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Lesson plan Grade 8 English Language Arts

Sentence Combining for the Kilnwick Slow Sand Filter

A grade 8 ELA lesson in which students combine choppy kernel sentences about a fictional town's slow sand filter into clear explanatory prose.

Objectives

  1. Students will combine kernel sentences using subordinate clauses, appositives, and participial phrases.
  2. Students will explain in ordered prose how a slow sand filter cleans water.
  3. Students will judge which of two combined versions states a process more clearly and defend the choice.

Vocabulary

Slow sand filter
A slow sand filter cleans water by letting it trickle very slowly through a deep bed of sand, where a thin layer of living microorganisms on top helps trap and break down impurities. It is one of the oldest and simplest ways to treat water, still used today in some small systems.

Also: schmutzdecke, subordinate clause, appositive, participial phrase, ripening

Teacher overview

Eighth graders are often told to vary their sentences without being shown what varied syntax actually does for a reader. This lesson gives them a process worth explaining, the workings of a slow sand filter in a fictional town, and asks them to combine short kernel sentences into prose that keeps every fact and makes the relationships between the facts visible. Two misconceptions shape the plan. The first is technical: students assume a sand filter works like a kitchen strainer, catching particles in the gaps between grains, when in a slow sand filter most of the cleaning is done by a living layer of algae and bacteria that grows on the surface. The second is about writing: many students combine sentences by chaining them with "and," which makes a sentence longer without making the relationship between its parts any clearer.

Procedure

Hook (5 min): Project two versions of the same three facts, one written as three short sentences and one combined with a "because" clause. Ask students which version tells them why the sand is fine, and take three responses. Do not name the grammar terms yet.

Direct instruction (10 min): Introduce three moves for combining sentences: the subordinate clause, which shows cause or time; the appositive, which folds a definition into a noun phrase; and the participial phrase, which attaches an action to the subject already in the sentence. Model each move once on the board using facts about the fictional plant, thinking aloud about which relationship each move makes clear. Keep all three models visible for the rest of the period.

Guided practice (12 min): Work through handout item 1 as a class, writing two acceptable versions and one version that loses information. Students then complete items 2 and 3 in pairs while you circulate. Ask two pairs to read a sentence aloud and name the move they used.

Independent practice (15 min): Students complete handout items 4 through 8 on their own. Item 7 asks them to compare two student versions and defend a choice, and item 8 asks them to write original sentences for a plant tour brochure.

Share and revise (5 min): Three volunteers read their item 8 sentences. The class names the move used in each and suggests one revision. Writers make the revision on their own page before turning it in.

Exit ticket (3 min): On an index card, students combine these two sentences using a subordinate clause: "The plant keeps two filter beds. One bed can be cleaned without shutting off the town's water." Collect the cards. If fewer than three-quarters of the class produces a clause beginning with a subordinating conjunction, reteach the move at the start of the next period.

Sentence Combining for the Kilnwick Slow Sand Filter — Grade 8 English Language Arts
Name: ____________________________ Date: ______________

Student Handout

Kilnwick is a fictional town of about 2,400 people. Its water plant draws from Bitternut Creek and treats the water in a slow sand filter. Creek water first sits in a settling basin, where the heavy grit drops out. It then moves down through a bed of fine sand about three feet deep. Within a week or two, a thin living layer of algae and bacteria grows on the sand surface. Operators call that layer the schmutzdecke, and it does most of the cleaning. When the layer grows thick enough to slow the flow, the crew drains the bed and scrapes off the top inch of sand. The plant runs two beds so that one can ripen while the other filters.

For items 1 through 5, combine the sentences into clear prose. Keep every fact. Use the move named in parentheses.

  1. (Use a subordinate clause beginning with "because.") The sand in the bed is very fine. Water moves down through it slowly.
  2. (Use an appositive.) Priya Rasheed is the plant's lead operator. She measures the flow through each bed every morning.
  3. (Use a participial phrase.) The creek water sits in a settling basin first. It drops most of its grit there. The sand bed stays clean longer.
  4. (Use a subordinate clause beginning with "while" or "after.") A thin living layer grows on top of the sand. Operators call the layer the schmutzdecke. The layer does most of the cleaning.
  5. (Combine into exactly two sentences.) The flow slows down. The layer has grown thick. The crew drains the bed. They scrape off the top inch of sand. The bed goes back into service. It needs about two weeks before it cleans well again.
  6. Rewrite this run-on in no more than two sentences so that the relationship between the ideas is clear: "The plant has two beds and one bed is always ripening and the other bed is filtering and that way the town never runs out of treated water."
  7. Two students combined the same facts. Which version states the process more clearly, and why?
    Version 1: "The layer on top of the sand does most of the cleaning, and it is made of algae and bacteria, and it takes about two weeks to grow." Version 2: "Because the living layer of algae and bacteria on top of the sand does most of the cleaning, a freshly scraped bed needs about two weeks before it filters well again."
  8. Write two sentences for a plant tour brochure explaining why the fictional plant keeps a second bed. Use one subordinate clause and one precise verb such as ripen, scrape, settle, or filter.

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: Because the sand in the bed is very fine, water moves down through it slowly.
    Accept any version in which the "because" clause carries the grain size and the main clause carries the slow movement. Do not accept a version that drops either fact.
  2. Answer: Priya Rasheed, the plant's lead operator, measures the flow through each bed every morning. The appositive must sit between commas and must define the subject rather than add a new action.
  3. Answer: Sitting in a settling basin first, the creek water drops most of its grit and leaves the sand bed cleaner longer. Accept any version that opens with a participial phrase and keeps all three facts.
  4. Answer: After a thin living layer called the schmutzdecke grows on top of the sand, that layer does most of the cleaning. Accept versions using "while" if the time relationship stays accurate, and accept the term folded in as an appositive.
  5. Answer: When the flow slows because the layer has grown thick, the crew drains the bed and scrapes off the top inch of sand. The bed then goes back into service, though it needs about two weeks before it cleans well again. Two sentences are required, and no fact may be lost.
  6. Answer: The plant has two beds, so one is always ripening while the other filters. That arrangement keeps treated water flowing to the town. Accept any two-sentence version that replaces the chain of "and" with a cause or contrast relationship.
  7. Answer: Version 2. It uses a subordinate clause to show that the cleaning done by the living layer is the reason a scraped bed takes time to recover, while Version 1 lists the same three facts as equal items and leaves the reader to guess how they connect.
  8. Answer: Accept any two sentences that are accurate, contain at least one subordinate clause, and use a precise verb such as "ripen," "scrape," "settle," or "filter." A full-credit response explains that one bed can be cleaned while the other keeps producing water.

Differentiation

Support

Give these students a version of the handout in which items 1 through 3 already show the first three words of an acceptable answer, and provide a bank of subordinating conjunctions with a one-word gloss for each. Reduce the required items to 1, 2, 4, and 8.

Extension

Ask students to rewrite item 5 twice more, once for a reader who has never seen a filter and once for a state inspector, then to write a short paragraph naming the choices that changed between the two versions and explaining why.

ELL supports

Pre-teach "settle," "scrape," "ripen," and "layer" with a labeled cross-section drawing of the fictional filter bed showing the living layer on top of the sand. Provide each combining move as a sentence frame, and allow items 1 through 4 to be completed orally with a partner before writing.

Extensions

Students choose another process they know well, such as sanding a board or proofing bread dough, write five kernel sentences about it, and trade with a partner who must combine them using all three moves practiced in the lesson.