salt water battery experiment explanation

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Kid Maker How-To: Make a Salt Water Battery

Is your child looking for a science project try this idea for a diy battery..

A battery works when electricity is produced by something called an oxidation/reduction (redox) reaction.  

In this project, you and your child (adult supervision is required) use two different metals and some salty liquid to create a redox reaction.  One metal will oxidize and lose electrons.  The other will reduce and gain electrons in the process. These reactions can result produce toxic chemicals, so use these precautions:

• Wash hands before and after experimenting with batteries and electrolytic cells.
• Experiment only in a well-ventilated space.
• Wear latex or nitrile gloves.
• Do not reuse containers you use in this project for food or other non-science purposes.

Saltwater Battery + Lesson Plan

Introduction: Saltwater Battery + Lesson Plan

Electricity can be very complex, but it doesn't have to be! In fact, it's so simple we can generate electricity with a small cup of saltwater. This project is a great introductory project to electricity and is ideal for middle schoolers all the way to high school seniors. If you're using this in a classroom setting, please view the attached documents for a lesson plan, lab guide, and post lab assignment. The lesson plan is meant for students aged 14-18.

Attachments

For each group, you'll need:

An Eight oz. Plastic Cup

180 mL of Water

30 grams of salt

2 pieces of ten cm. Conductive Wire (Copper works best)

A Multimeter

A stirring rod or spoon

2 Alligator Clips

Optional: Scotch Tape

Step 1: Add Saltwater to the Cup

Begin by making sure your plastic cup is empty and clean. Pour in the water, and add the salt. Using a stirring rod or spoon, gently mix the solution until the salt is fully dissolved.

Step 2: Thread the Wires Through the Alligator Clips

Thread the wire through the holes in the end of the alligator clip. Wrap the wire around the base to ensure that the wire stays in contact with the clip. Do this with both clips.

Step 3: Insert Your Wires

Once the salt has dissolved, insert the wire into your cup of saltwater. The wires shouldn't touch each other and should only come in contact with the water and the cup. If you're struggling making the wires stay apart from one another, tape the wires to the inside of the cup.

Step 4: Attach the Multimeter

Make sure the multimeter is turned on. The multimeter should be set to DCV 20. Attach the red cable to one clip, and the black cable to the other clip.

Step 5: Watch Your Current

Tada! You successfully created a battery and an electrical current! The multimeter should show that there's an electric current flowing through it. Although there isn't much to watch, you will see the display on the multimeter change. If enough of the batteries are joined together they could potentially power a small light.

You can take the experiment further by changing the salt to water ratios and recording which one produces the most voltage, experimenting with different wire materials, or using a fluid other than water.

Please take the time to view the attached documents if you wish to integrate this into a lesson plan.

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Making Electricity From Salt Water

How to Build a Homemade Battery

Saltwater can serve as the electrolyte in a battery, generating electricity. A battery has three parts: an electrolyte and two electrodes, which are made of different materials, often metals. Some of the first batteries, made by Alessandro Volta around 1880, used saltwater, silver and zinc to generate electricity. This type of battery is easy to build and experiment with.

Electrolytes and Batteries

In water, table salt, or sodium chloride (NaCl), dissolves into positively charged sodium ions (Na+) and negatively charged chlorine ions (Cl-). Chemists call a solution of ions such as this an electrolyte. In a battery, one electrode, called the cathode, sheds electrons into the solution, leaving it with a positive charge. At the same time, the other electrode, the anode, collects electrons, giving it a negative charge. Ions in the electrolyte help facilitate this process. The charge imbalance between the two electrodes creates a electrical potential difference, or voltage. If you connect the terminals in a circuit, the electrons built up in the anode will flow through the circuit back to the cathode, creating an electrical current.

Your Own Voltaic Pile

Volta made his "Voltaic Pile" battery with units consisting of saltwater-soaked paper sandwiched between a silver disk and a zinc disk. He stacked up this basic unit to create a battery with significant voltage. The term for such basic units is cells. You can make a similar battery quite easily with household items. You will need five pennies made after 1982, cardstock or paperboard, salt, water, electrical tape, 120-grit sandpaper and two wires with stripped ends. Pennies made in 1983 and after are copper-coated zinc disks. Thanks to this fact, we don’t need two different types of metal disks as Volta did.

Building the Battery

Sand one side of four of the pennies all the way down to a flat zinc surface. Dissolve one tablespoon of salt in one cup of water (heating helps). From the cardstock, cut out four disks roughly the size of the pennies, and soak them in the salt water. Place one penny copper side down on the table and place a soaked disk on top of it. Continue stacking by alternating pennies and soaked disks, with the intact penny on top of the last soaked disk. Holding one wire on the first coin and one on the last coin, wrap electrical tape around the assembly to hold it together. Sealing the entire unit with tape will inhibit evaporation, making the battery last longer.

Using the Battery

Each cell, consisting of the zinc side of one penny, a soaked disk and the copper side of another penny, generates around one volt. With four cells, your battery will generate roughly four volts. You can test this with a multimeter. Also, four volts is enough to make an LED shine brightly. Connect the short lead from the LED to the end of the battery that has the intact penny. This is the anode -- the negative pole of the battery.

Further Experiments

Almost any combination of two different metals for the electrodes will make a battery. Different combinations yield different voltages. You can make a battery similar to Volta’s by stacking up cells made of saltwater-soaked cardstock sandwiched between two different metals. Ideas include pennies and nickels, pennies and aluminum (foil or sanded pieces of pop cans), pennies and zinc-coated washers, and uncoated steel washers and aluminum.

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About the Author

Ariel Balter started out writing, editing and typesetting, changed gears for a stint in the building trades, then returned to school and earned a PhD in physics. Since that time, Balter has been a professional scientist and teacher. He has a vast area of expertise including cooking, organic gardening, green living, green building trades and many areas of science and technology.

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