In this demo, a polyethylene rod is charged by rubbing with wool. The charged rod is then used to bend a stream of water flowing from a tap.
Different substances have different attractions for electrons. When two materials are rubbed together, electrons will leave the substance with the lower attractive force and enter the substance with the higher attractive force. This will result in each substance having a slight positive or negative charge. Water is made up of polar molecules, each containing a negatively charged oxygen end and a positively charged hydrogen end. When a charged rod of material is brought near a thin stream of water, the water will be attracted to the charged rod and the stream of water will bend towards the rod.