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ACTIVITY in Physical Properties, Concentration, Chemical Properties, pH. Last updated January 29, 2024.

Summary

In this activity, students are provided with data regarding the water quality at multiple locations throughout a city. Students will determine which location should be prioritized for cleaning of contaminates. Students will utilize Claim Evidence and Reasoning (CER) to develop a claim that is supported by the data provided.

Grade Level

Middle School

NGSS Alignment

This activity will help prepare your students to meet the performance expectations in the following standards:

  • MS-PS1-3: Gather and make sense of information to describe that synthetic materials come from natural resources and impact society.
  • MS-ETS1-3: Analyze data from tests to determine similarities and difference among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.
  • Scientific and Engineering Practices:
    • Analyzing and Interpreting Data
    • Engaging in Argument from Evidence

Objectives

By the end of this activity, students should be able to

  • Cite strong evidence to support their claim and create a reasoning statement supported by evidence.
  • Analyze and interpret data provided.
  • Engage in argument using evidence.
  • Understand the meaning of water quality, and the general impact of contaminants.

Chemistry Topics

This activity supports students’ understanding of

  • Solutions
  • Concentration
  • pH Scale
  • Physical Properties
  • Chemical Properties

Time

Teacher Preparation: 10 minutes

Lesson: 1 hour

Materials

Safety

  • No specific safety precautions need to be observed for this activity.

Teacher Notes

  • Students should already have an understanding of what a Claim-Evidence-Reasoning statement (CER) is and how to create a CER.
  • A CER graphic organizer may be helpful to give to students. These are readily available on the web for teacher access/use.
  • Depending on student prior knowledge, the teacher could use background information about water quality, such as written materials, and videos.The teacher should choose any or all that you feel to be necessary based on the prior knowledge of your students. For example:

For the Student

Lesson

Background

Water quality is determined by the presence and quantity of contaminants, by physical and/or chemical factors such as pH, sulfates, zinc and turbidity. Humans largely influence all these factors, as they discharge their waste in water and add all kinds of substances and contaminants to water that are not naturally present.

To determine water quality, certified agencies collect samples; small amounts of water, which can be tested in a laboratory. Laboratories test these samples at various locations, and see if they meet water quality standards. In order to assess the need for treatment and the right treatment technology, specific contaminants in water must be identified and measured. Each contaminate has a Maximum Contamination Level (MCL) that determines whether the substance present in the water is considered safe to drink. There are also substances that can be identified through physical properties such as visible characteristics of water; including turbidity and clarity, taste, color and odor of the water.

There are other substances that can be identified by chemical properties such as pH. The pH is the value that determines if a substance is acid, neutral or basic, calculated from the number of hydrogen ions present. It is measured on a scale from 0 to 14, on which 7 means the substance is neutral. pH values below 7 indicate that a substance is acidic and pH values above 7 indicate that it is basic. When a substance is neutral the number of hydrogen atoms and hydroxyl atoms are equal.

Image credit: Wikimedia.org/Heinrich-Boll-Stiftung

Background Questions

Use the information given in the table to determine whether the water sample should be considered safe or unsafe to drink.


Location 		Arsenic
(MCL 0.010) 		Coliform (Bacteria)
(MCL 0)
Park 0.009 3
Church 0.2 0
Mall 0.002 7
School 0.0083 0
Police Dept. 2.1 1
City Hall 0.15 2
Senior Apartments 0.001 0.1
  1. What does “MCL” mean?
  2. If a water sample has a value for a contaminant that is higher than the given MCL, what does that mean?
  3. Is the water sample at the Church considered safe to drink based on the level of arsenic present (MCL = 0.010)?
  4. Is the water sample at the Park considered safe to drink based on the level of coliform present (MCL = 0)?

Instructions

  • Read the background information and use the data table below to determine which location should have top priority to be cleaned up.
  • Be sure to compare each value in the table to the MCL provided to determine if that level of contaminate is considered safe to drink or not safe to drink.
  • You will need to rank each location based on the level of contamination.

Location 		Turbidity
(clarity)

MCL 0 		Sulfates

MCL 250 		pH

MCL6.5-8.5 su

Mercury

MCL 0.002 mg/L

Zinc

MCL 5

Park

3

323

8.7

0.0002

4.5

Church

3

125

5.6

0.08

0.75

Mall

6

249

7.1

0.00006

7

School

0

378

7.6

0.007

5

Police Dept.

0

255

3.3

0.05

2

City Hall

5

350

1.0

0.093

6.75

Senior Apartments

2

197

13.2

0.0008

5.25

Analysis

  1. Explain which type of contaminate had the highest MCL.
  2. Explain which type of contaminate had the lowest MCL.
  3. What factors were used in prioritizing each location’s need for clean up?

Conclusion

Make a recommendation to the mayor of the city using a claim-evidence-reasoning statement. Determine which location should be prioritized by the city and needs to be decontaminated first. Complete the CER organizer (optional) provided.

  • State a claim
  • Cite strong evidence to support your claim (analyze and interpret the data)
  • Create a reasoning statement supported by evidence