A mysterious toxic spill has cursed the Haunted Swamp! Your class of scientists has been summoned by the local town council to design and build a filtration system that can rescue the swamp’s ghostly residents before Halloween night. Each team must engineer, test, and optimize a filter that clears “swamp sludge” (murky dyed water) while keeping costs low and efficiency high.

Bring spooky season into environmental engineering! In this hands-on STEM challenge, teams design and refine a gravity filter to “rescue” a haunted swamp. Students budget for materials, build and test prototypes, measure water clarity, and use evidence to justify the most effective design—all in one engaging STEM activity.

You can also find this activity at a discount inside my - Halloween Science Activities and Investigations Growing Bundle.

What students will learn

• How mechanical filtration (gravel/sand) and adsorption (activated charcoal) remove contaminants
• How to plan a fair test and control variables (layer order, seal quality, flow rate)
• How to collect and interpret quantitative data (time-to-filter, turbidity/clarity)
• How to argue from evidence with a clear CER about the best design under a budget constraint

Classroom flow (45–70 minutes)

1. Hook & safety (goggles, no tasting, tidy stations)
2. Design & budget with a $10 “materials store”
3. Build → test → iterate with one change per trial
4. Analyze & explain: complete the CER and compare designs against success criteria (clarity, speed, stability, cost)

What’s included

• Teacher Guide with setup, safety, pacing, success criteria, and a complete Haunted Swamp Water recipe with step-by-step instructions and shopping list.
• Student Handout: roles, planning sketch page, budget table, trial log, results summary, turbidity rating chart (0–5), and CER prompts
• Answer Key for analysis questions (which layers catch solids vs remove color, why order matters, and model CER)
• Detailed Analytic Rubric: safety, design & constraints, build quality/sealing, data quality, performance vs criteria, iteration, and CER communication

Materials

Coffee filters, sand, gravel, activated charcoal, cotton/felt, rubber bands, tape, 2L bottles/funnels, cups/beakers, timer, turbidity chart, and the prepared “swamp” water. Use the included $10 budget menu to drive authentic engineering tradeoffs.

Why teachers love it

• Seasonal Halloween theme that boosts buy-in—without sacrificing rigor
• Clear criteria keep teams focused and on task
• Real data + real constraints = authentic engineering design
• Flexible timing; works in a single period, but supports deeper iteration and discussion

Teacher prep at a glance

Mix the Haunted Swamp Water (recipe included), set up the Materials Store with labeled prices, print student pages, and you’re ready. Students do the rest—designing, testing, and optimizing their way to a cleaner swamp before Halloween night!

Tip: Pair this with a hallway display—“Before & After: Swamp Water Makeover”—featuring student turbidity ratings, times, and budget totals.

NGSS alignment

• MS-ETS1 Engineering Design (defining problems, testing solutions, optimizing designs)
• Science & Engineering Practices: Planning and Carrying Out Investigations;
• Analyzing and Interpreting Data; Using Mathematics and Computational
• Thinking; Engaging in Argument from Evidence
• Crosscutting Concepts: Cause and Effect; Structure and Function