Worksheet Grade 8 Health & Consumer Science
Reading Ashwood's Water Quality Report: A Consumer Skills Worksheet
A grade 8 worksheet where students interpret a water utility's annual quality report, comparing measured levels to legal limits using scientific notation.
Objectives
- Students will interpret a water quality report table by comparing measured levels to legal limits.
- Students will express parts-per-trillion and parts-per-million concentrations in scientific notation.
- Students will explain why reading a water quality report is a practical consumer skill.
Teacher overview
Every public water utility in the United States must publish an annual water quality report, sometimes called a Consumer Confidence Report, listing what was measured in the water and comparing it to the legal limit for each substance. Reading that report is a practical consumer skill, similar to reading a nutrition label, but it requires comparing numbers written in very different units, since some substances are measured in parts per million while others, present in much smaller amounts, are measured in parts per billion or parts per trillion. This worksheet has students read a water quality report table for a fictional utility and use scientific notation to make sense of just how small some of these legal limits really are.
Student Worksheet
Ashwood is a fictional water utility used for this worksheet. It published the following results in its 2026 annual water quality report.
| Substance | Ashwood's measured level | Legal limit or action level |
|---|---|---|
| PFOA | 1.2 ppt | 4.0 ppt (systems must comply by 2029) |
| Lead | 3 ppb | 15 ppb action level (dropping to 10 ppb in 2027) |
| Chlorine residual | 1.1 mg/L | 4.0 mg/L (maximum) |
| Turbidity | 0.12 NTU | 0.3 NTU |
What is Ashwood's measured level of PFOA, and is it above or below the legal limit?
What is today's lead action level, and what will it become in 2027?
Based on the table, does Ashwood's water stay under all four limits and levels listed? Explain how you know, using at least two rows of the table.
The PFOA legal limit is 4.0 parts per trillion. Write that limit as a decimal fraction, which means dividing 4.0 by one trillion. Then write your decimal in scientific notation.
The chlorine residual limit is 4.0 mg/L, which is the same as 4.0 parts per million. Write 4.0 parts per million as a decimal fraction. Then write that decimal in scientific notation.
Using your answers to items 4 and 5, compare the two limits as decimal fractions. How many times larger is the chlorine residual limit than the PFOA limit? (Hint: compare the exponents in your two answers.)
Parts per trillion and parts per million both measure concentration. Why do water utilities report PFAS in parts per trillion instead of parts per million?
Explain in your own words what turbidity measures. Then explain why a lower NTU reading is better.
Ashwood's utility manager will present this report at a town meeting. Most residents there have no science background. Use the table to write two sentences in everyday words. Your sentences should tell residents what the PFOA row says about their tap water.
Suppose a utility states that its water met every legal limit. Why might a family still want to read that utility's annual water quality report?
The table notes that the lead action level will drop from 15 ppb to 10 ppb in 2027. Suppose a utility measures a lead level between 10 and 15 ppb today. That utility is under today's action level. Explain why it might still need to take action before 2027.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
Answer: 1.2 ppt, below the limit.
Ashwood's measured PFOA level of 1.2 ppt is lower than the 4.0 ppt legal limit shown in the table.Answer: 15 ppb today, dropping to 10 ppb in 2027.
The table states both figures directly; the 2027 change comes from the Lead and Copper Rule Improvements. The action level tells a utility when it must act; it is not a safe level, because EPA's health goal for lead is zero.Answer: Yes, it stays under all four.
Every measured value in the table (1.2 ppt, 3 ppb, 1.1 mg/L, and 0.12 NTU) is lower than its corresponding limit or level (4.0 ppt, 15 ppb, 4.0 mg/L, and 0.3 NTU).Answer: 0.000000000004; 4.0 x 10^-12.
4.0 parts per trillion means 4.0 out of 1,000,000,000,000, which as a decimal is 0.000000000004, or 4.0 times 10 to the negative 12th power.Answer: 0.000004; 4.0 x 10^-6.
4.0 parts per million means 4.0 out of 1,000,000, which as a decimal is 0.000004, or 4.0 times 10 to the negative 6th power.Answer: 1,000,000. Comparing the exponents, 10^-6 is larger than 10^-12 by a factor of 10^(−6−(−12)) = 10^6, which equals 1,000,000 times larger.
Answer: Because PFAS is considered harmful even in extremely tiny amounts, reporting it in parts per trillion lets regulators set and enforce a limit far smaller than parts per million could meaningfully describe.
Answer: Turbidity measures how cloudy water is, caused by tiny suspended particles; a lower NTU reading means clearer water, which generally indicates more effective filtration and treatment.
Answer: Answers will vary. Example: "Our tap water's PFOA level is 1.2 parts per trillion, well under the federal limit of 4.0 parts per trillion. Water systems must meet that limit by 2029, and ours already does."
Answer: Answers will vary; accept reasoning such as wanting to see results directly rather than rely on a summary, wanting to track trends across several years' reports, or wanting to check factors like taste or hardness that legal limits do not fully cover.
Answer: A utility measuring between 10 and 15 ppb is under today's action level but would exceed the lower 2027 action level, which would require the utility to act, so it may need to add corrosion control treatment or begin replacing lead service lines now rather than waiting until 2027. Ashwood's own reading of 3 ppb is well under both thresholds, so this question asks students to reason about a utility closer to the line than Ashwood is.
Differentiation
Support (below grade level)
Provide the scientific notation steps for item 4 fully worked as a model before students attempt item 5 on their own, and allow a calculator with a scientific notation function for items 4 through 6.
Extension (above grade level)
Ask students to reason, using the table and their answer to item 8, why turbidity is measured differently from PFAS, lead, and chlorine, and to explain why some water quality measurements use a physical scale like NTU instead of a concentration unit like ppt or mg/L.
ELL supports
Pre-teach turbidity, residual, and action level with simple visual comparisons (a jar of clear water next to a jar of cloudy water for turbidity). Allow items 1, 2, and 3 to be answered by circling or underlining the relevant numbers directly in the table rather than writing full sentences.