Chapter 7: Electron Transfer Science 9

ELECTRON TRANSFER After you have completed this chapter you will able to: Explain with words and illustrations, the transfer of static charges. Describe the types of static charges State the three laws of static charge Explain how the amount of charge and distance of separation affects the force between them.

Section 7.1: Static Electricity Name some devices that are related to the word electricity Van de Graaf generator lights Computers cell phones fridges Playstation projector television toaster iPods heaters

Static Charge DISCUSS WITH YOUR NEIGHBOUR… What is a static charge? A static charge is an electric charge that can be collected and held in one place What does the word static mean? Static means fixed or not-moving In other words, a static charge is an electrical charge that cannot move.

Examples from everyday life of static... Rubbing your feet on a carpet clothes out of the dryer Lightning sticking a balloon to a wall Combing your hair (especially long hair)

If you recall, matter is made up of atoms and consists of three (3) different kinds of particles: protons, neutrons, electrons. Protons are positively (+) charged, neutrons are neutral (0) in charge and electrons are negatively (-) charged. When the number of protons equals the number of electrons, the atom is uncharged or neutral.

This table should look familiar.... Name Symbol Relative Mass Electric Charge Location in Atom (-) Negative p+ Neutron

This table should look familiar.... Name Symbol Relative Mass Electric Charge Location in Atom Electron e- 0.0005 (-) Negative Orbitals Proton p+ 1 (+) Positive Nucleus Neutron n0 ~1 Neutral

How do all solid materials become charged? The solid must gain or lose electrons! Remember, electrons are the only sub-atomic particles that can leave the atom! If an electron is removed from a neutral atom, the atom has a positive charge. If an electron is added, then the atom will have a negative charge.

Now... Chat with your neighbour Fill in the boxes on your notes sheets with (+) and (-) signs to indicate A neutral object A positively charged object A negatively charged object Neutral objects become positively or negatively charged when they lose or gain electrons, respectively.

Another word for movement when talking bout electrons is electron transfer. A common way for electrons to be transferred is by friction; the process by which two objects are rubbed against one another. This is the process for electrons to be transferred from one object to another.

Insulators and Conductors Insulators: Objects that do not allow electrons to move freely or to be transferred (e.g. Non-metals). Conductors: Objects that allow electrons to move freely and be easily transferred (e.g. Metals).

Diagramming insulators and conductors Chat with your neighbour and see if you can use (+) and (-) signs to draw an insulator and a conductor.

Graphite (pencil lead) Salt water Insulators Conductors Rubber Glass Wood NON-METALS METALS Graphite (pencil lead) Salt water Q: Can pure water conduct electricity?

Since static electricity is a charge that is held, only insulators can retain a static charge. NOW: Chat with your neighbour and explain why conductors cannot hold a static charge.

The unit for electric charge is called the coulomb (C) named after the physicist Augistin de Coulomb. It takes the addition or removal of 6.25 X 1018 electrons to produce 1C of charge. That’s 6 250 000 000 000 000 000

Static electricity can be dangerous Static electricity can be dangerous. Static electricity can cause sparks that could start fires or explosions. In order to prevent this from occurring objects need to be grounded. Grounding an object involves using a conductor conducted to a large object where electrons can flow in a controlled manner. Usually the earth is used for grounding, hence the name.

What possible uses could there be for static electricity? Chat with your neighbour and see what you can come up with! Plastic Wrap Air Filters Powder coating (painting)

The Van de Graaf Generator!!!! The Van de Graaf generator, invented in 1929 by Robert Van de Graaf, was the first machine that could produce large amounts of static electricity. The machine uses friction between a moving belt at the base of the machine and creates a positive static charge in the metal dome.