Write informative texts that narrate a historical event and report a scientific procedure

Learning goal: Write informative/explanatory texts in history, science and technical subjects, including the narration of a historical event and the report of a scientific procedure or experiment: establish a thesis statement that presents information, introduce the topic and preview what follows, organize ideas into broader categories with headings, graphics and multimedia where useful, develop the topic with relevant facts, definitions, concrete details and quotations, use varied transitions, use precise domain-specific vocabulary, keep a formal style and objective tone, and provide a concluding section that follows from the information.

An informative text's main purpose is to explain, not to argue. Its thesis presents information ("A pendulum's period depends on its length") rather than a position that must be defended against opponents. It may still contain inferences, as a historical narration does when it says why one event led to another, but it marks them as inferences and does not set out to answer an opposing claim. The same subject can be treated either way: the previous lesson argued that length, not mass, controls the period, because there the question was treated as open and a counterclaim had to be answered from measurements; here the relationship is presented as established, for the reader to understand. Genre follows the writer's purpose and the state of the question, not the topic. Two kinds of informative writing come up constantly in history and science classes and are worth learning as forms: the narration of a historical event, which tells what happened in order and explains why the order matters, and the lab report, which narrates a scientific procedure so exactly that another person could repeat it. A technical process (how to calibrate a scale, how a lock on a canal works) is written the same way as a procedure.

Establish a thesis statement to present information. The thesis of an informative text tells the reader what they will understand at the end. For the lab report: "When the length of a pendulum is increased, the time for each swing increases, while changing the mass of the bob has no measurable effect." For the historical narration: "Calder Bend's decline unfolded in three stages: the railroad's decision, the loss of the wagon trade, and the departure of families." Both sentences promise a structure, and the rest of the text delivers it.

Introduce the topic and preview; organize into broader categories with formatting. The introduction names the topic, says why it matters and previews the sections. Then the body groups details into broader categories rather than listing them in the order they were noticed. A lab report uses the categories the discipline expects: Question, Materials, Procedure, Results, Analysis, Conclusion. A historical narration groups events into stages or causes. Headings make those categories visible, a table or graph shows the data more clearly than a paragraph can, and, when the text is published on a screen, a photograph of the apparatus or a short video of the procedure can be included as multimedia. Every graphic is referred to in the prose; a graphic of measured quantities is labeled with its units, and a photograph or a process diagram carries labels and a caption instead. A well-made visual can develop the topic on its own, but a sentence that tells the reader what to notice in it makes sure that it does.

Develop the topic with relevant, well-chosen facts, definitions, details and quotations. "Well-chosen" means selected for what they contribute. In the lab report, the definition of period is essential, the color of the string is not. In the narration, the storekeeper's exact words about the wagons are a concrete detail worth quoting because they show the mechanism; the weather that year would be relevant only if a source connected it to the decline. Quotations are marked as quotations and attributed to their source; numbers carry their units.

Use appropriate and varied transitions. Narration uses time transitions: in 1861, the following spring, by 1870, meanwhile. Procedures use sequence transitions: first, next, after the tenth swing, finally. Explanations of results use logical transitions: as a result, in contrast, this pattern suggests. Vary them, but choose each for the relationship it signals. Then is right for a procedure step; it is wrong for two events whose order the sources do not establish.

Use precise language and domain-specific vocabulary. Precision means the word that fits exactly: period rather than "the time it takes", bob rather than "the thing on the end", canal landing rather than "the place by the water", enlisted rather than "joined up". Define a domain word the first time it appears if the audience may not know it. Precise language also means honest numbers: "about 14 seconds" when the stopwatch read 14.2 s is acceptable rounding; "exactly 14 seconds" is not.

Maintain a formal style and objective tone. Objective tone reports what was observed and what the sources say, and keeps the writer's feelings out: not "our results were awesome" but "the results matched the prediction within 0.2 s". In historical narration, objectivity means distinguishing what a source states from what the writer infers: "the letter reports that six shops closed" (stated) versus "these closures probably drove families to leave" (inferred, and marked as such).

Provide a concluding statement that follows from the information. The conclusion of a lab report answers the question that opened it, states the pattern in the data, and notes limits. The conclusion of a narration says what the sequence of events amounted to. Neither adds new information.

Original model lab report — Does Length or Mass Control a Pendulum's Period? This is a model with class-trial numbers; your own measurements will differ slightly.

Question. Which variable, string length or bob mass, changes the period of a pendulum? The period is the time for one complete swing, out and back.

Materials. String, a ring stand with a clamp, two metal washers of different mass (one about twice the other), a meter stick, a stopwatch.

Procedure. First, tie one washer to the string and clamp the string so that the distance from the clamp to the center of the washer is 25 cm. Next, pull the washer aside by no more than about 10 degrees and release it without pushing. Start the stopwatch on release and stop it after ten complete swings; dividing by ten gives one period and reduces timing error. Repeat the timing three times and record the average. Then lengthen the string to 50 cm and to 100 cm and repeat. Finally, at 50 cm, replace the washer with the heavier one and time ten swings again.

Results. Ten swings took 10.0 s at 25 cm, 14.2 s at 50 cm and 20.1 s at 100 cm (see the bar chart). With the heavier washer at 50 cm, ten swings took 14.3 s. The three repeated timings at any one length differed from one another by up to 0.2 s.

Analysis. The time increased every time the length increased. Doubling the length from 25 cm to 50 cm multiplied the time by about 1.4, and doubling it again to 100 cm multiplied it by about 1.4 again, so quadrupling the length roughly doubled the period, from 1.00 s to 2.01 s. In contrast, doubling the mass changed the time by 0.1 s, which is smaller than the difference between repeated trials at the same length.

Conclusion. For small swings, the period of this pendulum depended on its length and not on the mass of its bob. The report cannot say what happens at large angles, because no trial exceeded about 10 degrees.

Original model historical narration — The Track Goes North (fictional town, fictional sources). Calder Bend, a canal landing in the model county, declined in three stages between 1861 and 1870, each recorded in a different kind of source.

The decision, 1861. In 1861 the county newspaper announced that the railroad company had surveyed its line through Reedsville, "where the ground is level," and would not bring the track to Calder Bend "on account of the river bluffs." At the time, the town's population, 1,190 by the previous year's count, had barely changed in a decade.

The trade, by 1868. Once the track opened, farmers could load grain onto rail cars at Reedsville instead of waiting for a canal boat at the landing. A storekeeper wrote to his brother in 1868 that "the grain wagons go north instead of down to our landing." Six shops on Water Street, he reported, had closed. The letter is one man's view, but it describes the mechanism that the population figures only imply.

The people, by 1870. The county table for 1870 recorded 860 residents, 330 fewer than in 1860. Meanwhile Reedsville had grown to 1,480. The 1880 county history adds that some young men had enlisted during the war and others "found work in the cities after the war," so the decline had more than one source.

In sum, the sources record three stages: a railroad decision in 1861, six shops closed by 1868 and 330 fewer residents in 1870 than in 1860. That the decision cost the town its trade, that the lost trade closed the shops, and that the closures sent families elsewhere is this narration's inference from the order of the sources and from the storekeeper's account; the sources record each stage but do not say where most of those families went.

Worked category repair: A student's lab report lists observations in the order they happened: "We tied the string. It was 25 cm. The washer swung. It took 10.0 seconds for ten swings. Then we made it 50 cm..." Everything is there, but the reader cannot find the results without reading the whole story. Reorganized into broader categories, the same information becomes a Procedure paragraph (what was done, in sequence) and a Results paragraph or table (what was measured, by length). The headings let a reader who wants only the data go straight to it.

Worked precision and objectivity edit: Draft sentence: "The long one was way slower, which was really cool and proved our idea." Revised: "At 100 cm the period was 2.01 s, about twice the 1.00 s period at 25 cm, which matched the prediction that period increases with length." The revision replaces "the long one" with the measured length, "way slower" with the numbers, "really cool" with nothing, and "proved" with "matched the prediction", because one trial set supports a pattern rather than proving a law.

Worked transition choice in narration: Draft: "The railroad chose Reedsville. Then six shops closed. Then the population fell." The word then claims a sequence, and the sources support only part of it. The notice is dated 1861, so the decision came first. The letter, written in 1868, reports closures that had happened by then, and the 1870 table reports a population that had fallen by then; a document's date bounds an event without dating it, so the sources do not show whether the shops closed before the families left or as they left. The draft hides both what the dates establish and what they do not. Revised: "In 1861 the railroad chose Reedsville. By 1868, according to the storekeeper's letter, six shops had closed. By 1870 the county table shows 330 fewer residents than a decade earlier." Dated transitions let the reader check the order against the sources.

Worked multimedia decision: The class will publish the lab report on its website, where multimedia is possible. Three candidates: a photograph of the apparatus, a 20-second video of ten swings being timed, and a video of the whole class session. The photograph earns its place: a reader who has never seen a washer on a clamped string can check the setup at a glance, and labels can name the clamp, the string and the washer. The 20-second clip earns its place beside the Procedure, because it shows what "release it without pushing" and "one complete swing, out and back" look like, which words convey slowly; its caption says what to watch for. The session video fails the test: nothing in it helps a reader understand what the text and the chart do not give faster, so it is left out. The standard's condition is "when useful to aiding comprehension", so each item is judged by what it helps this reader understand, and each one that stays is referred to in the prose like any graphic. On paper, the clip becomes a still image or a sentence.

Worked graphic reference: "See the chart" tells the reader nothing. Revised: "The bar chart shows the time for ten swings rising from 10.0 s at 25 cm to 20.1 s at 100 cm; the bars grow more slowly than the lengths do, which is why quadrupling the length only doubles the time." The sentence directs the reader to the pattern the graphic is there to show.

Structure task: Take a procedure you have actually carried out in science or a technical class this year (or the pendulum model). Write the six lab-report headings and, under each, one or two sentences of the content that belongs there. Then write the same information as a paragraph without headings. Compare the two with a partner: which one lets a reader find the results in under ten seconds? Separately, take three dated events from your current history unit and write one paragraph of narration using dated transitions, marking each sentence S (stated by a source) or I (inferred by you).

Independent performance: Write either a complete lab report (400–500 words plus one table or graph) on a procedure you performed, or a 400- to 500-word narration of a historical event from your current unit using at least two sources. Success criteria: (1) a thesis statement that presents the information to come; (2) an introduction that previews the sections, with headings that group details into broader categories; (3) at least one graphic or table that the prose refers to, with a caption and with units on any measured quantity, and, if the text is published on a screen, a one-sentence reason for including or leaving out a photograph or short video; (4) relevant facts, definitions of domain words at first use, concrete details and at least one attributed quotation; (5) varied transitions that correctly signal time, sequence or logic; (6) formal style and objective tone, with stated facts distinguished from inferences; (7) a concluding section that answers the opening question or sums up the sequence and names one limit of the information. A partner should be able to repeat your procedure, or retell your event in order, from your text alone.