What happens when voltage is increased during electrolysis?Featured science projectScience project video

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Complexity level:
Project cost ($):
Time required:
It will take an hour to set up the science experiment, and an hour to conduct it
Material availability:
Easily found at a hobby store.
Safety concerns:

Use only batteries. Do not connect to mains supply.  Conduct the experiment under supervision of a qualified person. Highly flammable gasses will be released. Ensure that protective gear is worn at all times.


This science fair project was performed to investigate the relationship between the DC voltage applied to an electrolyte and the rate of hydrogen gas produced during the process of electrolysis.


Increasing the DC voltage applied to an electrolyte solution will increase the rate of release of hydrogen gas.


Electrolysis process

Electrolysis refers to a chemical process that occurs in an electrolyte solution when an electric current is passed through the solution. An electrolyte solution is made up of negatively charged ions - cations - and positively charged ions - anions. Cations and anions move freely in an electrolyte solution.

The electrolysis process takes place when the positive and negative terminals of a battery are connected to conductors called electrodes and immersed in the electrolyte solution. The electrode connected to the negative terminal is called the cathode and the electrode connected to the positive terminal is called an anode. When the cathode and anode are connected to the battery and immersed in the electrolyte, the negative ions (anions) will be attracted to and move towards the anode (positive electrode). The positive ions (cations) will be attracted to and move towards the cathode (negative electrode).

When the ions reach the surface of the electrodes the following reactions may occur.

  1. Deposits may start to form on the surface of the electrode.
  2. Gasses may be released from the electrodes.
  3. The product of the electrolysis process may be dissolved in the electrolyte solution.

Scientific Terms

Electrolysis, electrolyte, ions, cations, anions, electrodes, anode, cathode


The materials required for this science fair project:
- abeaker
- tap water
- 4 table spoons of salt
- 4 1.5V batteries
- a battery holder
- 2 jumper wire that have crocodile clips at both ends
- 2 test tubes
- 2 PVC insulated copper wires (5mm2) 150mm in length each
- a stop watch
- a pair of pliers
- a black color permanent marker pen


1. For this science fair project, the independent variables are the number of batteries used (ie: the DC voltage applied to the electrolyte). The dependent variable is the time taken to collect the released hydrogen gas. This is measured by using the stopwatch. The constants (control variables) are the amount of the salt content in the electrolyte solution, the amount of oxygen collected in the test tube and the surface area of exposed copper in the electrolyte solution.

2. Strip the insulation of both copper wires exposing approximately 30mm of wire on both ends, using the pliers. Bend the wires into ‘S’ shapes and place them inside the beaker as shown in figure 1 below.

3. Fill the beaker with water and add 1 tablespoon of salt. Dilute the salt in water.

electrolysis science project

4. Draw a line using the permanent marker pen along the circumference of the test tube. The line should be placed at about the center of the test tube. Fill the 2 test tubes with water and place them inverted, inside the beaker as shown in Figure1. The exposed copper wire should be placed entirely within the test tube.

5. The test is started by using one DC1.5V battery. The battery terminals are connected to the copper wire, using the jumper wires. Start the stopwatch. How long does it take for hydrogen to accumulate to the level of the line? Record this time in the table below. Procedures 3 to 5 are repeated using 2 batteries (DC3V), 3 batteries (DC4.5V) and 4 batteries (DC6V).


The results show that increasing the number of batteries ( DC voltage) will result a faster rate of release of gasses.

Voltage applied (V dc)





Time measured (minutes)





The chart below represents the results of our science experiment

electrolysis science fair project


Our hypothesis has been proven to be true. Increasing the DC voltage applied to the electrolyte solution will speed up the release of hydrogen gas.

Electrolysis has many uses. It is used in industrial processes like electroplating as well as in certain measuring devices like the pH meter. Astronauts use electrolysis to produce oxygen in space.

Also consider

This science fair project can be repeated by varying the amount of salt in the water.

This science project may be modified by using different types of electrolytes like vinegar or sulfuric acid.


Electrolysis - http://en.wikipedia.org/wiki/Electrolysis

Electrolysis - http://www.tutorvista.com/content/chemistry/chemistry-iii/redox-reactions/electrolysis.php