Worksheet Grade 6 English Language Arts
Summarizing the Thistlebank Digester Article: A Grade 6 Worksheet
Students judge three candidate summaries of an article about a fictional plant's methane digester, then write their own summary free of opinion and stray detail.
Objectives
- Students will identify the central idea of a short informational article.
- Students will explain why a too-broad summary and a retelling both fail as summaries.
- Students will write a three-sentence summary that excludes opinion and minor detail.
Vocabulary
Key words: central idea, summary, detail, opinion, digester, methane
Teacher overview
Sixth graders can usually tell a summary from a retelling once they see the two side by side, yet when asked to write one on their own, many produce a shortened retelling instead. This worksheet puts three candidate summaries of the same short article in front of students and makes them argue about each one before writing their own. The article describes a sealed tank at a fictional treatment plant where bacteria turn leftover solids into a burnable gas. The misconception to name first is that a summary is simply a shorter version of the text: a summary keeps the central idea and drops the rest, so the sentences a student deletes matter as much as the ones kept.
Student Worksheet
Read the article. Thistlebank and its treatment plant are fictional, invented for this worksheet.
Power from a Sealed Tank
The Thistlebank Water Resource Recovery Facility cleans the wastewater from about nine thousand homes. Cleaning the water leaves solids behind. Years ago the plant trucked those solids away. Now it feeds them into a sealed steel tank called a digester.
Nothing inside the digester breathes air. The bacteria that live there work without oxygen, and they need about three weeks to break the solids down. As they work, they give off a gas that is mostly methane, which is the same gas that burns on a kitchen stove.
The plant does not waste that gas. It pipes the gas to an engine that turns a generator, and the generator makes electricity for the plant itself. The engine also gives off heat, and the plant pumps that heat back into the digester. The bacteria are fussy about temperature and stop working well if the tank cools down.
In a normal month the digester gas covers close to half of the electricity the plant uses. Any town with a plant this size would be foolish not to try it. What remains in the tank after three weeks is a stable material that no longer smells, and the plant sends it to farms nearby.
Operators check the gas readings every day. A sudden drop usually means the bacteria are in trouble, either because the tank has cooled or because the plant fed them too much too fast.
In one sentence, state the central idea of the article.
Which of the three summaries below is the best summary of the article?
A. Treatment plants across the country are finding new ways to save money and protect the environment, and Thistlebank is one example of this trend.
B. First the plant cleans the water. Then solids are left. Then the solids go into a tank. Then bacteria work for three weeks. Then gas comes out. Then an engine burns it.
C. At the Thistlebank plant, bacteria in a sealed tank break down leftover solids and give off methane. The plant burns that gas to make much of its own electricity and to keep the tank warm. The solids that remain are stable enough to send to farms.
Summary A is not a good summary of this article. Explain in one sentence what is wrong with it.
Summary B is not a good summary of this article. Explain in one sentence what is wrong with it.
Copy the sentence from the article that best supports the idea that the digester lowers what the plant spends on electricity.
What does the word "digester" mean as it is used in this article?
The article says the bacteria "work without oxygen." What does that phrase tell you about where these bacteria can live?
One sentence in the article states an opinion rather than a fact. Copy that sentence.
Operators check the gas readings every day. Using the article, explain in one or two sentences why a sudden drop in the gas reading would worry them.
Write your own summary of the article in exactly three sentences. Include the central idea and the two most important supporting ideas, and leave out your own opinion.
A classmate writes this sentence: "The plant burns the gas from the tank, so it buys less electricity." Is that sentence a summary of the whole article or one supporting detail? Explain your answer in one sentence.
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: The Thistlebank plant uses a sealed digester tank where bacteria turn leftover solids into methane gas, which the plant burns to power and heat itself. Accept any sentence that names both the digester and the useful gas it produces.
- Answer: C. It states the central idea first, keeps only the two supporting ideas that matter most, and adds no opinion.
- Answer: Summary A is too broad. It could describe almost any plant anywhere and never mentions the digester, the gas, or the electricity, which are what this article is about.
- Answer: Summary B is a retelling rather than a summary. It lists the steps in order without ever saying why the plant does any of it, so a reader learns the sequence and misses the point.
- Answer: "In a normal month the digester gas covers close to half of the electricity the plant uses." That sentence gives the size of the saving. The paragraph 3 sentence about the generator shows the plant makes its own electricity but not how much it replaces, so accept it for partial credit.
- Answer: A large sealed tank where bacteria break down solids without air. The article defines it in place, calling it "a sealed steel tank" that the plant feeds solids into.
- Answer: They can live in places with no air, such as the inside of a closed tank, and they do not need oxygen the way people and most animals do. Accept any answer showing the bacteria survive in an airless space.
- Answer: "Any town with a plant this size would be foolish not to try it." The word "foolish" is a judgment about other towns, and nothing in the article can prove or disprove it.
- Answer: Because the gas reading tells them how the bacteria are doing. The article says a sudden drop usually means the tank has cooled or the bacteria were fed too much too fast, so a falling reading is an early warning that the digester is failing.
- Answer: Accept any three-sentence summary that names the digester and the bacteria, states that the gas is burned for the plant's electricity and heat, and stays free of opinion. A full-credit response resembles Summary C. Deduct if the student includes the number of homes, the trucking of solids in past years, or any judgment about whether the plant made a good choice.
- Answer: It is one supporting detail. The sentence covers only the gas and the electricity and leaves out the bacteria, the tank, and what happens to the solids afterward, so it cannot stand for the whole article.
Differentiation
Support
Read the article aloud once while students follow along, then reread paragraph three only, since that paragraph carries the central idea. Give these students the article with each paragraph's topic already written in the margin, and reduce item 10 to two sentences. For items 3 and 4, provide the labels "too broad" and "retells the steps" and ask students to match a label to a summary before explaining.
Extension
Ask these students to write a one-sentence summary, then a five-sentence summary, of the same article, and to write two sentences explaining what they had to give up to get down to one sentence. A second option is to rewrite Summary B so that it becomes a genuine summary while keeping the same information it currently reports.
ELL supports
Pre-teach "solids," "sealed," "bacteria," "gas," and "generator" with a simple flow sketch showing the tank, the pipe, the engine, and the heat returning to the tank. Provide the three candidate summaries with the key difference in each one underlined. Allow students to answer items 6 and 7 with a drawing plus a short phrase, and offer the frame "This summary is not good because it ___" for items 3 and 4.
Extensions
Have students find a short public page from a real utility describing what it does with the solids left after treatment, then write two sentences naming what that utility does differently from Thistlebank and one sentence about why the difference might exist.