Understanding simple batteries
- Two each copper and zinc rods about 5 to 10 cm (2 to 4″) long and 3 mm (1/8″) in diameter
- One each aluminum, brass and stainless steel rods of the same size
- Plastic vials or test-tubes with two holes cut in the lid to fit the metal rods
- A test-tube holder
- 1/8 cup each diluted vinegar, salt water, soda and water (or other household liquids)
- A digital multimeter
When two metal rods are placed in vial with a liquid in it, a voltage can be measured between the rods (the combination acts as a battery). The liquids are called electrolytes. The rods are called electrodes. The chemical reaction is similar to that which occurs in a commercial battery. A battery with a liquid electrolyte is often referred to as a “wet cell.”
- Place the vial or test tube in the holder. Add one of the liquids to the vial, and place and one copper and one zinc rod in the vial so they do not touch each other, but are in the liquid.
Measure the voltage between the rods. How much is it?
- Design and conduct an experiment to determine the effect of different liquids (used as electrolytes) on the voltage produced in a liquid battery.
- Your experimental question is:
- State your hypothesis:
- Define your independent variable (IV):
- Define your dependent variable (DV):
- What factors were held constant in your experiment?
- Design a data table. Conduct your experiment and record your data.
- Graph your data.
- Conclusions: What conclusions can you draw from the experiment you just conducted?
- Discussion: The best electrolyte you used produced about 1V. How do you think a 6V battery is made? Or a 9V or 12V?
- From this lab, what conclusions can you draw about how different electrolytes affect the voltage produced by a battery?
- If you have not done the veggie battery lab yet, what do you think would happen if you used the liquid that produced the highest voltage, and tried out different combinations of rods for electrodes?
Gather your data in the table below:
|One copper rod and one rod of the following metal:||Voltage produced (V)||One zinc rod and one rod of the following metal:||Voltage produced (V)|
What conclusions can you draw from using different combinations of electrodes?