaluate settling processes, investigate chemical treatment effects, rank possible causes, and build a scientific case to solve the mystery of how contaminated water becomes safe to drink.

Instead of passively learning about filtration and water treatment, students actively investigate, analyze patterns, and reason through the evidence to uncover how physical filtration, settling, and chemical disinfection work together to remove contaminants. This activity makes an important real-world chemistry topic interactive, engaging, and easy to understand while strengthening critical thinking and literacy skills.

✅ NO PREP, no formatting, no issues. Simply download and go. Includes all instructions, answer key, rubric, and background reading students need to solve the case. This mystery is included inside my Chemistry in Everyday Life Mystery Activity Bundle.

10-Part Activity Breakdown

Part 1 – Mission Briefing:
Students are introduced to a case involving contaminated water that contains visible particles, dissolved substances, and possible microorganisms that must be removed before it is safe to drink.

Part 2 – Background Reading:
Students build foundational knowledge about filtration, settling, chemical treatment, and how multiple purification steps work together to clean water.

Part 3 – Evidence Log:
Students examine 10 detailed evidence cards related to cloudy water samples, particle settling, sand filtration, activated carbon filtering, fine membrane filtration, chemical disinfection, lab testing results, and multi-step purification systems.

Part 4 – Suspect Ranking:
Students rank possible explanations (filtration removing particles, settling of heavy particles, chemical treatment disinfecting water, fine filters trapping microscopic contaminants, multiple purification stages working together) and justify their reasoning using scientific evidence.

Part 5 – Pathway Tracking:
Students trace how contaminated water changes through each stage of treatment → settling → filtration → disinfection → clean water.

Part 6 – Impact Analysis:
Students analyze how purification affects water quality, environmental health, and human health.

Part 7 – The Big Question:
Students explain how filtration and treatment processes work together to remove contaminants and produce safe drinking water.

Part 8 – CER Writing:
Students construct a scientific argument using Claim–Evidence–Reasoning.

Part 9 – Solutions & Action Plan:
Students propose personal, community, and engineering solutions to improve water quality and protect water sources.

Part 10 – Reflection:
Students reflect on the importance of clean water and how human actions impact water systems.

What Students Will Learn

• How filtration removes solid particles from water
• How settling helps separate heavier contaminants
• How chemical treatment kills harmful microorganisms
• Why multiple purification steps are needed
• How different contaminants require different removal methods
• How water quality is tested and monitored
• How physical and chemical processes work together
• How to use Claim–Evidence–Reasoning (CER) to support scientific explanations
• How clean water systems protect human health and ecosystem

This activity blends chemistry, physical science, environmental science, critical thinking, and literacy skills into one high-interest, structured lesson that keeps students thinking like real-world scientific investigators.

You can find this Mystery Activity as well as the others I have created inside my Chemistry in Everyday Life Mystery Activity Bundle at a significant discount.

This Mystery Is Perfect for:

• Chemistry in Everyday Life units
• Water systems & human impact lessons
• Environmental science units
• Middle school science classes
• Sub plans, review days, or project-based learning

No prep, no formatting, no issues.

Simply download, print (or upload to your class site) and you're all set.

What’s Included

• A complete student case file with guided worksheets for every step of the investigation
• 10 detailed evidence cards based on real-world chemistry issues --> Evidence cards include two versions: one with images and one without images
• A full teacher answer key with sample responses and grading support
• A full marking rubric that covers all key aspects of the mystery activity

Why Teachers Love This Resource

• Fully structured and print-and-go – Everything is ready to use with clear directions and built-in scaffolding
• High engagement without extra classroom management – The detective format naturally hooks students
• Real-world relevance students immediately understand
• Builds both science and ELA skills – Includes analysis, explanation, and CER writing
• Flexible for any schedule – Use in one class period, over two days, or as a mini-project

Time Required

• 2 class periods
• Can be extended into a 3-day mini-project

The following Mystery Activities can be found inside my Chemistry in Everyday Life Mystery Activity Bundle.

1. The Acid Rain Mystery
2. The Household Cleaning Products Reaction Mystery
3. The Conductivity Case Mystery
4. The Energy Release Mystery
5. The Phase Change Puzzle Mystery
6. The Missing Mass Mystery
7. The Ozone Layer Mystery
8. The Plastic Breakdown Mystery
9. The Solubility Surprise Mystery
10. The Spoiled Food Mystery
11. The Air Quality Alarm Mystery
12. The Density Disaster Mystery
13. The Magnetic Mix-Up Mystery
14. The Rising Dough Mystery
15. The Rusting Metal Mystery
16. The Water Purification Mystery
17. The Unknown Substance Mystery
18. The Hard Water Problem Mystery
19. The Particle Motion Mystery
20. The Temperature Change Mystery

Google Classroom and Distance Learning Ready

• This resource is perfect for in-class or distance learning and integrates seamlessly with Google Classroom.
• It automatically creates a copy of the reading and places it directly into your Google Drive with a single click.
• Purchase → Open → Click → Assign to your students
• The reading also includes a Microsoft Word and PDF version.
• Having all three options allows you to assign the activity without worrying about formatting issues, and ensures access for all students regardless of device or learning environment.

No prep, no formatting, no issues. Simply download, print (or upload), and you're all set.

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If you have any questions please feel free to send me an email - devon@teachwithfergy.com