Writing prompt Grade 7 English Language Arts
Why the Soap Will Not Lather in Fairholm: An Explanatory Prompt
A grade 7 explanatory writing prompt on hard water, with a background brief, a planning organizer, a full exemplar essay, and a four-level rubric.
Objectives
- Students will define a technical term in their own words for a general audience.
- Students will explain a cause-and-effect chain from rock to faucet in order.
- Students will distinguish what a condition affects from what it does not affect.
Vocabulary
Key words: hardness, dissolve, scale, mineral, softener
Teacher overview
Families in the fictional town of Fairholm complain about spotted glasses, thin lather, and a white crust on the kettle, and many of them assume the water is dirty. Hardness is a genuine nuisance with real costs, yet it is not a health contaminant, which makes it a good subject for explanatory writing rather than argument. Students write for a school newsletter audience that wants to know what hardness is, where it comes from, and what it does and does not affect.
Prompt
Background brief: water in the town of Fairholm.
Fairholm gets its water from wells drilled into limestone. Limestone is a rock made mostly of calcium carbonate, a mineral that contains calcium. Rain soaks into the ground and moves slowly through cracks in that rock. Along the way, small amounts of calcium and magnesium dissolve into the water. Water that carries a lot of these two minerals is called hard water.
The Fairholm Water Company measures hardness in milligrams per liter. Fairholm's wells test at about 240 mg/L, which laboratories describe as very hard. A neighboring town that draws from a sandy aquifer tests near 60 mg/L, which is considered soft.
Hardness changes how water behaves. Soap reacts with calcium and magnesium instead of making suds, so it takes more soap to wash anything, and a dull film is left on skin, dishes, and dark clothes. When hard water is heated, some of the minerals come out of the water and stick to metal. That crust is called scale. Scale coats the inside of water heaters, kettles, and pipes, and a heater with a thick layer of scale uses more energy and fails sooner.
Hardness is not a health problem. Calcium and magnesium are minerals people eat in food every day. The federal government sets health limits for contaminants such as arsenic and nitrate, and hardness is not one of them. It is treated as a nuisance, not a danger.
Families can buy a home softener, which trades the calcium and magnesium for sodium and needs a bag of salt every few weeks. A softener also sends salty rinse water down the drain, which the wastewater plant cannot remove. The water company could soften all of the town's water at the plant instead, which would cost every customer more each month whether or not that household minded the spots.
Your task. Write an explanatory essay for the Fairholm Middle School newsletter. Your readers are families in town. Explain what hard water is, why Fairholm's water is hard, and what hardness does and does not affect. Use details from the background brief. Do not argue for or against softening. Your job is to explain the situation clearly enough that readers could decide for themselves.
Planning Organizer
Fill in every row before you draft. Each row connects to a criterion on the rubric.
| Category | Your notes |
|---|---|
| Definition: what hard water is, in your own words | |
| Cause: why Fairholm's water carries these minerals | |
| Evidence: two details or figures from the brief | |
| Effect 1: what hardness does to soap | |
| Effect 2: what hardness does to heated water and pipes | |
| What hardness does not do | |
| Precise words you will define for your reader | |
| Conclusion: one sentence that closes without repeating your opening |
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Exemplar & Rubric
Exemplar response
If the soap in your shower will not lather and the kettle has a white crust inside it, the cause is not dirt in the water but hardness. Hard water is water that carries a large amount of two dissolved minerals, calcium and magnesium. Most of the complaints families have about our water come back to those two minerals.
The reason lies in the rock under the town. Fairholm's wells reach into limestone, a rock made mostly of calcium carbonate, a mineral that contains calcium. Rain soaks into the ground and travels slowly through cracks in that rock, and a little of the rock dissolves into the water as it passes. By the time the water reaches a well, it carries the minerals with it. The water company measures hardness in milligrams per liter, and Fairholm's wells test at about 240 mg/L, which laboratories call very hard. A nearby town that pumps from sand instead of limestone tests near 60 mg/L, which is soft. The difference is the rock, not the care taken by either town.
Hardness shows up in two everyday ways. First, soap reacts with the calcium and magnesium instead of making suds, so washing takes more soap and leaves a dull film on skin, dishes, and dark shirts. Second, heating hard water makes some of the minerals come out and stick to metal as a crust called scale. Scale builds up inside water heaters, kettles, and pipes. A heater lined with scale has to work harder to warm the water, so it uses more energy and wears out sooner.
It is worth being clear about what hardness does not do. Calcium and magnesium are minerals people eat in food every day, and hardness is not one of the contaminants the federal government sets health limits for. Spotted glasses are annoying, and a shortened water heater life costs money, but neither one means the water is unsafe to drink.
Families who want softer water can install a home softener, which trades the calcium and magnesium for sodium and needs a bag of salt every few weeks. That salty rinse water goes down the drain, and the wastewater plant cannot take the salt back out. The water company could also soften the whole town's supply at the plant, which would raise every customer's monthly bill. Knowing what hardness is, where it comes from, and what it does makes those choices easier to weigh.
Rubric
| Criterion | Emerging | Developing | Proficient | Advanced |
|---|---|---|---|---|
| Definition and focus | No definition of hard water is given | A definition is attempted but leaves out the minerals | Defines hard water as water carrying dissolved calcium and magnesium | Defines the term and orients the reader with a specific opening detail from town life |
| Cause explained | The cause is missing or wrong | Names limestone without connecting it to the well water | Traces rain through limestone to the well in order | Traces the chain and explains why a nearby town's water differs |
| Evidence from the brief | No details from the brief appear | One detail is copied without explanation | Uses at least two details or figures and explains what each shows | Selects details for the reader's purpose and interprets the comparison between towns |
| Effects and non-effects | Effects and health risk are confused | Names one effect; the health point is unclear or wrong | Names the soap effect and the scale effect, and states that hardness is not a health problem | Explains the mechanism behind both effects and separates cost from safety without dismissing either |
| Organization and conventions | Ideas are unordered; errors block meaning | Some grouping; transitions are thin | Clear paragraphs with transitions and a closing sentence | Purposeful order, precise vocabulary defined in context, nearly error free |
Differentiation
Support
Provide the organizer with the definition and cause rows already filled in, so students begin at the evidence row. Give a paragraph-by-paragraph outline card naming what each paragraph must contain, and allow the essay to run three paragraphs instead of five.
Extension
Ask students to add a paragraph explaining why the softener choice is harder for the wastewater plant than for the household, then revise the essay so a reader could not tell which option the writer prefers. Staying neutral in explanatory writing about a contested question is demanding, and it is worth naming that difficulty for students before they revise.
ELL supports
Demonstrate hardness with two jars, one of tap water and one of distilled water, shaking a drop of pure liquid castile soap in each so students see the difference in suds before they read. If local tap water is soft, stir a pinch of Epsom salt into the tap-water jar first. Pre-teach "dissolve," "scale," and "mineral" with the jars in view. Provide sentence frames for the definition and the cause rows, and allow the organizer to be completed in phrases.
Extensions
Students interview an adult at home about spotted dishes, kettle crust, or a softener, then add one quotation to the essay and a sentence explaining how the quotation supports the paragraph it sits in.