Expt 011 -- Glowing Tubes

Description

The gas in a Tygon tube glows from the electric energy of a Tesla Coil. A plastic syringe is used to pull the vacuum. Glowing effects are possible by changing the path of the tubing.

Chemical Concepts

  1. One form of energy may be changed to another form of energy. For example, electrical energy may be changed to heat or light energy.
  2. If atoms or molecules are close together, electrical energy is frequently changed to thermal energy. Molecules bump one another and vibrate.
  3. If atoms or molecules are farther apart as in a gas at low pressure, the electrons in atoms or molecules may be excited by the electrical energy. The electrons emit light when the electrons move back to their normal state.

Safety

Be certain that the Tesla Coil is grounded and that your hands are dry.

Procedure

If you are lucky enough to have a strong vacuum pump, you may substitute the pump for the syringe in this experiment.

  1. Coil the tubing around an object with smooth bends. A large flask works well. Tape in place with clear tape.
  2. Insert the tip of the Tesla Coil into one end of the tubing. Push the tubing firmly against the tip to make a seal.
  3. Attach a large plastic syringe (or vacuum pump) to the other end of the tubing. Check to be sure the fitting is tight. If the tubing fits too loosely, you need to cut off the end or use a smaller sized tubing (inside diameter smaller). You must stretch the tubing as you connect it or the connection leaks too much.
    !!!Click here to See Picture.
  4. Darken the room. Turn on the Tesla Coil. Pull a vacuum with the syringe. Observe. It takes a moment or two for the pressure to drop enough. A strong arm on the syringe helps so you may wish to enlist a student to pull the syringe. The student help frees you to manage the Tesla coil and the other students.
    !!!Click here to See Movie.
    If you have a problem, secure both ends of the tubing, and try again. The problems are usually leaks at the connections. The plastic syringes do pull a tight enough vacuum.

Questions

  1. How do fluorescent lights work?
  2. Which elements or ions might be emitting light in the tube?

Handout Makeup

Name ___________________________ Class _______

Teacher __________________________

BeckerDemos 011 Glowing Tubes

Watch the movies.

Describe the demonstration. Answer the questions.

Curriculum-

This experiment fits in when studying different forms of energy or when studying atomic structure. The demonstration may lead to discussing electronic energy levels in atoms and molecules.

Activity-

Demonstration - Teacher Only

This works well as a teacher demonstration followed by discussion of energy transformations or electronic energy levels.

Safety-

Be certain that the Tesla Coil is grounded and your hands are dry.

Time-

Teacher Preparation: 5 minutes

Class Time: 5-20 minutes The variable time is for discussion of the experiment.

Materials-

Answers-

Q1. How do fluorescent lights work?
A1. A small amount of gas in the tube is excited by an electric arc. The gas glows at distinct energies (colors) as the electrons in the atoms decay to the stable state. Subsequent excitation of a solid state phosphor coating on the inside of the lamp results in a glow with a continuum of wavelengths. (The gas in the lights is mercury. Mercury lines are evident when measured with a spectroscope.)
Q2. Which elements or molecules might be emitting light in the tube in this experiment?
A2. Air is left behind. Argon, nitrogen, and oxygen are the most abundant. Students have no way to distinguish which substance is glowing.

Key Words 1-

electrical energy, energy, light energy, energy level