Write informative/explanatory texts, including the narration of historical events, scientific procedures/experiments, or technical processes.
Common Core State Standards, Grades 11-12, Writing: History, Science & Technical Subjects · Read it at the source · Checked October 14, 2026
What WHST.11-12.2 Means in Plain English
Seniors explain a process, like how blood holds its pH, so each idea rests on the one before. They pick the most significant facts, add a figure where it helps, use precise terms and an analogy where the concept gets heavy, and close on why it matters.
Grades 9 to 10 (WHST.9-10.2) connect ideas and choose sufficient facts. Grades 11 to 12 build each element on the last, choose the most significant facts, and use analogy or metaphor to manage complexity. This last band is the college and career readiness goal for explaining.
WHST.11-12.2 I Can Statements
I can order an explanation so each idea builds on the last.
I can choose the most significant facts for my reader.
I can use an analogy to make a complex process clear.
WHST.11-12.2 Worked Example
Both students explained the same chapter to readers with a year of chemistry; only one built the idea a step at a time.
Prompt
In health sciences, explain how the bicarbonate buffer system keeps the pH of blood between 7.35 and 7.45, for readers who have taken one year of chemistry. Include what happens when acid enters the blood, the roles of the lungs and the kidneys, and why such a narrow range matters.
Not YetBlood has a pH of about 7.4, and the body uses buffers to keep it that way. Buffers are important because they balance acids and bases. The lungs and kidneys also help with pH, and if it gets too high or too low a person can get sick.Each sentence names a part, but none builds on the one before it: the reader never learns what a buffer does with an acid, how the lungs connect to it or why the kidneys matter. “Balance acids and bases” is vague where precise terms are needed, and the close states a consequence without the reason the range matters.
Meets the StandardBlood stays between pH 7.35 and 7.45 because it carries its own chemical defense, a buffer pair of carbonic acid and bicarbonate. When acid enters the blood, as when sprinting muscles release hydrogen ions, bicarbonate binds those ions and becomes carbonic acid, which splits into water and carbon dioxide. Bicarbonate works like a sponge: it soaks up extra hydrogen ions before they can drag the pH down. The lungs wring the sponge out, since faster breathing exhales the carbon dioxide and pulls the reaction toward consuming still more acid within minutes. The kidneys work on a slower clock, excreting hydrogen ions and returning fresh bicarbonate to the blood over hours to days. The narrow range matters because enzymes and other proteins hold their working shape only within it, so when the buffer is overwhelmed, as in a diabetic crisis or failing lungs, a chemistry problem becomes a medical emergency.Each element rests on the one before: the buffer pair, then what it does with acid, then the lungs that clear its product, then the slower kidneys. The facts are the significant ones for a reader with a year of chemistry, terms like hydrogen ions are used precisely, and the sponge analogy carries the hardest step without replacing the chemistry. Varied transitions (when, since, so) link the sections, and the close names why the range matters.
Moves to Use
Open with the one idea every later sentence depends on.Add each new element only after the one it rests on.Pick the facts this reader needs and leave the rest for the textbook.Use an analogy for the hardest step, then return to the precise terms.Close on why the topic matters, not on a summary of it.
Common Mistakes with WHST.11-12.2
A list of parts, not an explanation
Buffers, lungs and kidneys each get a sentence that never mentions the others
Try this: Have students write “because” or “which means” between each pair of sentences, then rewrite wherever the link does not hold.
An analogy that replaces the science
“Bicarbonate is like a sponge,” and the chemistry never appears
Try this: Require every analogy to sit next to the precise term it explains, and ask where the comparison stops being true.
Every fact the textbook offers
Three paragraphs on blood plasma before the buffer appears
Try this: Ask students to rank their facts by how much the reader needs each one, then cut the bottom third before drafting.
In the strong response, what does bicarbonate do when acid enters the blood?
It binds the hydrogen ions and becomes carbonic acid, which splits into water and carbon dioxide.
Which step does the sponge analogy carry, and how does the response return to precise terms?
It carries the buffer soaking up hydrogen ions; the next sentences return to the chemistry of the lungs exhaling carbon dioxide and the kidneys returning bicarbonate.
Why does the weak response fall short of WHST.11-12.2a?
It names the buffer, the lungs and the kidneys separately, so no element builds on the one before and the reader never sees how they connect.