Lesson plan Grade 4 Engineering & Design

Cleaning Willowmere's Muddy Water: A Two-Step Treatment Design

A grade 4 lesson where students design and compare the order of two cleaning steps, settling then filtering, to clear a fictional river town's muddy water.

Grade: Grade 4
Subject: Engineering & Design
Material: Lesson plan
Time: 45 min
Prep: Low prep
Materials: 2 clear jars, Muddy water sample (soil stirred into water), Coffee filter, Spoon, Process-order cards, Chart paper, Index cards (1 per student)

Standards

3-5-ETS1-1 NGSS

Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.

How this material aligns: Students define what clean water means for Willowmere as a success criterion and name the constraint that the filter must not clog, the problem-defining work this standard requires.

All materials for 3-5-ETS1-1 →

3-5-ETS1-2 NGSS

Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.

How this material aligns: Students compare two possible orders of the same two cleaning steps against the clearness and no-clog criteria, then choose one, the compare-solutions reasoning at the heart of this standard.

All materials for 3-5-ETS1-2 →

Download Word file

This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-07-23.

Objectives

Students will define clean water for Willowmere using a clearness criterion and a no-clog constraint.
Students will compare two orders of the same two cleaning steps and choose the order that works better.
Students will explain why letting muddy water settle before filtering helps the filter last longer.

Vocabulary

Key words: settle, filter, sediment, criteria, constraint

Teacher overview

The fictional town of Willowmere draws its water from the Slate River, and after a storm that river runs thick and brown with mud. This lesson asks students to act as junior engineers who plan the order of two cleaning steps, letting the mud settle and pouring the water through a filter, so the water comes out clear without ruining the filter. The demonstration is deliberately run in the weaker order first, because many groups assume the two steps work equally well either way, and watching a filter clog on thick mud gives them something concrete to weigh their own order against.

Procedure

Hook (5 min): Hold up a jar of the muddy river water and ask the class, "Would you want to drink this? What would we have to do to it first?" Record the steps students suggest on chart paper in the order they say them.

Direct instruction and demonstration (15 min): Introduce the two cleaning steps on process-order cards: Settle (let the water sit still so heavy mud sinks to the bottom) and Filter (pour the water through a coffee filter to catch smaller bits). State the success criterion with the class: the water should come out clear. Add the constraint written on a card: the filter must not clog before the job is done. Demonstrate the wrong order first by pouring thick muddy water straight through a filter so students watch it clog and slow to a drip. For safety, mix the sample from clean garden soil rather than from stream or pond material, keep the jars away from faces, tell students that none of the water in this lesson is for drinking, even after it looks clear, and have everyone wash their hands afterward.

Guided practice (15 min): In small groups, students arrange the two cards into the order they think works best, then write how their order meets the clearness criterion and respects the no-clog constraint. Have each group compare their chosen order with a second order (the reverse) and mark which one they predict will keep the filter working longer.

Closure / exit ticket (10 min): For a formative check, ask each student to answer one prompt on an index card: "Should Willowmere settle the water first or filter it first, and why?" Collect the cards and scan for the key idea that settling first removes heavy mud so the filter lasts longer; reteach briefly to any group whose answers miss it.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key

These are the expected answers to the lesson's three questions: the success criterion (direct instruction), the better order (guided practice and exit ticket), and why the other order fails.

Answer: The water should come out clear.
This is the success criterion the class should state. Accept any wording that describes clear or clean water as the goal both process orders are measured against.
Answer: Settle first, then filter.
Letting the water settle first drops the heavy mud to the bottom, so much less mud reaches the filter. Accept an answer that names settling before filtering and connects it to keeping the filter from clogging.
Answer: Filtering thick muddy water first clogs the filter quickly, so it can no longer let water through.
This is the reasoning behind the no-clog constraint. Accept any answer that connects unsettled mud to a filter that clogs, slows, or stops working before the job is done.

Differentiation

Support

Give students the two process-order cards already labeled with a small picture (mud sinking in a jar for Settle, water dripping through paper for Filter) and a sentence frame: "I would ___ first because ___." Let them arrange the physical cards before writing.

Extension

Ask students to add a third step of their own to Willowmere's plan, such as adding a screen to catch leaves and sticks before settling, and to explain where in the order it should go and why. Have them defend the new order against the same two criteria.

ELL supports

Pre-teach "settle," "filter," "sediment," "criteria," and "constraint" with the live jar demonstration and matching gestures (hands sinking down for settle, fingers straining for filter). Allow the exit-ticket answer to be drawn as a two-box sequence with labels rather than written in full sentences.