• Visit
    • Calendar
    • After Dark Thursdays
    • Buy Tickets
    • Exhibits
    • Museum Galleries
    • Artworks on View
    • Hours
    • Getting Here
    • Visitor FAQ
    • Event Rentals
    • Field Trips
  • Education
    • Professional Development Programs
    • Free Educator Workshops
    • Tools for Teaching and Learning
    • Learning About Learning
    • Community Programs
    • Educator Newsletter
  • Explore
    • Browse by Subject
    • Activities
    • Video
    • Exhibits
    • Apps
    • Blogs
    • Websites
  • About Us
    • Our Story
    • Partnerships
    • Global Collaborations
    • Explore Our Reach
    • Arts at the Exploratorium
    • Contact Us
  • Join + Support
    • Donate Today!
    • Membership
    • Join Our Donor Community
    • Engage Your Business
    • Attend a Fundraiser
    • Explore Our Reach
    • Thank You to Our Supporters
    • Donor & Corporate Member FAQ
    • Host Your Event
    • Volunteer
  • Store
  • Visit
    • Frequently Asked Questions
    • Calendar
      • Today
      • This Week
      • Online
      • After Dark Thursday Nights
      • Arts
      • Conferences
      • Cinema Arts
      • Free + Community Events
      • Fundraising Events
      • Kids + Families
      • Members
      • Special Hours
      • Private Event Closures
    • Prices
    • Hours
    • Getting Here
    • Museum Map
    • Free Admission and Reduced Admission
    • Accessibility
    • Tips for Visiting with Kids
    • How to Exploratorium
    • Exhibits
    • Tactile Dome
    • Artworks on View
    • Cinema Arts
    • Kanbar Forum
    • Black Box
    • Museum Galleries
      • Bernard and Barbro Osher Gallery 1: Human Phenomena
        • Tactile Dome
          • 1971 Press Release
        • Black Box
        • Curator Statement
      • Gallery 2: Tinkering
        • Curator Statement
      • Bechtel Gallery 3: Seeing & Reflections
        • Curator Statement
      • Gordon and Betty Moore Gallery 4: Living Systems
        • Curator Statement
      • Gallery 5: Outdoor Exhibits
        • Curator Statement
      • Fisher Bay Observatory Gallery 6: Observing Landscapes
        • Wired Pier Environmental Field Station
        • Curator Statement
    • Restaurant & Café
    • School Field Trips
      • Getting Here
        • Bus Routes for Field Trips and Other Groups
      • Admission and Tickets
      • Planning Guide
      • Reservations
        • Field Trip Request Form
      • Resources
    • Event Rentals
      • Full Facility & Gallery Bundles
      • Fisher Bay Observatory Gallery & Terrace
      • Moore East Gallery
      • Bechtel Central Gallery & Outdoor Gallery
      • Osher West Gallery
      • Kanbar Forum

      • Weddings
      • Proms and School Events
      • Daytime Meetings, Events, & Filmings

      • Rentals FAQ
      • Event Planning Resources
      • Rental Request Form
      • Download Brochure (pdf)
    • Groups / Tour Operators
      • Group Visit Request Form
    • Exploratorium Store
    • Contact Us
  • Education
    • Black Teachers and Students Matter
    • Professional Development Programs
      • Free Educator Workshops
      • Professional Learning Partnerships
      • Teacher Institute
        • About the Teacher Institute
        • Summer Institute for Teachers
        • Teacher Induction Program
        • Leadership Program
        • Teacher Institute Research
        • CA NGSS STEM Conferences
          • NGSS STEM Conference 2020
        • Science Snacks
          • Browse by Subject
          • Special Collections
          • Science Snacks A-Z
          • NGSS Planning Tools
          • Frequently Asked Questions
        • Digital Teaching Boxes
        • Meet the Teacher Institute Staff
        • Resources for Supporting Science Teachers
      • Institute for Inquiry
        • What Is Inquiry?
        • Watch and Do Science
        • Inquiry-based Science and English Language Development
          • Educators Guide
            • Conceptual Overview
              • Science Talk
              • Science Writing
            • Classroom Video Gallery
              • Magnet Investigation
              • Snail Investigation
            • Teacher Professional Development
            • Project Studies
            • Acknowledgments
          • Conference: Exploring Science and English Language Development
            • Interviews with Participants
            • Plenary Sessions
            • Synthesis, Documentation, and Resources
        • Workshops
          • Participant Portal
          • Fundamentals of Inquiry
            • Summary Schedule
          • BaySci Science Champions Academy
          • Facilitators Guides
          • Commissioned Workshops
        • Resource Library
        • Meet the IFI Staff
      • Resources for California Educators
      • K-12 Science Leader Network
      • Resources for Supporting Science Teachers
      • Field Trip Explainer Program
      • Cambio
    • Tools for Teaching and Learning
      • Learning Toolbox
      • Science Snacks
      • Digital Teaching Boxes
      • Science Activities
      • Tinkering Projects
      • Recursos gratuitos para aprender ciencias
      • Videos
      • Exhibits
      • Publications
      • Apps
      • Educator Newsletter
      • Exploratorium Websites
    • Educator Newsletter
    • Advancing Ideas about Learning
      • Visitor Research and Evaluation
        • What we do
        • Reports & Publications
        • Projects
        • Who we are
      • Center for Informal Learning in Schools
    • Community Programs
      • High School Explainer Program
      • Xtech
      • Community Educational Engagement
      • California Tinkering Afterschool Network
        • About
        • Partners
        • Resources
        • News & Updates
        • Further Reading
  • Explore
    • Browse by Subject
      • Arts
      • Astronomy & Space Sciences
        • Planetary Science
        • Space Exploration
      • Biology
        • Anatomy & Physiology
        • Ecology
        • Evolution
        • Genetics
        • Molecular & Cellular Biology
        • Neuroscience
      • Chemistry
        • Combining Matter
        • Food & Cooking
        • Materials & Matter
        • States of Matter
      • Data
        • Data Collection & Analysis
        • Modeling & Simulations
        • Visualization
      • Earth Science
        • Atmosphere
        • Geology
        • Oceans & Water
      • Engineering & Technology
        • Design & Tinkering
        • Real-World Problems & Solutions
      • Environmental Science
        • Global Systems & Cycles
        • Human Impacts
      • History
      • Mathematics
      • Nature of Science
        • Measurement
        • Science as a Process
        • Size & Scale
        • Time
      • Perception
        • Light, Color & Seeing
        • Listening & Hearing
        • Optical Illusions
        • Scent, Smell & Taste
        • Tactile & Touch
      • Physics
        • Electricity & Magnetism
        • Energy
        • Heat & Temperature
        • Light
        • Mechanics
        • Quantum
        • Sound
        • Waves
      • Social Science
        • Culture
        • Language
        • Psychology
        • Sociology
    • Browse by Content Type
      • Activities
      • Blogs
        • Spectrum
          • Arts
          • Behind the Scenes
          • News
          • Education
          • Community & Collaborations
          • Science
        • Eclipse
        • Studio for Public Spaces
        • Tangents
        • Resonance See & Hear Blog
        • Fabricated Realities
        • Tinkering Studio: Sketchpad
        • Exploratorium on Tumblr
      • Exhibits
      • Video
      • Websites
      • Apps
        • Total Solar Eclipse
  • About Us
    • Our Story
    • Land Acknowledgment
    • Explore Our Reach
    • Impact Report
    • Awards
    • Our History
      • 50 Years 1969–2019

    • Senior Leadership
    • Board of Trustees
    • Board of Trustees Alumni
    • Staff Scientists
    • Staff Artists

    • Arts at the Exploratorium
      • Artworks on View
      • Artist-in-Residence Program
      • Cinema Arts
        • History and Collection
        • Cinema Artists-in-Residence
        • Resources and Collaborating Organizations
        • Kanbar Forum
      • Center for Art & Inquiry
        • Begin Here
          • Lessons
            • Bob Miller/Light Walk
            • Ruth Asawa/Milk Carton Sculpture
          • Workshops
      • Resonance
        • About the Series
        • See & Hear
        • Past Seasons
      • Over the Water
      • Black Box
      • Upcoming Events
      • Temporary Exhibitions
      • Arts Program Staff
    • Teacher Institute
    • Institute for Inquiry
    • Explainer Programs
    • Studio for Public Spaces
    • Exhibit Making
    • Partnerships
      • Building Global Connections
        • Global Collaborations
          • Projects
          • Approach
          • People
          • Impact
      • Partnering with Science Agencies
        • NASA
        • NOAA
      • Partnering with Educational Institutions
      • Osher Fellows

    • Job Opportunities
    • Become a Volunteer

    • Contact Info
    • Newsletter
    • Educator Newsletter
    • Blogs
    • Follow & Share
    • Press Office

    • FY21 Audit Report
    • 990 FY20 Tax Return
    • Use Policy
      • Privacy Policy
      • Intellectual Property Policy
  • Join + Support
    • Donate Today!
    • Membership
      • Membership FAQ
      • Member Benefits
      • After Dark Membership
      • Member Events
      • May Is for Members
    • Join Our Donor Community
    • Engage Your Business
      • Corporate Membership
      • Luminary Partnerships
    • Attend a Fundraiser
      • Wonder Funday
      • Science of Cocktails
      • Party at the Piers
        • Event Leadership and Host Committee
    • Explore Our Reach
    • Thank You to Our Supporters
    • Donor & Corporate Member FAQ
    • Volunteer
      • How to Apply
      • Application for Internships
      • Our Contract
      • Application for Individuals
  • Press Office
    • Press Releases
    • News Coverage
    • Events Calendar
    • Photographs
    • Press Video
    • Press Kits
    • Press Visits
    • Exploratorium Logos
    • Recent Awards
    • Praise for the Exploratorium
    • Join Our Press List
  • Store

Masks and vaccinations are recommended. Plan your visit  

Visitor FAQ Buy Tickets Donate Today
Exploratorium
Exploratorium
  • Visit
    • Calendar
    • After Dark Thursdays
    • Buy Tickets
    • Exhibits
    • Museum Galleries
    • Artworks on View
    • Hours
    • Getting Here
    • Visitor FAQ
    • Event Rentals
    • Field Trips
  • Education
    • Professional Development Programs
    • Free Educator Workshops
    • Tools for Teaching and Learning
    • Learning About Learning
    • Community Programs
    • Educator Newsletter
  • Explore
    • Browse by Subject
    • Activities
    • Video
    • Exhibits
    • Apps
    • Blogs
    • Websites
  • About Us
    • Our Story
    • Partnerships
    • Global Collaborations
    • Explore Our Reach
    • Arts at the Exploratorium
    • Contact Us
  • Join + Support
    • Donate Today!
    • Membership
    • Join Our Donor Community
    • Engage Your Business
    • Attend a Fundraiser
    • Explore Our Reach
    • Thank You to Our Supporters
    • Donor & Corporate Member FAQ
    • Host Your Event
    • Volunteer
  • Store
Science Snacks
Science activity to make a simple battery that will light an LED

Saltwater Pentacell

Explore current events in electrochemistry.

Make your own battery! Create five simple cells from aluminum foil, copper wire, and saltwater, and connect them in series. Together, they produce enough voltage to light an LED.


Grade Bands: 
3-5
6-8
9-12
Subject: 
Chemistry
Materials & Matter
Combining Matter
Physics
Electricity & Magnetism
Energy
Keywords: 
battery
electrode
electrochemistry
ion
electron
current
voltage
salt
aluminum foil
copper
NGSS and EP&Cs: 
PS
PS1
PS2
PS3
CCCs
Scale, Proportion, and Quantity
Energy And Matter
Structure and Function

  • Facebook logo
  • Reddit logo
  • Twitter logo


Tools and Materials

  • Insulated stranded copper wire, 18 or 20 gauge, that can be cut into five 4-inch (10 cm) pieces. Ordinary lamp cord works well—the two conductors of a 12-inch (30 cm) piece can be pulled apart, and you can then cut three 4-inch (10 cm) pieces from one of them and two from the other.
  • Ruler or measuring tape
  • Wire strippers
  • Scissors
  • About 8 inches (20 cm) of aluminum foil from a normal 12-inch-wide (30 cm) roll
  • Pitcher or bowl with a spout
  • About 1 quart (1 L) of water (not pictured)
  • About 2 tablespoons (30 mL) of table salt (sodium chloride)
  • Stirring spoon
  • Five plastic cups
  • Six alligator-clip leads about 12 inches long (exact length not critical)
  • Red light-emitting diode (LED)
  • About 1 tablespoon (15 mL) of vinegar (acetic acid)
  • Measuring spoons

Assembly

  1. Cut the stranded copper wire into five sections of 4 inches (10 cm) each. Strip 2 inches (5 cm) of insulation off one end of each of the five pieces, and then strip 1 inch (2.5 cm) of insulation off the other end of each piece. This will leave a 1-inch (2.5 cm) sleeve of insulation holding the bundle of fine wires together. Twist the strands at the 1-inch (2.5 cm) end of each piece tightly together. Then separate the strands of each 2-inch (5 cm) end so the loose strands look something like a broom (see photo below). These are your copper electrodes.
  2. Cut five pieces of aluminum foil, each about 4 x 4 inches (10 x 10 cm) square. Fold each piece in half, and then in half again, parallel to the first fold, so that the foil square ends up four layers thick, with final dimensions approximately 1 x 4 inches (2.5 x 10 cm). These are your aluminum electrodes.
  3. Add the salt to the water and stir. This is the electrolyte solution—a liquid that can conduct electricity.
  4. Fill each plastic cup about three-quarters full of the electrolyte solution. Then put one aluminum electrode and one copper electrode in each cup. The broomlike end of the copper electrode should be in the solution.
  5. Each cup and its electrodes make up one saltwater cell. Connect the cells in series by clipping alligator-clip leads from the copper electrode of one cup to the aluminum electrode of the next cup, and so on, until all five cells are connected (see photo above). As you attach each alligator clip to an electrode, you can simultaneously clip the electrode to the top of the cup to hold it in place, as shown in the photo below. At the end of the series, the aluminum electrode in the first cup and the copper electrode in the fifth cup should be left unconnected.
  6. Adjust the two electrodes inside each cup as necessary to make sure that they don’t touch each other.

To Do and Notice

Use alligator-clip leads to connect the aluminum electrode in the first cup to one leg of the LED, and the copper electrode in the fifth cup to the other leg.

Did the LED light up? Sometimes you have to look directly into the end of an LED to tell if it’s on. If you’re in doubt, darken the room or cup your hands around the LED to block the ambient light.

If the LED isn’t lit, reverse the legs. (A diode—in this case a light-emitting diode, or LED—allows current to flow only in one direction. If it’s connected “backwards,” it won’t light.)

If the LED still doesn’t light, try adding 1/2 teaspoon (2.5 mL) of vinegar to each cup and stirring. The acidity of water varies from place to place, and if your water is not acidic enough, the vinegar may make a difference. If your water is already acidic enough, you probably won’t need to use the vinegar.

After the LED is lit with five cells, try using four cells. If it lights, then try using three cells. What is the smallest number of cells that will do the job?


What's Going On?

Each cup, with its electrodes and electrolyte solution, is a simple electrochemical cell. The two electrodes are made of dissimilar materials (in this case, two different metals) with different chemical activities. A tug-of-war for electrons occurs between the two electrodes, resulting in a potential difference, or voltage. In the cells you’ve made, aluminum is the more active metal—atoms of aluminum lose their electrons more easily than do atoms of copper. The potential difference causes electrons lost by the atoms in the aluminum electrode to travel through the LED to the copper electrode, and this flow of electrons is the electric current that lights the LED.

If this flow of electrons continued, and nothing else happened, then fairly quickly there would be a buildup of electrons on the copper electrode and a shortage of electrons on the aluminum electrode.

Because electrons have a negative charge, this would result in the copper electrode becoming negatively charged and the aluminum electrode becoming positively charged. Additional electrons that tried to move from the aluminum to the copper would be repelled by the copper and attracted back to the aluminum, and electron flow would stop.

This is where the saltwater electrolyte solution comes into play. Table salt is sodium chloride, and when it’s dissolved in water, it forms positive sodium ions and negative chloride ions. The positive sodium ions are attracted to the negative copper electrode, where they participate in neutralizing the extra negative charge through chemical reactions. Likewise, the negative chloride ions are attracted to the positive aluminum electrode, where they participate in neutralizing the extra positive charge. Therefore, there’s a constant flow of charge from one electrode through the LED to the other electrode, and then through the electrolyte solution, forming a complete circuit.

The five cells make up a battery when they’re connected in series. (A battery is two or more electric cells that are joined together.) The five-cell battery has five times the voltage of each individual cell.

It takes a minimum voltage to light an LED. If you don’t have enough cells, you won’t provide the necessary voltage.

In any electrochemical cell, the greater the difference in the activity of the two materials making up the electrodes, the greater the strength (voltage) of the cell. Since chemical reactions are taking place at the electrodes, the larger the area of the electrodes, the greater the number of electrons that can be pulled per second, and the larger the current (measured in amperes, or amps).

The big idea here is the difference in the abilities of two materials to lose and gain electrons. This same idea is at the heart of the wide variety of batteries used for everything from flashlights to cell phones. The materials, size, and shape of these batteries may differ from those of this saltwater pentacell, but the general principle remains the same.


Going Further

A solid choice?

Why does this Snack use stranded wire with the wires spread apart? Try substituting a piece of 18- or 20-gauge solid copper wire. Do you get the same results?

Metals are not created equal

Try using other metals for electrodes. Can you find metals that will allow you to light the LED using fewer cells? Galvanized nails can be used for zinc, regular iron nails for iron, old silverware for silver, and brass hardware for brass. (A commonly available non-metallic material that can also act as an electrode is carbon pencil lead.)

Measure it

If you have an electrical meter available, try making quantitative measurements of voltage and current for different combinations of metals.

Make a buzz

Try substituting a 1- to 3-volt piezoelectric buzzer for the LED.


Resources

We were introduced to this Snack by Art Morrill.

Shakashiri, Bassam. Chemical Demonstrations: A Handbook for Teachers of Chemistry, Vol. 4. Madison: University of Wisconsin Press, 1992. See pages. 91–95 for a general discussion of batteries.



Related Snacks

Science activity that demonstrates the chemistry of batteries
Aluminum-Air Battery

Construct a simple battery that can power a light.

Science activity that demonstrates charge in a battery
Hand Battery

Use your skin and different metals to create a battery.

Science activity that demonstrates the chemistry of a battery
Penny Battery

Light an LED with five cents.



Creative Commons License



This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Attribution: Exploratorium Teacher Institute

  • Education
    • Teacher Institute
    • Tools for Teaching and Learning
      • Science Snacks
        • Browse by Subject
        • Special Collections
        • Science Snacks A-Z
        • NGSS Planning Tools
        • Frequently Asked Questions



Connect with us!



  •   Sign up for our educator newsletter

  •   Follow #ExploEDU

  •   Teacher Institute YouTube

  •   Teacher Institute Facebook

  •  teacherinstitute @exploratorium.edu

Exploratorium
Visit
Join
Give

Pier 15
(Embarcadero at Green Street)
San Francisco, CA 94111
415.528.4444

Contact Us

  • Plan Your Visit
  • Calendar
  • Buy Tickets
  • Getting Here
  • Store
  • Event Rentals
  • About Us
  • Become a Member
  • Donate
  • Jobs
  • Volunteer
  • Press Office
  • Land Acknowledgment

Get at-home activities and learning tools delivered straight to your inbox

The Exploratorium is a 501(c)(3) nonprofit organization. Our tax ID #: 94-1696494
© 2023 Exploratorium | Terms of Service | Privacy Policy | Your California Privacy Rights |