Analyze how the sections of a technical text are organized and why the author explains, describes or discusses

Learning goal: Analyze the structure an author uses to organize a science or technical text, including how each major section contributes to the whole and to an understanding of the topic, and analyze the author's purpose in providing an explanation, describing a procedure, or discussing an experiment.

Original technical text — Why a Compost Pile Gets Hot, and How to Keep It That Way. Written for this lesson. The temperature readings are hypothetical.

Background: where the heat comes from. A compost pile is a heap of plant material, such as leaves, grass clippings and vegetable scraps, that is being broken down by bacteria and fungi. These decomposers feed on the material and, like all living things that respire, release energy as they do. In a small heap the energy escapes to the air as fast as it is produced, and the pile stays close to the temperature of its surroundings. In a heap about a cubic meter or larger, the middle is insulated by the outside, heat builds up, and the center can climb well above 50 degrees Celsius. The decomposers need three things: a food mix that is neither all carbon-rich dry material nor all nitrogen-rich fresh material, moisture, and oxygen. A pile that is too dry stops; a pile that is too wet or too tightly packed runs out of oxygen, and different microbes take over that produce sour or rotten smells instead of heat.

Procedure: building a pile that heats. (1) Choose a shaded spot on bare soil about 1 m square. (2) Collect two kinds of material: browns, which are dry and carbon-rich (fallen leaves, straw, shredded paper), and greens, which are moist and nitrogen-rich (grass clippings, fruit and vegetable scraps, coffee grounds). Do not use meat, dairy or oily food, which attract animals. (3) Build the pile in layers about 10 cm thick, alternating two parts browns with one part greens by volume, and sprinkle each layer with water until the material feels like a wrung-out sponge. (4) Continue until the pile is about 1 m high. (5) Push a long-stemmed compost thermometer into the center and record the temperature at the same time each day. (6) When the center temperature falls by 5 degrees or more from its peak, turn the pile with a fork, moving the outside material to the middle, and water any dry layers. (7) Wash hands after handling the pile.

Results: one pile's first month. A class built a pile following the procedure on a day when the air was 18 degrees Celsius. The center read 18 degrees on day 0, 41 on day 2, 58 on day 4, and 62 on day 7. It then fell to 55 by day 10, so the class turned the pile that afternoon. The center read 60 on day 12, 45 on day 18 and 32 on day 25. Step 6 called for a second turn once the center fell 5 degrees below the new peak of 60, which had happened by day 18, but the class did not turn the pile again, so the readings after day 12 come from a pile left unturned. The class expected the rise, because the background section predicts that a pile of this size traps the decomposers' heat. They had not expected the fall after day 7, and they concluded, after turning restored the heat, that the decomposers in the center had used up the oxygen or the easiest food, and that turning supplied both. They could not tell which of the two mattered more, because turning changes both at once. A second pile built the same way but only 40 cm high never rose above 24 degrees.

Troubleshooting. A pile that smells of ammonia has too many greens; add browns and turn it. A pile that smells sour or rotten is too wet or too packed; turn it and add dry browns. A newly built pile that never heats is usually too small, too dry, or too rich in browns; combine piles, water it, or add greens. A pile that was hot and has cooled for good may simply be finished: if the material is dark, crumbly and smells like soil, it needs nothing added.

Analyzing structure: what the sections are and how they are ordered. Structure is the plan the author used to organize the text: the major sections, their order, and the smaller devices inside them, such as numbered steps, a sequence of dated readings, and a list of symptoms with remedies. This text has four major sections, each named by a heading that tells what kind of section it is. The order is not arbitrary, though it is not the only order that could work. Background comes first because every later section depends on the idea that decomposers produce heat and need food, water and oxygen. The procedure comes second because the results cannot be understood unless the reader knows how the pile was built. Results come third because they are a test of the background. Troubleshooting comes last because it applies the background to piles that fail, and a reader who has understood the background can predict the remedies before reading them. A different order is possible: a text could put the results first to catch the reader's interest, but it would then need a preview of the method and cross-references back to the explanation so that the reader could judge the numbers. This author's order is the one that lets each section rely on the one before it without such devices, which is why the later sections can be short.

How each section contributes to the whole and to an understanding of the topic. To analyze contribution, ask two questions of each section: what would the whole text lose without it, and what does the reader understand about the topic after it that they did not understand before? Without the background, the procedure is a recipe with no reasons, and step 3's two-to-one mix looks like superstition. Without the procedure, the results are numbers from a pile of unknown construction, and nobody could repeat them. Without the results, the background is an untested claim; the results supply the one comparison that tests it, a 1-meter pile that heated and a 40-cm pile that barely warmed. Without troubleshooting, a reader whose pile smells cannot connect the smell to the oxygen sentence in the background. The section headings do work of their own: they tell the reader what kind of reading each section needs, so the reader slows down and follows steps in the procedure, reads the results as a sequence in time, and reads the troubleshooting as a lookup table.

Analyzing the author's purpose in each kind of section. Purpose is what the author wants the reader to be able to do after reading. “To inform” is too vague to be an analysis. The purpose of an explanation is understanding: after the background, the reader can say why a pile heats and why size matters. Its signals are present-tense general statements and cause words such as because and so. The purpose of a procedure is performance: after it, the reader can build the pile. Its signals are imperative verbs, numbered steps, quantities and cautions such as “do not use meat.” The purpose of discussing an experiment is judgment: after the results, the reader can say what the readings show, what the class expected, what surprised them, and what they could not tell apart. Its signals are past tense, dated readings, comparisons with a prediction, and limits such as “they could not tell which of the two mattered more.” One text can therefore have three purposes in three sections, and a good analysis names which purpose each section serves and quotes the signal that shows it.

Why the author includes the experiment at all. An author who only wanted readers to build a pile could stop after the procedure. The results section is there because the author wants readers to see the background being tested, to see the surprise on day 7, and to learn that turning restored the heat without proving which cause was responsible. Analyzing purpose means noticing that last sentence: the author discusses the experiment partly to show how a careful class limits its own conclusion. The 40-cm pile is included for the same reason; it is the comparison that makes the size claim more than an assertion.

The misconception. Students often say the purpose of a science text is “to inform” or “to teach about compost” and stop. That names the topic, not the purpose, and it cannot distinguish the sections. A second misconception is that the sections could go in any order because each is complete on its own. They are not complete on their own: the results refer back to the background (“as the background section predicts”) and to the procedure (“following the procedure”), and the troubleshooting is unreadable without the oxygen and food-mix ideas.

A fully worked model. Question: how does the results section contribute to an understanding of the topic, and what is the author's purpose in discussing the experiment? Step 1, name the section's job: it reports dated temperature readings from one pile and one smaller pile. Step 2, find what it adds that no other section gives: the rise to 62 degrees by day 7 and the small pile's failure to pass 24 degrees are the only evidence in the text that the background is right about size; the fall to 55 and the recovery to 60 after turning are the only evidence about oxygen and food. Step 3, name the purpose from the signals: past tense and dates show discussion of an experiment; “they had not expected” shows the author wants the reader to see a prediction meet a surprise; “they could not tell which” shows the author wants the reader to see a conclusion limited to what turning can show. Step 4, state the analysis: the results section turns the background from a claim into a tested explanation and models how to report an experiment honestly, and the author's purpose in discussing it is to let the reader judge the evidence, not merely to prove the procedure works.

Worked contribution analysis: Remove the procedure section and reread. The results now say a class built a pile “following the procedure,” but there is no procedure, so the two-to-one mix, the 1-m height and the turning rule are unknown; the 40-cm comparison loses its meaning because the reader does not know the intended height was 1 m. The troubleshooting still makes sense, because it depends on the background, not on the steps. So the procedure's contribution is specific: it makes the results repeatable and gives the size comparison its reference point.

Worked purpose analysis: Compare two sentences. “In a heap about a cubic meter or larger, the middle is insulated by the outside, heat builds up, and the center can climb well above 50 degrees Celsius.” Present tense, a general claim, a cause chain: this is explanation, and its purpose is understanding of why size matters. “Push a long-stemmed compost thermometer into the center and record the temperature at the same time each day.” Imperative verbs, an instrument, a timing rule: this is procedure, and its purpose is a reader who can measure. Both sentences are about the pile's temperature; their purposes differ, and the grammar shows it.

Worked reordering test: Suppose the troubleshooting came first. A reader would meet “too many greens” before greens are defined in step 2 and “too packed” before the oxygen idea in the background. The remedies would be a list to memorize rather than consequences to predict. Putting troubleshooting last lets the author rely on everything the reader now understands, which is why the section can be short. The author's structure is a decision about what the reader knows at each point.

Structure map: Draw four boxes in the text's order. In each, write the heading, the kind of section (explanation, procedure, experiment discussion, or application), the purpose in one phrase (understand why, be able to do, judge the evidence, fix a problem), and one quoted signal that shows the purpose. Draw arrows for every place a later section relies on an earlier one, and label each arrow with the idea it carries (heat from decomposers, the two-to-one mix, the 1-m height, oxygen).

Independent performance: Write a two-paragraph analysis. Paragraph one: how the four sections are organized and how each contributes to the whole and to understanding why a pile heats; name what would be lost if one section were removed. Paragraph two: the author's purpose in the background, the procedure and the results, each supported by a quoted signal, and an explanation of why the author chose to discuss an experiment rather than stop after the procedure. Success criteria: every section is named with its kind and its purpose; at least three quotations are used as signals of purpose; at least two dependencies between sections are identified with the specific idea that crosses them; the words inform and teach do not appear as your answer to purpose; and every temperature you mention matches the text.