Water Quality Lessons



Class Periods




Subject Areas



Students will take data using a series of different measurements. They will compare their results and determine if any of the data is meaningful, precise, reliable, or accurate.


  • Which data is meaningful?

  • How do we decide that data is meaningful?

  • What do we look for when we analyze data?

  • What does a precise result tell us about an experiment?

  • What does an accurate result tell us about an experiment?

Materials and Resources


  • 3 buckets of water with different pH (add baking soda to one bucket or vinegar to another).
  • Beakers so each student group can a sample from each bucket.
  • pH probe pH paper

Before you get started

Tips for Teachers

For the purpose of this lesson, we will use the words in the following ways: Precise refers to specificity. Reliable refers to consistency, Accurate is for close to the true value. Meaningful means that you can learn something new or draw a conclusion from the data. Doing this lesson with water of different pH’s is a level 1 activity. For a slightly more advanced class, you could use water from different parts of the river. However, the difference in pH will be much more subtle, so subtle that your instruments might not capture it!


When students are presented with data, they often draw immediate conclusions from that data. This is especially tempting with the water quality data (eg: My oysters died because the DO level was low, etc.) This lesson affords your students the opportunity to analyze when data is important and what makes it meaningful. They will then examine the difference between precise and accurate measurements and discuss what each one reveals about the experiment.

Instruction Plan


Have students taste three cups of water, one with lemon juice, one with baking soda, and one with nothing added. Ask them to describe the difference.  Ask students what is the difference between the water quality? How would they describe the difference between the three kinds of water? What words would they use. Introduce the words acid, base, and pH. Have students consider what makes something take acidic or basic.

Now, introduce the word “accurate.” Have students discuss whether or not they think their earlier descriptions are accurate. Why or why not?

Is “more” or “less” an accurate measurement? What about “the same?” Is that an accurate measurement? Is it a precise measurement? Why or why not?

Now, ask students for an accurate but imprecise description and/or a precise but inaccurate description.


Now, explain to students that they are going to investigate precision and accuracy with pH.  Put the mystery solution at the front of the room. Have students test 3 “mystery solutions” with 2 different tests. Have them fill out the table below.



tool or test name

Solution A

Solution B

Solution C


pH Paper




pH Paper




pH Paper




pH Paper




  1. On the board, put up all data that students have gotten from all methods and samples in a larger format table like the one above.
  2. Now, have a discussion with students about the precision, accuracy,  and reliability of the different measurements and what it means. Is there any meaningful data? Why or why not?
  3. Some sample discussion questions include:
    • If all the results are very close except for one, what does that mean about the result? What does that mean about the measurement?
    • If the results are precise but not accurate, what do you think the problem is?
    • If one result is accurate but the rest are not, what do you think that says about the measurement?
    • Which method gave you more precise results? Explain why
    • Which method gave you more accurate results? Explain why
    • If the probe gave you precise results but you know they are not accurate, what might you do?
    • What is the most accurate that the pH paper can be? Explain why.


Ask students what they might change about the experiment to

  1. Make their results more precise

  2. Make their results more accurate.

  3. Make their results more reliable.

  4. Make their results more meaningful?


CCLS - ELA Science & Technical Subjects

    • Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.
    • Integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, or table).

CCLS - Mathematics

    • Describing the nature of the attribute under investigation, including how it was measured and its units of measurement.

NGSS - Cross-Cutting Concepts

  • Patterns

    • Patterns can be used to identify cause and effect relationships.
  • Scientific Knowledge Assumes an Order and Consistency in Natural Systems

    • Science assumes that objects and events in natural systems occur in consistent patterns that are understandable through measurement and observation.

NGSS - Science and Engineering Practices

  • Analyzing and Interpreting Data

    • Analyze and interpret data to determine similarities and differences in findings.
  • Constructing Explanations and Designing Solutions

    • Apply scientific ideas to construct an explanation for real-world phenomena, examples, or events.

NYC Science Scope & Sequence - Units

  • Grade 7, Unit 2

    • Energy and Matter

NYS Science Standards - Key Ideas

  • PS Key Idea 3

    • Matter is made up of particles whose properties determine the observable characteristics of matter and its reactivity

NYS Science Standards - Major Understandings

    • Substances have characteristic properties. Some of these properties include color, odor, phase at room temperature, density, solubility, heat and electrical conductivity, hardness, and boiling and freezing points.
    • Substances are often placed in categories if they react in similar ways. Examples include metals, nonmetals, and noble gases.

NYS Science Standards - MST

    • Students will apply the knowledge and thinking skills of mathematics, science, and technology to address real-life problems and make informed decisions.