
Electrolysis with Pencils and Salt Water
Medium
A 9-volt battery and two pencils can split water into separate gases. The process is called electrolysis.
Sharpen both ends of two pencils. Push them through cardboard set over a glass of salt water. Connect each pencil tip to a battery terminal with wire. Tiny bubbles soon appear around both pencil tips.
Hydrogen gas collects at one pencil. Chlorine gas collects at the other. The salt changes the reaction so chlorine appears instead of oxygen. In industrial electrolysis a different solution produces pure hydrogen and oxygen.
Hypothesis
The hypothesis is that electricity can be used to split water into its two parts: oxygen and hydrogen.
Method & Materials
You will sharpen two pencils, cut cardboard to fit over a glass, push the two pencils into the cardboard, dissolve salt into the warm water, and connect one end of the electrical wire to the positive side of the battery and the other to the black graphite of the pencil.
You will need a 9-volt battery, two regular number 2 pencils, salt, thin cardboard, electrical wire, a small glass, and water.
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See what’s includedResults
When the electricity passes through the water between the electrodes, the water is split into its two parts: oxygen and hydrogen. The hydrogen collects around the cathode and the chlorine gas collects around the anode. However, oxygen is not given off in this experiment.
Why do this project?
This science project is interesting because it demonstrates how electricity can be used to split water into its two parts.
Also Consider
Experiment variations to consider include using different solutions and higher levels of electricity to split the water molecules into hydrogen and oxygen.
Full project details
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