Water for Schools
Menu

Lesson plan Grade 8 Health & Consumer Science

Vandermeer Well Nitrate Test: A Grade 8 Scientific Notation Lesson

A grade 8 health lesson where students read a fictional private-well nitrate test, compare it to a guideline, and express the tiny concentrations in scientific notation.

Objectives

  1. Students will compare a private-well nitrate reading to a stated guideline and find the difference.
  2. Students will express small concentrations in parts per million using scientific notation.
  3. Students will explain why a private-well household must test its own water.

Vocabulary

Nitrate
Nitrate is a form of nitrogen that plants use as food. It gets into water from fertilizer, animal waste, and septic systems, and too much of it is unhealthy for both people and streams.
Parts per million (ppm)
Parts per million tells how many tiny bits of a substance are mixed into a million bits of water. Scientists use it to measure very small amounts of chemicals in water.

Also: scientific notation, guideline

Teacher overview

Homes on city water receive an annual water quality report, but households that draw their water from a private well are responsible for testing it themselves. One thing many well owners watch for is nitrate, which can wash into groundwater from fertilizer or septic systems and which can be a health concern, especially for infants under six months. This lesson uses a fictional well test to give students practice comparing a reading to a guideline and writing very small concentrations in scientific notation. A common misconception is that a concentration in parts per million is a large amount; scientific notation makes clear just how small these numbers are.

Procedure

Hook (5 min): Ask whether anyone knows a home that gets its water from a well rather than from a town system. Explain that no utility mails those homes a water quality report, so the family has to arrange testing. Pose the question: how would you know if your own well water met a safety guideline?

Direct instruction (12 min): Introduce the fictional Vandermeer family well near the town of Cobblehill and model the scientific notation method on a value that differs from the handout. In fresh water such as well water, 1 milligram per liter is about equal to 1 part per million, so a reading of 5 parts per million means 5 out of 1,000,000, which is 0.000005, or 5.0 times ten to the negative sixth power. Write the steps on the board so students can follow the place-value reasoning.

Guided practice (12 min): In pairs, students complete handout items 1 through 4, comparing the well reading to the guideline and writing the first two values in scientific notation. Circulate and check that students count decimal places carefully.

Independent practice (11 min): Students complete handout items 5 through 7 on their own, working with a post-treatment reading and comparing two concentrations using their exponents.

Closure and exit ticket (5 min): Students complete handout item 8, a short written explanation of why a private-well family must test its own water, and hand it in. Read a few responses aloud to close.

Vandermeer Well Nitrate Test: A Grade 8 Scientific Notation Lesson — Grade 8 Health & Consumer Science
Name: ____________________________ Date: ______________

Student Handout

Suppose the Vandermeer family, who live on a private well near the fictional town of Cobblehill, received the lab report below. In this scenario, the county health office suggests keeping nitrate at or below a guideline of 10 mg/L, and in fresh well water like this, 1 mg/L is about equal to 1 part per million.

Test Nitrate reading
First-draw sample 12 mg/L
After treatment unit installed 3 mg/L
  1. The first-draw sample read 12 mg/L. Is that above or below the scenario guideline of 10 mg/L, and by how much?
  2. What percent of the 10 mg/L guideline is the 12 mg/L first-draw reading?
  3. Write the first-draw reading of 12 parts per million as a decimal fraction (12 out of 1,000,000), then in scientific notation.
  4. Write the 10 mg/L guideline (10 parts per million) as a decimal fraction, then in scientific notation.
  5. After the family installed a treatment unit, the nitrate reading dropped to 3 mg/L. What percent of the 10 mg/L guideline is that?
  6. Write the treated reading of 3 parts per million in scientific notation.
  7. Using your scientific-notation answers to items 3 and 6, how many times larger was the first-draw nitrate than the treated reading?
  8. Explain why a family on a private well must arrange their own testing, while a household on city water can read the utility's annual water quality report instead.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 2 mg/L above the guideline.
    12 mg/L minus the 10 mg/L guideline equals 2 mg/L above the scenario guideline.
  2. Answer: 120 percent.
    12 divided by 10, times 100, equals 120 percent of the guideline.
  3. Answer: 0.000012; 1.2 times ten to the negative fifth.
    12 parts per million is 12 out of 1,000,000, which is 0.000012, or 1.2 times ten to the negative fifth power.
  4. Answer: 0.00001; 1.0 times ten to the negative fifth.
    10 parts per million is 10 out of 1,000,000, which is 0.00001, or 1.0 times ten to the negative fifth power.
  5. Answer: 30 percent.
    3 divided by 10, times 100, equals 30 percent of the guideline.
  6. Answer: 3.0 times ten to the negative sixth.
    3 parts per million is 3 out of 1,000,000, which is 0.000003, or 3.0 times ten to the negative sixth power.
  7. Answer: 4 times larger.
    Dividing 1.2 times ten to the negative fifth by 3.0 times ten to the negative sixth gives 0.4 times ten to the first power, which equals 4.
  8. Answer: A private well is not covered by a utility report.
    No utility tests or reports on a private well, so the family must arrange sampling themselves, while a city household can rely on the required annual report for its treated water.

Differentiation

Support

Provide a place-value chart showing where the digit lands for one part per million, one part per hundred thousand, and so on, so students can line up the decimal before converting. Allow a calculator with a scientific-notation display for items 3 through 7.

Extension

Ask students to suppose the guideline were tightened to 8 mg/L and to determine, with reasoning, both readings' new percent-of-guideline values and whether the treated water would still pass. Have them express the new guideline in scientific notation as well.

ELL supports

Pre-teach nitrate, guideline, and reading with a simple labeled picture of a well and a test tube. Provide sentence frames for item 8, such as "A well family must test because ___, but a city family can ___."

Extensions

Students can explain, using only the scenario and their own reasoning, why testing right after a treatment unit is installed and then again several months later would give a family more confidence than a single test. A short written recommendation of a testing schedule turns the math into a practical household plan.