Classroom activity Grade 5 Engineering & Design
Pennick Creek Intake Screen: A Grade 5 Mesh Choice Activity
Teams pour a model of leafy creek water through three mesh screens, time each one, and choose the mesh that meets a fictional town's two intake rules at once.
Objectives
- Students will state a screen design problem as two success rules and one limit.
- Students will run the same pour test on three meshes while holding other conditions steady.
- Students will choose one mesh and name what their choice gives up.
Vocabulary
Key words: intake, screen, mesh, debris, trade-off
Teacher overview
This is a 50-minute hands-on test for teams of three or four. Every water plant that draws from a river or lake begins with a screen at the intake, and the screen has two jobs that pull against each other: it must block the leaves, sticks, and grit that would damage pumps downstream, and it must let water through fast enough to keep the plant supplied. Teams working for the fictional town of Pennick test three meshes, from coarse to very fine, by pouring the same leafy water through each one and timing it. Because each team measures its own pour, there is no single correct result, and the point of the activity is the choice a team defends rather than a number it reports.
The misconception to name before students start is that a finer screen is simply a better screen. Fifth graders often reach for the cheesecloth, reasoning that catching more is always better. What they discover is that the finest mesh clogs partway through the pour and the water slows to a trickle, which at a real plant means the town runs short. Say this plainly at the debrief: a screen fine enough to hold back every particle also slows the water below what the plant needs, so the screen a plant installs is the one that holds back enough debris while still passing enough water. A second thing worth watching is the pour itself. Teams that raise the cup higher on the third trial get a faster time that has nothing to do with the mesh, so step 7 exists to hold that steady.
Activity Directions
- Before class, cut the bottoms out of three clear cups per team and cut mesh squares large enough to cover a cup mouth with an overhang. Mix the debris water in a pitcher: plain tap water with a handful of torn paper pieces and a spoonful of dry coffee grounds stirred in. Stir again before every pour, since the grit settles fast.
- Set out one tray per team with the three cups, the three mesh squares, rubber bands, a catching jar, a measuring cup, and a timer. Name the meshes aloud: coarse is the needlepoint canvas, medium is the window screen, and fine is the cheesecloth.
- Give teams the scenario. Pennick draws its drinking water from Pennick Creek, and the intake needs one screen. Write the two rules on the board and have each team copy them onto the recording sheet: the screen must keep leaves and grit out of the pipe, and it must pass one measured cup of water in 20 seconds or less. Add the limit: the town will install one screen, so teams cannot stack two.
- Teams band the coarse mesh over the mouth of the first cup, hold it over the catching jar, and have one member ready with the timer.
- The pourer stirs the pitcher, measures exactly one cup of debris water, and pours it steadily through the mesh while the timer runs. Stop the timer when the dripping stops. Record the time and look in the jar.
- Teams count or estimate how much debris came through into the jar and record it as none, a little, or a lot. They also note whether the mesh clogged before the pour finished.
- Repeat steps 4 through 6 for the medium mesh and then the fine mesh. Remind teams to keep three things the same every time: one measured cup of water, a fresh stir of the pitcher, and the same pouring height, which they should mark on the side of the tray.
- Stop the testing once all three meshes have been run, which usually takes about 20 minutes. Teams complete the handout questions.
- Debrief as a class. Ask two teams that chose different meshes to defend their choices using their own recorded times and debris notes, then ask the class what a town would have to add downstream if it installed the coarse mesh.
Student Handout
Fill in the table as you test. Then answer the questions in sentences.
| Mesh | Time for one cup | Debris in the jar | Did it clog? |
|---|---|---|---|
| Coarse (needlepoint canvas) | |||
| Medium (window screen) | |||
| Fine (cheesecloth) |
- Which mesh let the water through fastest, and which let the most debris through with it?
- Which mesh blocked the most debris, and what happened to its pouring time?
- Pennick will install one screen. Which mesh do you choose, and which of the town's two rules does your choice meet best?
- Every choice gives something up. Name one thing your chosen mesh does not do well, and describe one change you would make to the screen to fix 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
- Answer: Results vary by team.
Accept any answer in which the mesh named as fastest matches the shortest time in that team's own table. The coarse needlepoint canvas is the usual answer, and it normally lets grit and small paper pieces through. - Answer: Results vary by team.
Accept any answer naming the fine cheesecloth, or whichever mesh that team recorded as blocking the most, paired with a note that its pour took longer or stopped early. Most teams find the fine mesh clogs partway through. - Answer: The medium window screen, or the coarse mesh with supporting data.
Accept either choice when the team points to its own recorded time and debris note. The medium window screen is the strongest answer, since it usually passes the cup within the time rule while still holding back the paper pieces. Do not accept a choice defended only by the words "it is cleanest," with no reference to the time rule. - Answer: Answers vary; accept any trade-off the team names honestly.
Common answers are that the medium mesh lets fine grit through, or that the coarse mesh passes leaves that would reach the pump. Reasonable changes include adding a second treatment step after the screen, sloping or curving the screen so debris slides off, or making the screen larger in area so it passes the same water more slowly through each opening.
Differentiation
Support
Assign these students the roles of timer and recorder, and give them a recording sheet with the three mesh names already printed and the debris column offered as three pictures to circle rather than words to write. Run their first trial with the teacher pouring, so the team sees the pouring height held steady before they take it over.
Extension
Ask these teams to design and test a fourth screen of their own by layering or folding a mesh, or by cutting the cheesecloth to cover only half the opening, then to predict before pouring where their design will land on time and debris. They should explain why a real intake screen is usually much larger than the pipe it protects.
ELL supports
Pre-teach "mesh," "intake," "debris," and "clog" by holding each material up and passing it around while saying the word. Post the two rules as short pictures on the board: a leaf with a line through it, and a clock. Provide this frame for question 3: "We choose the ___ mesh because it ___ ." Allow spoken answers recorded by a partner.
Extensions
Many utilities post a photograph of the intake structure that begins their treatment process, and finding one shows students how large a real screen is compared with the pipe behind it. If the class keeps an aquarium, comparing its filter intake screen with the meshes tested here gives a second, smaller example of the same design problem.