Here's a quick cheap way to get some hydrogen and oxygen.
Step 1: Gather the items
You will need 2 pencils,a cup,some cardboard,salt,a 9-volt battery,a 9-volt battery connected, and a pencil sharpener.
Step 2: The pencils
Sharpen both ends of both of your pencils.Try to have the graphite in the pencil as long as you can.Then cut the cardboard so it comfortably fits on top of your cup.
Step 3: Setting it up
Fill the cup half full with warm water, Mix about 1 teaspoon of salt into the water.Then wrap some of the wire around one end of both the pencils. Attach the other end to the battery. Then you can push the pencils through the cardboard into the water. You will see bubbles around the tip of the pencil.