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Two Filters, One Intake Pipe

Students compare two engineering designs using quantitative test data and argue why a two-stage filter outperforms a single fine screen.

Student Name: ______________________

Grade Band: Grades 6-8

Words

  • stage. one step or layer in a multi-step engineering process Example: The coarse gravel bed is the first stage of the new filter.
  • coarse. made of larger, rougher pieces such as pebbles or gravel Example: Coarse gravel traps leaves and large sand before they reach the wire mesh.
  • capacity. the amount a system can hold or process before clogging Example: Adding a gravel pre-filter quadrupled the run-time capacity of the pipe.
  • duration. how long something continues to work before stopping Example: Amina measured the duration of steady flow in minutes.
  • tradeoff. a balance where gaining one advantage requires accepting a small cost Example: The tradeoff of the two-stage box is five extra minutes of rinsing.
  • evidence. measured numbers or observations that support an engineering claim Example: The ninety-minute run time is evidence that the two-stage design works.

Speaking plan

Argue for installing Design B on Basin Three by contrasting the 20-minute and 90-minute test data, explaining the two-stage mechanism, and addressing the rinse-time tradeoff.

  1. State the recommendation for Design B.
  2. Contrast the 20-minute and 90-minute durations and explain particle-size staging.
  3. Address why an 8-minute rinse every 90 minutes still saves labor.

Writing plan

Write an engineering argument for Mateo recommending Design B over Design A. Cite the quantitative run-time comparison, explain how staged filtration prevents rapid blinding, and address the maintenance tradeoff.

  1. Contrast Design A (20 minutes) with Design B (90 minutes).
  2. Explain how the coarse gravel pre-filter protects the 100-micron mesh.
  3. Use causal and comparative connectors (whereas, because, therefore).

Guided frames

  • Mateo, we should install the two-stage filter on Basin Three because ___.
  • In the bench test, the single screen clogged in 20 minutes, whereas the two-stage filter ___.
  • The coarse gravel helps because ___.

Drafting & Evidence Sketch Space