Science Projects Index
Take a vessel full of hot water. Dissolve alum in it to the maximum possible. Now take a pencil and tie a small piece of thread to it.
Place the pencil on top of the vessel in such a way that the thread touches the water. Keep it like that for a few days.
You will see a crystal forming on the end of the thread. And it keeps on growing if left for a few days.
Take a cardboard and make two holes in it. Then insert two iron nails into the two holes. Place the cardboard on top of a glass tumbler full of salt water in such a way that the nails are immersed in the water. Connect the top ends of the nails to the two terminals of a battery. Once the circuit is established, you will find air bubbles collecting around the nails. If you observe after some hours, you will find that the nail connected to the positive terminal of the battery is coated with rust. That is iron oxide.