Category Archives: Gas Law

Lungs Demonstration Model

Demo: TH-E-LD
Pira Index: 4E 20.00

Lab Equipment  Directions
  1. special jar with handle
  1. Make the balloons expand by pinching the rubber diaphragm and pulling it downward.
  2. Push the diaphragm upward and the balloons collapse.
  3. Note that this is similar to the way that lungs work except volume is changed by muscle action at constant atmospheric pressure when volume increases and is pushed out of lungs by the contracting rib cage when the volume decreases.

Two-Liter Gas Law Demo

Demo: TH-E-GL
Pira Index: 4E 30.00

 Lab Equipment  Directions
  1. Air/Vacuum Pump
  2. 2 Liter bottle with valve stem cap
  3. Tire pressure gauge
  4. Tire inflator tool connector
  5. Orange pressure hose (#2 – 5 stored in box)
  6. Electronic Balance

The increase in mass at each added atmosphere in the mass of 2 L of air. CRC gives the accepted mass of moist air at 22°C, and 746 mmHg = 1.17 g/L

  1. Place empty bottle on balance and press “tare” to zero the balance.
  2. Attach the pump – air side – to the valve stem and run the pump until the gauge shows 3 atm or ~44 lb/in2. Weigh the bottle at this pressure and record.
  3. Using the tire pressure gauge, release the pressure to 2 atm or ~29 lb/in2, and reweigh.
  4. Repeat step 3 to 1 atm or ~15 lb/in2.

Note that for each change of atmosphere of pressure, the mass of the bottle changes by ~2.3 grams (1.17 g/L × 2L).

Boiling Water at Reduced Pressure

Demo: TH-E-BW
Pira Index: 4E 10.11

 Lab Equipment  Directions
  1. 1000 ml flask
  2. 3-finger and 90° clamp set
  3. Stopper & tubing set
  4. Meeker Burner & Striker
  5. Lab Stand
  6. 800 ml beaker
  7. Gloves
  8. Yellow & Blue food coloring
  1. Put 2 drops of yellow food coloring in the flask and fill with approx. 500 ml H2O. Without stopper, bring to a boil. Put 2 drops of blue color in about 300 ml of water in the beaker.
  2. When the water is boiling, place the stopper set in the flask and immediately remove the heat.
  3. Quickly invert the hot flask over the beaker containing cool blue water.
  4. Watch as the partial vacuum above the hot water draws blue water into the flash. As the cool water reduces vapor volume, boiling intensities.

Boyle’s Law

Demo: TH-E-BL
Pira Index: 4E 20.25

 Lab Equipment  Directions
  1. Boyle’s Law Apparatus
  2. Air/Vacuum Pump
  1. By slightly inclining the apparatus, set the ball at the 20 cm division. When the ball reaches that division, put the apparatus back in a horizontal position.
  2. Connect the vacuum hose to the nozzle of the apparatus. Turn on the pump and adjust knob (A) until the gauge reads 0.5.
  3. Record the position of the ball.
  4. Disconnect the vacuum side and connect the air side of the pump.
  5. Start the pump and adjust the valve until the gauge reads 2.
  6. Record the position of the ball.

Boyle’s Law, Hand Operated

Demo: TH-E-BH
Pira Index: 4E 20.25

 Lab Equipment  Directions
  1. Boyle’s Law apparatus (with hand-turned plunger)

To prepare this demo, turn the plunger until volume = 10. Open the valve on the left end so the trapped air starts with 1 atm of pressure. Close valve. Turn plunger outward until volume = 20. Pressure should read 0.5.

  1. Point out to the students that, at the start, Volume = 20, Pressure = 0.5
  2. Turn the plunger inward until Volume = 10, Pressure = 1
  3. Continue turning the plunger inward until Volume = 5, Pressure = 2


Absolute Zero Demonstrator

Demo: TH-E-AZ
Pira Index: 4E 30.10

 Lab Equipment  Directions
  1. Absolute zero demonstrator and thermometer.
  2. Large coffee pot with boiling [distilled] water.
  3. Large-mouth Dewar with a slurry of ice and water.
  4. Large-mouth Dewar with liquid nitrogen or dry ice pellet
  5. Meter Stick
  1. Submerge bulb in liquids of known temperature (boiling water at 100°C, ice water at 0°C, liquid nitrogen at -195.8°C, or dry ice at -78.5°C).
  2. Observe and record the corresponding gauge reading for each liquid.
  3. Plot pressure vs. temperature.
  4. Extrapolate a line to zero pressure.

Substance (Abs. Pressure; Temperature)
Liquid Nitrogen (4.5; -198.5°C)
Ice Water (14; 0°C)
Hot Water (18; 91°C)