Electrolysis
Electrolysis is using electricity to break water apart into hydrogen gas and oxygen gas.
Water in a pot is made of tiny pairs — one hydrogen piece bonded to one oxygen piece. When you run electricity through the water, it acts like a wedge that pries those pairs apart. The hydrogen pieces float up to one side and collect as bubbles. The oxygen pieces collect on the other side, each type going to its own spot.
Explaining electrolysis by grade level
When you put two pencils in salt water and connect them to a battery, something happens. Tiny bubbles start forming on each pencil. The electricity from the battery is pulling water apart into two invisible gases. One pencil gets bubbles of hydrogen. The other gets bubbles of oxygen. The water is splitting right in front of you.
Projects that explore electrolysis
Electrolysis splits water with electricity — and voltage controls how fast that splitting happens. When you raise the voltage from 1.5V to 6V, the collection time drops from about 14 minutes down to under 5 minutes.
Electrolysis uses electricity to break water apart, and more batteries mean faster results. More voltage pushes more current through the solution, so the hydrogen gas collects faster each time you add another battery.