For Use with Chapter 3
Matter, Property, and Changes

The Fourth State
Posted November 1st, 2001

If a quiz show host posed the question, "What are the states of matter?", many contestants would correctly answer, "solid, liquid, and gas". But the astute contestant would include in the list another state of matter called plasma.

A plasma is generally defined as a gaseous state of matter in which a part or all of the atoms or molecules are dissociated to form ions. Plasmas consist of a mixture of neutral particles, positive ions, and negative electrons. (Plasmas are often used in a plural sense because they can be composed of ions dissociated from any number of atoms or molecules.) Because plasmas have a gaseous nature, many resources do not classify plasmas as a true state of matter. However, in recent years, plasmas are more frequently being described as the fourth state of matter. One of the reasons that plasmas are often overlooked in discussions of the major states of matter is that plasmas do not occur naturally on earth, except in the form of lightning bolts. But that does not mean that naturally occurring plasmas are rare. In fact, plasmas are a major component of interstellar matter and may actually comprise over 99% of the matter of the universe.

Research and Development

Presently, plasmas are the subject of much research and application development, largely because plasmas carry electrical currents and generate magnetic fields. These characteristics allow plasma to be controlled and used for practical applications. Even a cursory investigation of the current uses of plasmas uncovers a list of familiar applications. For example, did you know that the light emitted from fluorescent bulbs is produced by a plasma. The plasma converts electricity from the wall into a form that causes a phosphor coating (the white coating on the glass tube) to produce light. A short list of applications might include

• high-efficiency plasma arc lighting
  
  
• semiconductors for consumer electronics
  
  
• flat-panel display devices
  
  
• industrial cleaning processes
  
  
• welding and fabrication methods
  
  
• sterilization techniques

Activity

Use the internet to research a current or potential application of plasmas and prepare a brochure that describes the application and its importance to society. Your brochure could describe a commercial application or a theoretical application that could prove beneficial with further development.

References/web sites:

http://www.llnl.gov/das/das_research/plasma.html

http://www.plasmas.org

http://www.pp.ph.ic.ac.uk

http://ojps.aip.org/pop