a battery that works with air and saltwater
science project experiment is a simplified version of the air
battery project available at ScienceProject.com. Pictures
and excerpts of information are published here with permission.
|Batteries have been made with many different chemical compounds.
Scientists often try to make batteries that provide more energy and last
longer. Many of such high quality batteries are commercially available
today. They are used in flashlights and electronic devices such as
radios, watches, computers and calculators.
Making a battery is always an exciting science project. Your home
made batteries can be used as chemistry, physics or electricity project.
Click here to see the
instructions for Advanced Kit.
How the battery is made?
A battery is made of two different electrodes inserted in a chemical
compound. A chemical reaction between the electrodes and the chemical
compound produces electricity. For example if you insert a copper rod
and an iron rod in a cup of orange juice, that will be a battery. In
this example copper rod and iron rod are the electrodes and the orange
juice is the chemical compound or electrolyte. The problem is that the
electricity produced by such a battery is too little and has no
practical use and you cannot use it to light up a light bulb. The
saltwater battery described in this project guide can light up a light
bulb for a few seconds. When the light goes off, you can simply empty
the used salt water and add fresh salt water to get light again. By
adding a small amount of hydrogen peroxide you can get more light and
the light will last longer.
List of materials you need:
|This is the minimum
list of material you need for your experiment.
- Miniature light bulb (low
voltage, low current)
- Miniature base for light bulb
- Pair of red insulated copper
wire with alligator clips
- Pair of black insulated copper
wire with alligator clips
- Magnesium Electrodes
- Iron Electrodes
- A cup of saltwater (not
in the picture)
- Screws for the miniature base.
- Hydrogen Peroxide
Additional optional materials you may
- A wooden board to mount the
miniature base (light holder)
- Plastic container about 4" x
4" x 4"
- Hydrogen Peroxide
is a good title for my project?
You can call it
"Air battery", "Salt water battery",
"electricity from air" or "electricity from the
- Loosen the screw on both contacts of
the bulb holder. Clip one end of the red wire to one screw, and clip
one end of the black wire
to the other screw.
- Screw the light bulb on the
- Connect the remaining red alligator clip to
the iron electrode (Steel wool) and secure it on one side of the plastic
container or the cup.
- Connect the remaining black alligator clip to
the magnesium electrode (2 of them) and secure it on the opposite side of the
container. (You may need to hold them by hand or use a small tape to
hold them in place on the side of the container.
- In another pitcher, prepare some
strong, warm salt water. Add enough salt so at the end some salt
will remain at the bottom of the pitcher.
- Transfer the salt water from the
pitcher to the container.
- At this time, if all the connections
are secure and the electrodes are large enough, you should get a
|In this diagram two
magnesium electrodes are used at the same time in order to get a
higher electric current.
In this process magnesium will be
consumed and converted to magnesium hydroxide.
Half of the steel wool is enough for this
How can I get more light?
- Make sure your electrodes are
not touching each other.
- Make sure there is nothing
blocking the space between the electrodes.
- Make sure that the alligator
clips are not touching the salt water.
- Both electrodes must have the
maximum possible surface contact with salt water.
The test tube electrodes (magnesium
electrodes in test tubes) are formed like a spring. This provides the
largest possible surface contact. For Iron electrode you may use steel
wool. Steel wool has a very large surface contact. A steel screen may
work as well.
You may notice that you will get more
light if you stir the solution or if you remove the iron electrode and
insert it back again. Such actions provide oxygen to the surface of the
Note: Steel is about
|The oxygen in the air
may not be enough for your demonstration and you may get a dim
In this case you may add some
oxygen (in the form of hydrogen peroxide) to the salt water. That
should immediately increase the light.
|A cup is relatively
small. If you have access to a larger container, you will get a
better result. In a larger container, it is easier to secure the
electrodes in two opposite sides so they will not touch each
|Where to buy the
The main components of this
project are available as a set in MiniScience.com online store and
KidsLoveKits.com. This set will only include the essential
components. You must have a plastic container, a wooden board,
some iron and some hydrogen peroxide to complete your material.
This set includes 2 Magnesium
electrodes, insulated wire, light bulb, light base, alligator
clips and screws.
produced in this way may be used to light up a light bulb, an LED
or run a low voltage electric motor.
polarity or direction of electricity is especially important when
you are trying to light up an LED.
Each LED has 2 legs.
One is longer than the other. The longer leg must be connected to
the positive pole of the battery or Iron. The shorter leg must be
connected to the negative electrode or Magnesium.
to the list of projects
Does it really work?
Although a saltwater battery is not as strong as a real battery, it
can produce visible light on a low voltage light bulb. It is also safer
than batteries that use many harmful chemicals.
What chemicals do I need?
The only chemical that you need is Sodium Chloride (NaCl) also known
as table salt. This is the chemical that you usually have it at home. If
not, you can buy it from grocery stores. Good quality, pure and
inexpensive packages of salt are often marked as kosher salt. You also
need water (H2O).
What electrodes I can use?
Some articles suggest using Aluminum and Copper metals as electrodes;
however, I have not been able to verify that. I suggest using iron and
magnesium metals. Of course you can test any combinations of metals that
you like. Inexpensive metal electrodes are available at MiniScience.com
Suggested List of material:
1. Salt and water
2. Iron electrode. For best results
use steel wool or steel screens as electrode. High surface area of
steel wool or steel screen will simplify the production of
3. Magnesium electrode
4. Wire lids with alligator clips
5. Miniature light bulb (Low voltage)
6. Miniature base
7. Wooden board to mount the
8. Screws for Miniature base
How does it work? What is the chemical
When Iron and magnesium are placed in
water, multiple chemical reactions happen that contribute to the
movements of electrons from magnesium electrode towards iron
electrode. During these processes Iron electrode oxidizes to Iron
oxide and magnesium electrode reduces to magnesium hydroxide.
Here's what is happening in more
- Magnesium have a tendency to react
with water and form magnesium hydroxide. To do this each magnesium
atom must lose one electron (and become Mg+ ions). While the
magnesium electrode is loosing electrons it will form the negative
- The electrons from the magnesium
atoms combine with the hydrogen ions in the water and form H2
molecules (Hydrogen gas). We see the hydrogen gas as bubbles forming
on the magnesium.
- On the other electrode, the iron
that is oxidized by air and is now in the form of Fe++ ion needs to
receive two electrons to change back to iron. This will create
shortage of electrons in the iron side and make the iron a positive