Classroom activity Grade 5 Engineering & Design
Clear the Creek: A Grade 5 Water Filter Design Challenge
A hands-on grade 5 engineering activity where teams layer filter materials to clear simulated muddy creek water, test results, and redesign for a second round.
Objectives
- Students will design a layered water filter using provided materials to meet a stated clarity goal.
- Students will run a controlled second round, changing only their filter design, and compare results to their first attempt.
- Students will explain why a real water treatment plant cannot allow cloudy water to reach a whole town.
Vocabulary
Key words: filter, clarity, layer, fair test
Teacher overview
This is a team-based design-and-test activity for groups of 3 to 4 students. Each team acts as a small engineering team hired to design a filter that clears muddy creek water, using layers of gravel, sand, and cotton or coffee-filter material stacked inside a cup with holes poked in the bottom. The core mechanic maps directly onto real water treatment: each layer removes something different from the water, just as a real treatment plant's settling tanks and sand filters remove different sizes of particles in sequence, and teams that get cloudy results in round one must figure out which part of their design to change before round two.
Every team starts with the same measured sample of muddy water and the same time limit, so results can be fairly compared across the room. The activity ends after every team has completed two rounds and reported a clarity rating, followed by a short discussion connecting the filter model to what happens when a real treatment plant's filters do not work well enough.
Activity Directions
Before class, mix the muddy water: stir 1 cup of garden soil into 1 gallon of water and let it settle for about 10 minutes so the largest clumps sink. Set up team stations, each with an empty cup (holes poked in the bottom), a clean collection cup, small measured piles of gravel and sand, coffee filters or cotton balls, and a 1-cup sample of the muddy water.
Explain the scenario: after a heavy storm, a creek has become muddy, and each team is an engineering team competing to design a filter that produces the clearest water possible using only the materials provided.
Divide the class into teams of 3 to 4. Give each team its station materials and explain the design criteria and constraints: the goal is the clearest possible water; teams may only use the gravel, sand, and cotton or coffee-filter material provided; they may choose the order and amount of each material; and the filter must finish dripping into the collection cup within 5 minutes.
Give teams 5 minutes to plan and build their filter by layering materials inside the holed cup in whatever order they choose.
Each team pours its 1-cup sample of muddy water through its filter into its collection cup, timing 5 minutes for the water to finish dripping through. Remind students not to taste or drink the muddy or filtered water, even if it looks clear, and to wash their hands after handling soil.
Test clarity: hold the printed card with large text directly behind each team's collection cup. If the words are easy to read through the water, the filter earns a "clear" rating. If the words are visible but blurry, it earns a "cloudy" rating. If no words are visible at all, it earns a "very cloudy" rating. Record every team's rating on the board.
Discuss the round 1 results as a class for 5 minutes: which layer orders produced clearer water, and which produced cloudier water? Then give each team a fresh 1-cup sample of muddy water and 3 minutes to redesign their filter, changing at least one thing about their layering based on what round 1 showed.
Teams repeat the pour-and-test process from steps 5 and 6 for round 2. The activity ends once every team has reported a round 2 clarity rating; gather the class together for the debrief.
Student Handout
Each team records its results on a simple chart:
| Round | Layer order (bottom to top) | Clarity rating |
|---|---|---|
| 1 | ||
| 2 |
Debrief questions:
- Did your team's clarity rating improve, stay the same, or get worse from round 1 to round 2? What did you change, and why did you think that change would help?
- If a real water treatment plant let cloudy water reach every home in a town, what problems could that cause?
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
- Debrief question 1 answer: Answers will vary by team, but every response should name a specific change made between rounds (such as moving sand below gravel, adding a coffee filter layer, or using more sand) and connect that change to whether the round 2 rating improved, matching the fair-test idea of changing one variable and observing the result.
- Debrief question 2 answer: A strong response notes that cloudy water can carry disease-causing organisms or other harmful material that settling and filtering are meant to remove, and that an entire town's homes, schools, and hospitals depend on that water being reliably clear and safe, so a treatment plant cannot let cloudy water pass through the way a classroom filter test can.
Differentiation
Support (below grade level)
Provide two pre-built example filters (one with sand on the bottom and gravel on top, one with gravel on the bottom and sand on top) for teams to observe and compare before building their own, so they have a concrete starting point rather than an open-ended choice. Reduce the round 2 redesign step to choosing from two suggested changes written on cards rather than generating an original idea.
Extension (above grade level)
Challenge advanced teams to add a fourth material option, such as a small square of paper towel, and predict in writing, before testing, where in their layer order it will work best and why. After round 2, ask these teams to explain what a real treatment plant does that this classroom filter cannot, such as adding a chemical that clumps fine particles together before they ever reach the sand filter.
ELL supports
Demonstrate the pouring and clarity-testing steps once for the whole class before teams begin, so the process is visible rather than only described in words. Provide picture labels for gravel, sand, and cotton or coffee filter at each station, and allow the debrief chart to be completed with drawings of the layer order in addition to written words.
Extensions
Invite a local water or wastewater treatment operator to visit the class or answer questions by email about how their plant actually removes cloudiness from water, and compare their real multi-step process to the class's one-cup filter test.