Classroom activity Grade 5 Engineering & Design

Marsh Hollow Settling Basin: A Grade 5 Fair-Test Activity

A grade 5 hands-on activity where teams compare still and stirred jars of muddy water to see how a settling basin lets heavy dirt sink out at a treatment plant.

Grade: Grade 5
Subject: Engineering & Design
Material: Classroom activity
Time: 45 min
Prep: Moderate prep
Materials: 2 clear jars or clear cups with lids per team, Muddy water mix (soil stirred into water), about 2 cups per team, Spoon or stir stick per team, Timer or classroom clock, A page of printed text to hold behind the jar as a clarity check, Safety glasses, one per student

Standards

3-5-ETS1-3 NGSS

Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

How this material aligns: Teams control the jar, the muddy water, and the amount, changing only whether the water is stirred or left still, then read the clearer top layer, the controlled fair test this standard requires.

All materials for 3-5-ETS1-3 →

5-ESS3-1 NGSS

Obtain and combine information about ways individual communities use science ideas to protect the Earth's resources and environment.

How this material aligns: The activity and debrief connect settling to how a community's treatment plant removes heavy dirt before cleaning water further, the human-use-of-science idea this standard describes.

All materials for 5-ESS3-1 →

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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 design a fair test that compares still water and stirred water for how well dirt settles out.
Students will observe and describe how heavy particles sink to the bottom over time.
Students will explain why settling is an early cleaning step at a treatment plant.

Vocabulary

Key words: settling, basin, sediment, particle, still

Teacher overview

This is a small-group activity for teams of three or four. The fictional Marsh Hollow plant cleans water that arrives full of dirt, and its very first step is a settling basin, a big, calm tank where heavy dirt is given time to sink to the bottom before the water moves on. Teams model that step with two jars of muddy water: one they leave perfectly still, one they keep gently stirred. By comparing how clear the top of each jar becomes, students see that a settling basin works because the water is held calm long enough for the dirt to sink. The results depend on what each team observes, so there is no single right number; the point is a careful, fair comparison.

Activity Directions

Before class, mix a batch of muddy water by stirring soil into water until it looks like chocolate milk. Give each team about 2 cups. Have every student put on safety glasses before handling the jars, and remind students not to taste or drink the muddy water and to wash their hands afterward.
Explain the settling basin: at a real plant, dirty water sits in a large, calm tank so heavy dirt sinks before the water is cleaned further. Tell teams they will test whether still water or stirred water settles better.
Have each team fill two clear jars with the same amount of muddy water, poured from the same batch, so the only difference will be how the water is treated. Label one jar "Still" and one jar "Stirred."
As a class, name what is kept the same (the jar, the amount, the muddy-water batch) and what is changed (still versus stirred). This is what makes the test fair.
Teams set the "Still" jar down and do not touch it. One team member keeps the "Stirred" jar in slow, steady motion with a spoon, or by gently swirling, the whole time.
At 2 minutes, 5 minutes, and 10 minutes, teams hold the printed-text page behind each jar's top few centimeters and decide which jar's top water is clearer. They record what they see on the handout each time.
End the activity at 10 minutes. Have teams look down into the "Still" jar and describe the layer of settled dirt on the bottom.
Debrief with the whole class using the two questions on the handout. Call on several teams so different observations are shared.

Marsh Hollow Settling Basin: A Grade 5 Fair-Test Activity — Grade 5 Engineering & Design

Name: ____________________________ Date: ______________

Student Handout

Answer as you go. Short phrases and labeled sketches are fine.

At each time check (2, 5, and 10 minutes), which jar's top water looked clearer, "Still" or "Stirred"? Record your choice each time.
Describe the bottom of the "Still" jar at 10 minutes. What do you see there?
Debrief question: Why does a settling basin at a plant keep the water calm instead of moving?
Debrief question: Settling removes heavy dirt, but the water is still not safe to drink. Why does a plant need more steps after settling?

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

Answer Key

Answer: In almost every team, the "Still" jar's top water becomes clearer at each check, and the gap grows by the 10-minute reading. Accept the team's recorded choices as long as they match what they observed.
Answer: Students should describe a layer of settled dirt, or sediment, resting on the bottom of the still jar, with clearer water above it. Accept any answer that names the sunken dirt layer.
Answer: Calm water lets heavy dirt particles sink straight to the bottom. Moving or stirred water keeps lifting the dirt back up, so it never settles, which is why a real basin is kept still.
Answer: Settling only removes the heavy dirt that will sink. It does not remove germs or the tiny particles that stay floating, so the plant still needs later steps, such as filtering and adding a disinfectant, before the water is safe to drink.

Differentiation

Support

Pre-fill both jars for these teams so they begin at the observing step. Give a simple recording sheet with just the three time checks and a "clearer jar" circle to mark, and pair a student who records with a student who watches the clock.

Extension

Have these teams add a third jar and test a new idea of their own, such as whether warm muddy water settles faster than cold, while keeping everything else the same. Ask them to write which variable they changed and what they predict before they test.

ELL supports

Pre-teach "settle," "still," "sediment," and "particle" by pointing to the muddy water and the sinking dirt as you say each word. Provide picture cards showing a stirred jar and a still jar, and allow students to record clearer-jar choices by circling a picture instead of writing.

Extensions

If a nearby drinking-water or wastewater plant offers tours, ask whether students can see the settling or sedimentation basins and how long the water rests there. Back in class, students can compare the plant's calm basin to their own "Still" jar and describe what is the same about how each one works.