Category Archives: Kinetic Theory

Diffusion in Air/Water

Demo: TH-D-DA
Pira Index: 4D 50.10

 Lab Equipment  Directions
  1.  closed jar containing Pinesol (inside cardboard tube to disguise it)
  2. large plastic jar with water
  3. blue or green food coloring
  1.  Set jar with water on the desk. Let all the liquid motion settle down. While waiting, open the cardboard wrapped jar.
  2. Ask students to raise their hand as the class proceeds when they smell the chemical.
  3. With minor disturbance, put a couple of drops of food coloring in the water and observe.

Note – it is best to do this near the beginning of the lecture and check with students off and on during the period.

Kinetic Theory (Pasco)

Demo: TH-D-KP
Pira Index: 4D 30.20

 Lab Equipment  Directions
  1. Pasco mechanical vibrator
  2. Molecular motion demonstrator
  3. Function generator (Pasco PI 9598)
  4. 2 B-B leads
  5. Bausch & Lomb lamp
  6. Paper Screen (not shown)
  1. Place the MMD (#2) on top of the vibrator.
  2. Connect the vibrator to the function generator using the two leads.
  3. Turn on the generator and set the output to a sine wave, amplitude near middle.
  4. Vary the frequency up to 60-70 Hz and observe the behavior of the molecules.
  5. Remove the pressure plate from the top and repeat step 4.

For easy viewing, the vibrator can be shadow-projected.

Kinetic Theory (Cenco)

Demo: TH-D-KC
Pira Index: 4D 30.10

Demonstrates fundamental principles of gas mechanics. (Boyle’s Law, Van der Waal’s corrections & Avagadro’s Law)

 Lab Equipment  Directions
  1. Kinetic Theory Apparatus
  2. Plastic Pulley and 90° clamp
  3. Small Weights (two 2g, one 5g, one 1g)
  1. Align pulley so that the string attached to the metal slider hangs straight down into the middle of the cylinder, with the counterbalance mass hanging alongside the cylinder. The metal slider MUST move up and down in the piston freely.
  2. Turn on the apparatus, and adjust speed to see the small beads push up the air piston. The faster it goes, the harder they push on the piston.
  3. Additional weights may be added to the top disk of piston assembly.

Crooke’s Radiometer

Demo: TH-D-CR
Pira Index: 4D 20.10

 Lab Equipment  Directions
  1. Crooke’s Radiometer
  2. Flashlight
  3. Spray component cooler

Light hitting vanes causes them to heat up. Since black side absorbs more than white, the black side gets warmer. As moving particles inside the radiometer strike the black side of vanes, they take on more energy than those hitting the white side, and they “kick” off with more force. The action-reaction causes the black vanes to move away from more active particles.

  1. Direct the light onto black surface.
  2. The vanes will begin to turn with the white faces leading.
  3. Spray radiometer with component cooler. The vanes will slow, stop, and reverse.

When cooler is sprayed, black radiates away more of its energy than white side, making the white side the warmer side. Particles hitting the white side take on more energy and “kick” off with more force. The action-reaction causes white vanes to move away from more active particles.

Bromine Diffusion

Demo: TC-D-BD
Pira Index: 4D 50.45

 Lab Equipment  Directions
  1. Two bromine tubes
  2. Two 2-finger clamps (connect to tubes)
  3. 90° clamp
  4. Short rod
  5. White screen
  6. Dewar, half full of liquid nitrogen
  7. Lab stand
  8. C-Clamp
  9. Protective gloves
  1. Immerse the ends (approx. 2″) of the 2 tubes in liquid nitrogen for a few moments, until the bromine solidifies.
  2. Remove the tubes from the liquid nitrogen.
  3. Compare the rate of diffusion of the tube which contains a mixture of air and bromine with the rate of diffusion for tube with only bromine (marked “B” on top).

CAUTION: If a tube should break, avoid breathing the vapors or contacting the liquid. Evacuate room and call Environmental Health & Safety at x4697.