The effect of water salinity on electrolysis
The materials required for this science fair project:
- 2 beakers
- 300ml distilled water
- 300ml sea water
- 2 copper electrodes (either a copper rod, copper bar or copper wire)
- 4 1.5V batteries
- Battery holder
- 4 jumper wires with crocodile clips at both ends
- A digital voltmeter
- An ammeter
- A small light bulb with socket
1. For this experiment, the independent variable is the use of seawater or distilled water. The dependent variable is the amount of current flowing in the circuit as indicated by the bulb lighting up, and the brightness of the bulb. This is measured by using the ammeter to measure the current and observing the light bulb. The constants (control variables) are the battery voltage, light bulb wattage and the amount of electrolyte solution used.
2. Label the beakers as A and B. Fill beaker A with 300ml of distilled water and beaker B with 300ml of salt water.
3. Place both copper electrodes in beaker A. The electrodes must not touch one another. Connect one jumper wire from the battery to one of the copper electrodes. The other wire from the battery is connected through the light bulb and ammeter to the second electrode in the beaker. Once the connection is done, the electrolysis process will begin. Please refer to figure 1 for the circuit connection. The voltage can be measured using the digital voltmeter between the electrodes.
4. Observe the light bulb, ammeter readings and voltmeter readings and record the observations in the table given below.
5. Repeat procedures 3 and 4 using the seawater in beaker B and record the observation and readings in the table below.
1. Use only batteries. NEVER connect to a mains supply.
2. Conduct the experiment under supervision of a qualified person (science teacher). Flammable gasses may be released.
3. Electrolysis of sea water may produce chlorine gas. Take necessary precaution. Ensure that the experiment is conducted in a well-ventilated laboratory