How to Build an Oxygen Generator

Making oxygen for commercial or medical use requires a great deal of equipment. But it's easy and safe to make a oxygen generator as a science experiment. Oxygen (along with hydrogen) is one of the elements that make up water. You can use electricity in a process called electrolysis to make an oxygen generator by separating the oxygen and hydrogen in water.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Water
• Table salt (sodium chloride)
• 2 copper wires abut 3 feet in length
• 2 test tubes
• 4 small alligator clips
• 2 test tube clamps
• 2-liter water container (large enough to submerge the test tubes)
• 12 volt battery

1. Place about 225 g (1/2 lb.) of table salt in the empty water container and fill with warm water. Stir until the salt is completely dissolved. You will be passing an electric current through the water. However, pure water is a poor conductor, and the salt improves the conductivity.

2. Strip 3 inches of insulation (if there's any) off both ends of each wire. Wind one end of each wire to an alligator clip so the bare copper is in firm contact with the metal part of the clip. Attach the other end of each wire to the side of the water container with an alligator clip so the exposed copper is in the water. Make sure the two wires are not touching.

3. Attach the other ends of the wires to the battery, one to each terminal. Look at the copper wires in the water. You will see bubbles form on each wire. Those on the wire attached to the positive terminal of the battery are oxygen bubbles; the bubbles on the negative terminal wire are hydrogen.

4. Accumulate oxygen and hydrogen in the test tubes. Remove the wires from the battery, then transfer the other rends of the wires from the sides of the water container to the test tubes so that the exposed copper is inside the test tube, and use alligator clips to hold the wires in place.

5. Fill the test tubes with some of the salt water and place them in the water with their open ends pointing down and under the surface. Use the test tube clamps to fasten the test tubes in place. Make sure there are no air bubbles trapped in the test tubes and that the open ends stay submerged.

6. Connect the other ends of the wires to the battery terminals as before. The bubbles will be trapped inside the test tubes. As the gasses accumulate, you'll notice the test tube containing oxygen has only half the volume of gas as the tube with the hydrogen. The chemical formula for water is H2O. Pure oxygen and hydrogen each form molecules with two atoms (O2 and H2), but you start with twice as many atoms of hydrogen, so the hydrogen gas takes up twice as much volume in its test tube.

Tips & Warnings

• For best results, use a 12-volt battery. A smaller one will work, but will take longer. Do not use house current--that much electrical current in water is dangerous.
• This is an extremely safe experiment. However, it does involve the use of electricity, so there should be an adult present to supervise younger children performing this experiment.

Resources

• Electrolysis