Physical Science, New York Edition

THE ART OF NEON

Introduction

In this WebQuest, students do some Internet research on neon signs. They learn about the different noble gases that are used to produce colors in neon signs, and about the chemistry involved in producing those colors. Students find out a little about the discovery of neon and the history of neon signs. Students answer some questions about neon signs based on their Internet research. Finally, students use what they have learned about neon signs and the noble gases to design a piece of neon art.

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Task

While students are doing their Internet research, they will try to answer the set of questions given. Each web site has some of the answers to the questions. For some questions, students will have to read through two or three of the web sites. Students should be encouraged to explore web sites beyond the prompts given, especially the sites showing neon art, as they begin to design their own works of neon art.

Objectives

• Research the chemistry of the noble gases – neon, argon, krypton, xenon, and radon.
  
  
• Describe the chemical changes that occur when electricity passes through noble gases to produce the characteristic colors of neon signs.
  
  
• Identify three ways in which different colors can be produced in neon signs.
  
  
• Design a piece of neon art and identify the gases used to produce the colors used.

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Resources

Students will use the Internet links given to find out all about neon signs. They will learn about the chemistry of the noble gases and how electricity passing through glass tubing filled with these gases causes chemical changes that produce light energy. Students will identify the noble gases most commonly used in neon signs. They will also discover how 150 different colors can be produced through use of different types of glass tubing and combinations of gases. Students will use the information they have gathered to answer the set of questions and design a piece of neon art.

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Time

1 class period for research, answering the set of questions, and designing a piece of neon art

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Process

As students progress through the list of web sites, you may help them to focus on what they need to know to answer the questions given. Students are not expected to become experts in the chemistry of the noble gases. However, if any students wish to spend more time on the chemistry of these gases, you may encourage them to do so. Tell students that although glass tubing can be bent into nearly any shape prior to the insertion of the gases, most often it is sold in lengths of 4, 6, and 8 feet. Their designs should take these lengths into consideration. If students choose unusual colors for their neon art they may have trouble identifying what type of tubing is used for that color.

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Evaluation

You may assign 10 points to each of the eight questions, and 20 points to the design of a neon art piece, for a total of 100 possible points. The answers to the questions are given below. You may rate the answer to each question by the following point scale: Excellent – 9-10 points; Very Good – 7-8 points; Good – 5-6 points; Satisfactory – 3-4 points; Poor – 1-2 points; and Unsatisfactory – 0 points.

Questions about The Art of Neon

1. Neon gas was discovered in 1898 by William Ramsey and Morris Travers. The first neon lamp was produced by Georges Claude.
   
   
2. Neon produces a reddish-orange color. Argon produces a faint purple. Krypton produces a ghostly white. Xenon produces a blue glow. No information exists on radon as it is not used in neon signs.
   
   
3. Neon and a combination of argon and mercury are the most commonly used gases in neon signs.
   
   
4. Neon tubes are capped off by two glass electrodes that have wire passing from outside to inside. One of these electrodes has a tubulation – a small tube which remains as a passage from outside to inside. Tubulations are sealed to a pumping system. The pumping system has glass stopcocks or valves that allow sections to be selectively opened or closed. An ultrahigh vacuum pump pulls air out of the tube while a high voltage transformer bombards and heats the remaining air – to produce temperatures in excess of 500ºF. This allows the tube to achieve a higher degree of purity. When a high vacuum is reached, and the tube begins to cool, a small amount of inert gas is introduced from a flask or a tank of pressurized gas. The tubulation is then heated and as it is pulled it such inward to make the tube’s own seal.
   
   
5. Electrical current bombards the inert gas atoms with electrons, knocking some electrons out of their orbits, thus ionizing the gas atoms. These free electrons collide with other free electrons, sending them back towards the gas atoms. When the free electrons collide with the atoms, they are absorbed into the atoms, thus releasing energy in the form of light.
   
   
6. 1) Clear glass tubing with neon produces red or reddish-orange; Clear glass tubing with argon produces faint purple. 2) Some colors are produced by inert gases in tubing with fluorescent powders painted or baked on the inside. 3) Colored glass may be used in combination with neon or argon and mercury to produce other colors.
   
   
7. Neon signs can last for decades; most last at least 8 to 15 years.
   
   
8. more than 150 colors

Once students have answered the questions, evaluated their designs for neon art pieces. Make sure they have identified the colors used, what gases produce those colors, and the size of the finished piece of art.

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Conclusion

Using information gathered from the Internet, students should be able to answer the questions given about the chemistry of the noble gases and about neon signs. Students should be able to describe the chemical changes that occur as electricity passes through these gases when they are confined within the glass tubing of neon signs. Students should also be able to identify the three ways in which glass tubing is treated to produce a wide variety of colors when combined with neon and argon and mercury. Students should be able to discover that although krypton produces a ghostly white color when electricity is applied, it is too faint to be of use in neon signs.

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