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Lesson plan Grade 7 English Language Arts

How Delford Cleans Its River Water: An Explanatory Writing Lesson

A 50-minute grade 7 lesson where students read how a fictional plant cleans river water, then write an explanatory paragraph using cause-and-effect structure.

Objectives

  1. Students will explain the four steps a treatment plant uses to clean river water, in the correct order.
  2. Students will write an explanatory paragraph that uses sequence and cause-and-effect transitions.

Vocabulary

Coagulation
Coagulation is the first cleaning step at a drinking water plant. Operators quickly mix in a chemical that makes tiny bits of dirt stop pushing each other away so they can start sticking together.
Sedimentation
Sedimentation is the step where water sits almost still in a big basin so the heavy clumps of dirt can sink to the bottom. The cleaner water on top then moves on to the filters.
Filtration
Filtration is the step where water passes through layers of sand, gravel, or other materials that trap the small particles still left in it. It works like a very fine strainer.
Disinfection
Disinfection is the step that kills or disables germs in water so it is safe to drink. Water plants usually disinfect with chlorine, ultraviolet light, or ozone.

Also: explanatory

Teacher overview

The fictional town of Delford draws its drinking water from a river, so the water arrives at the plant cloudy and full of tiny particles. This lesson gives students a short informational text about the four steps the plant uses to clean that water, then asks them to turn what they read into an explanatory paragraph. Informative writing at grade 7 is judged on structure, not opinion, so the lesson keeps the focus on ordering ideas clearly and connecting each step to its effect. A common trouble spot is that students list the steps without explaining why the order matters; the modeling step addresses this directly.

Procedure

Hook (5 min): Hold up a clear cup of tap water and ask students to describe what the same water might have looked like when it was still in the river. Record a few responses about color, smell, and floating particles. Tell students that a treatment plant changes river water into the clear water in the cup, and that today they will explain how.

Read the source text (10 min): Distribute the student handout. Students read the plant-tour text once on their own, then reread it with a highlighter, marking the name of each treatment step and one detail about what that step does. Circulate and confirm students can locate all four steps in order.

Model the paragraph (10 min): On the board, think aloud as you write a topic sentence and the first two sentences of an explanatory paragraph about Delford's plant. Show how transition words such as "first," "next," "because," and "as a result" connect one step to the next. Name the move explicitly: an explanatory paragraph tells the reader not only what happens but why each step depends on the one before it.

Guided and independent writing (15 min): Students complete questions 1 through 4 on the handout to gather their ideas, then draft the full explanatory paragraph in question 5. Remind them to use at least three transition words and to explain the purpose of each step, not just name it.

Peer check and revise (7 min): In pairs, students trade paragraphs and check for two things: are the four steps in the correct order, and does each step include a reason or effect? Writers revise one sentence based on their partner's feedback.

Exit ticket (3 min): Students answer one question on an index card: "Why does the plant let water sit still in a settling tank before it reaches the filters?" Collect and scan for the idea that settling lets heavy clumps sink first, so the filters are not overwhelmed. If more than a third of the class misses this, reteach the sedimentation-to-filtration link before the next session.

How Delford Cleans Its River Water: An Explanatory Writing Lesson — Grade 7 English Language Arts
Name: ____________________________ Date: ______________

Student Handout

A tour of the Delford plant. River water enters the Delford treatment plant looking cloudy because it carries silt, clay, and other small bits. The plant cleans it in four steps. First, workers add a chemical that makes the tiny particles stick together into larger clumps. This step is called coagulation. Next, the clumped water flows into a large, calm tank and slows down. The heavy clumps sink to the bottom, which is called sedimentation. After that, the water passes down through layers of sand and gravel that trap the smaller particles still floating in it. This step is filtration. Finally, the plant adds a small amount of a disinfectant to kill germs so the water stays safe on its way to homes. This last step is disinfection. The steps must happen in this order, because each one prepares the water for the next.

  1. List the four treatment steps in the order the plant uses them.
  2. In your own words, explain what coagulation does to the tiny particles.
  3. The text says the steps must happen in order. Using cause and effect, explain what would go wrong if the water reached the filters before it passed through the settling tank.
  4. Write a topic sentence for a paragraph that explains how Delford cleans its river water.
  5. Using your answers above, write an explanatory paragraph of five to seven sentences that names all four steps in order and explains the purpose of each. Use at least three transition words.

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

Answer Key
  1. Answer: Coagulation, sedimentation, filtration, disinfection. The text presents the steps in this exact order, and students should reproduce it.
  2. Answer: Coagulation adds a chemical that makes the small particles stick together into larger clumps. Accept any wording that captures particles joining into bigger pieces.
  3. Answer: The filters would clog quickly or let too many particles through, because the heavy clumps would not have had a chance to sink first. Sedimentation removes the largest material so the filters only handle the smaller particles that remain.
  4. Answer: Answers will vary. A strong topic sentence names the subject and previews the idea of ordered steps, such as: "The Delford plant cleans river water through four steps that must happen in order."
  5. Answer: Answers will vary. A proficient paragraph opens with a topic sentence, names coagulation, sedimentation, filtration, and disinfection in order, gives the purpose of each, uses at least three transitions such as "first," "next," "because," and "as a result," and closes with a sentence about the water being safe to deliver.

Differentiation

Support

Provide a version of the handout with the four step names already listed and a sentence frame for each ("The ___ step ___ because ___."). Let these students complete the frames instead of writing the paragraph from a blank page, then combine the frames into a paragraph.

Extension

Ask students to add one sentence to their paragraph explaining why river water usually needs more treatment than water pumped from a deep well, using the idea that river water is exposed to more dirt and runoff at the surface.

ELL supports

Pre-teach the four vocabulary terms with a simple labeled diagram showing water moving from a river through four tanks to a house. Allow students to say each step aloud in order before writing, and provide the transition words on a printed strip they can point to and copy.

Extensions

Invite a local water utility to share, by email or a short visit, how many treatment steps their own plant uses and whether their source is a river, a lake, or wells. Students then revise their paragraphs to compare Delford's fictional plant with the real local process, which turns the writing task into an authentic piece of community reporting.