Students build a saltwater circuit, which is an electrical circuit that uses saltwater as part of the circuit. Students investigate the conductivity of saltwater, and develop an understanding of how the amount of salt in a solution impacts how much electrical current flows through the circuit. They learn about one real-world application of a saltwater circuit — as a desalination plant tool to test for the removal of salt from ocean water.
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standard Network (ASN), a project of JES & Co. (www.jesandco.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.
Click on the standard groupings to explore this hierarchy as it applies to this document.
- Colorado: Math
- 1. read and construct displays of data using appropriate techniques (for example, line graphs, circle graphs, scatter plots, box plots, stem-and-leaf plots) and appropriate technology; (Grades 5 - 8)  ...show
- 4. formulate hypotheses, draw conclusions, and make convincing arguments based on data analysis; (Grades 5 - 8)  ...show
- 2. estimate, make, and use direct and indirect measurements to describe and make comparisons; (Grades 5 - 8)  ...show
- 3. read and interpret various scales including those based on number lines, graphs, and maps; (Grades 5 - 8)  ...show
- Colorado: Science
- 3. interpret and evaluate data in order to formulate logical conclusions (Grades 6 - 8)  ...show
- 4. demonstrate that scientific ideas are used to explain previous observations and to predict future events (for example: plate tectonics and future earthquake activity) (Grades 6 - 8)  ...show
- 2. mixtures of substances can be separated based on their properties (for example: solubilities, boiling points, magnetic properties, densities and specific heat) (Grades 6 - 8)  ...show
- 3. mass is conserved in a chemical or physical change (Grades 6 - 8)  ...show
- 9. electric circuits provide a means of transferring electrical energy when heat, light, sound, magnetic effects and chemical changes are produced (Grades 6 - 8)  ...show
- 1. a controlled experiment must have comparable results when repeated (Grades 6 - 8)  ...show
- Common Core State Standards for Mathematics: Math
- 1. Construct and interpret scatter plots for bivariate measurement data to investigate patterns of association between two quantities. Describe patterns such as clustering, outliers, positive or negative association, linear association, and nonlinear association. (Grade 8)  ...show
- International Technology and Engineering Educators Association: Technology
- F. Knowledge gained from other fields of study has a direct effect on the development of technological products and systems. (Grades 6 - 8)  ...show
- Run an experiment.
- Collect and analyze data.
- Work as part of a team.
- 2 large, wooden Popsicle sticks (available at craft stores)
- 4 pieces insulated copper wire, each 4-6 inches (10-15 cm) long
- 3 plastic cups, 16 ounce (473 ml) size
- 2 plastic spoons
- 9-volt battery
- battery cap, usually with red and black wire leads (available at Radio Shack or hardware stores)
- 3.7 volt light bulb (available at hardware stores)
- 1 miniature light bulb socket (available at hardware stores; use with the 3.7 volt light bulb)
- eye protection (goggles or safety glasses)
- (optional) multimeter and multimeter leads with alligator clips (available at RadioShack)
- Reflection Worksheet, one per person
- Saltwater Density Cards, one card per group
- Saltwater Circuit Worksheet (without Multimeter) or Saltwater Circuit Worksheet (with Multimeter), one per group
- electrical tape
- salt, one 26 oz (737 g) container is enough for all groups, plus some extra
- screwdrivers, to tighten wires in light bulb sockets
- roll of aluminum foil
- triple beam or digital scale, to measure grams of salt
- measuring cups or graduated cylinders, to measure ml of water
- projector, to show the attached Saltwater Circuit Presentation PowerPoint
|closed circuit:||An electrical circuit that is conducting electricity.|
|density:||Mass per unit volume.|
|electrical circuit:||A chain of connected circuit elements.|
|electric current:||The rate of flow of electric charge, measured in amperes (A).|
|input:||The object going into a system.|
|ion:||An atom that has an electrical charge because it has either gained or lost an electron.|
|multimeter:||An electronic measuring device that combines several measurement functions into one unit.|
|open circuit:||An electrical circuit that is not conducting electricity.|
|output:||The object coming out of a system.|
|short circuit:||When electrical current is diverted from all circuit elements to few or no circuit elements other then the battery.|
|system:||An object that receives inputs and transforms them into output.|
|voltage:||Electrical potential difference, measured in volts (V).|
Before the Activity
- Gather materials.
- Cut enough 4-6 inch pieces of insulated copper so each group has four pieces.
- Print out and cut apart the attached Saltwater Density Cards, enough so you have one card per group (the two-page attachment contains 20 different cards, each providing the salt and water measurements to make three different saltwater concentration solutions).
- Make copies of the Saltwater Circuit Worksheet (without Multimeter) or Saltwater Circuit Worksheet (with Multimeter), one per group, depending on whether or not multimeters are available to use.
- Divide the class into groups of two or three students each.
With the Students — Building the Saltwater Circuit
With the Students — Solutions, Data Collection and Analysis
- Saltwater Circuit Presentation (ppt)
- Saltwater Circuit Presentation (pdf)
- Reflection Worksheet (doc)
- Reflection Worksheet (pdf)
- Saltwater Density Cards (doc)
- Saltwater Density Cards (pdf)
- Saltwater Circuit Worksheet without Multimeter (doc)
- Saltwater Circuit Worksheet without Multimeter (pdf)
- Saltwater Circuit Worksheet with Multimeter (doc)
- Saltwater Circuit Worksheet with Multimeter (pdf)
- Have students use goggles or safety glasses for eye protection.
- If not using a battery cap, it is easy to short circuit the battery if the wire ends that are connected to the positive and negative terminals of the battery touch. If they touch, the battery overheats and can cause severe burns.
Activity Embedded Assessment
- For lower grades, only use visual observations (eliminate the multimeter).
- For upper grades, allow students to select several salt-to-water ratios to test electrical conductivity.
PBS Kids Go. Zoom-Saltwater Rocks. WGBH Educational Foundation. Accessed May 1, 2010. http://pbskids.org/zoom/activities/sci/saltwatertester.html
Wikipedia.org, Wikipedia Foundation Inc., Accessed May 1, 2010. (Source of vocabulary definitions, with some adaptation.) http://wikipedia.org
Juan Ramirez Jr., Carleigh Samson, Stephanie Rivale, Denise W. Carlson
© 2009 by Regents of the University of Colorado.
Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Last modified: May 22, 2015