Salt Water & Solar Powered Car - Prof Bunsen

Salt Water & Solar
Powered Car
This small hybrid car can run on direct solar energy or be
powered from an electrochemical cell using salt water as an
electrolyte.
A. Solar mode
Simply place the car on a smooth surface with the solar panel exposed to direct sunlight. The
switch at the bottom should be switched to the right (as viewed from below).
B. Electrochemical mode
Slide the white fuel cell compartment at the back from the car and remove the white cover.
The fuel cell is made up of the following parts:
Black air electrode White Fabric Magnesium electrode
1 1 + 1 spare 1 + 2 spare
Each magnesium electrode can power the car for 3 hours continuously but then needs to be
replaced as the magnesium metal is turned into magnesium ions and will be eroded:
2Mg (s) ➔ Mg 2+ (aq) + 2e -
(oxidation process)
Prepare a salt solution
Dissolve ½ a teaspoon of table salt in ½ a glass of tap water.
Setting-up the fuel cell
1. Keep the sequence of the items in the cell:
1. Black air electrode at bottom
2. White fabric in centre
3. Shiny magnesium electrode at top
1.
3.
2.
Note: The fabric acts as a salt bridge but also as an insulator
to keep the two electrodes separate. Check that the two
electrodes do not make direct contact.
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2. Remove the magnesium electrode and wet the white fabric with four drops of salt solution
using the pipette.
3. Replace the magnesium electrode and then the white cover.
4. Carefully slide the fuel cell back into the car, checking that the two electrode strips
(magnesium and black electrode) slide in below the metal contacts of the car. Do not force
as this may damage the electrodes.
5. Switch the bottom switch to the left (as viewed from below) and run the car on a smooth
surface.
Please Note
• When the car loses power, simply add a few drops of salt water to the exposed fabric at the
back of the car.
• If only stopping the car for short periods of time, you can switch the bottom switch to the
right (solar mode)
BUT
• It is important to clean the fuel cell each time you stop using the car else the
electrochemical cell will keep on producing electricity and shorten the cell’s life.
- Gently rinse the black electrode under tap water. Do not scrub with fingers.
- Wash the magnesium electrode, white fabric and white plastic parts under tap water with
your fingers and dry separately.
Regenerating the electrochemical cell (Optional)
Over time you will find that the magnesium will get a black residue built-up on its surface. You
can scrape this off will a blunt knife or screwdriver (careful!) and then sand the magnesium so
that it is shiny again. Use very fine sand paper. Now refit everything and add the salt water.
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