Category Archives: Change of State

Super Cooled H2O

[youtube id=”xP0iwiTOt8U&feature=c4-overview&list=UUJm707yMJlGpl9oCMpKtLGQ” width=”405″ height=”228″]

Demo:
Pira Index:

While ice at standard pressure will melt zero degree C, water can sometime be cooled below this temperature and remain a liquid. This is an example of supercooling. Liquid water in this state is unstable. Ice formation can be nucleation site. As the ice forms, the temperaturre will increase due to the latent heat of the ice water transition of 80 calories/gram.

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Video by Christine Hanson
Demo Description by Dr Steven W. McCauley

Hand Boiler with Light

Demo: TH-C-HB2
Pira Index:

Lab Equipment  Directions
  1. hand boiler
  2. light source
  3. small lab stand
  4. 3 finger clamp
  5. 90 degree clamp
  1. Optional – a second light source can be directed at the top of the hand boiler to force the fluid back down more quickly. Ice can be used on the top of the hand boiler to pull the fluid upwards.

Solid Nitrogen

Demo: TC-C-SN
Pira Index: 4C 20.40

 Lab Equipment  Directions
  1. Dewar of liquid nitrogen
  2. Vacuum base bell jar
  3. Large vacuum pump with hose
  4. Clear Solo cup
  5. Paper cup
  6. Nalgene Container (4″ high)
  7. Watch glass
  8. Tongs
  9. Gloves
  1. Cool down the Solo cup in the liquid nitrogen.
  2. Dip Solo cup into dewar and fill cup 2/3 full.
  3. Place the Solo cup on the platform.
  4. Put the Nalgene container over the Solo cup and turn on the vacuum pump.
  5. Watch the liquid boil and freeze.
  6. Once frozen, slowly release pressure and watch the liquid nitrogen melt.

Pulse Glass

Demo: TH-C-PG
Pira Index: 4C 33.50

 Lab Equipment  Directions
  1. Pulse Glass Apparatus
  1. Hold one of the bulbs in your hand at an angle as shown.
  2. When the expansion and condensation have reached dynamic equilibrium, the bubbles produced by expansion should match the rhythm of your pulse.

Latent Heat

Demo: TH-C-LH
Pira Index: 4C 20.59

 Lab Equipment  Directions
  1.  heat pack 
Once demo is set up – do NOT squeeze the button. Once it is activated it requires time to reset. 
  1.  Place the heat pack on the overhead. Push the button and observe the change of state.
  2. Pass the heat pack around so that students can feel the heat emitted. 
Heat pack is reusable – do NOT throw away 

Hand Boiler

Demo: TH-C-HB
Pira Index: 4C 33.50

 Lab Equipment  Directions
  1.  hand boiler apparatus with colored methyl alcohol fluid
  1.  Cup hand around the bottom chamber.
  2. Note that heat from your hand evaporates the liquid, raising pressure in the bottom chamber, forcing the liquid into the upper chamber. 
  3. Now cup hand around the upper chamber.
  4. The same effect applies to send the liquid into the opposite chamber. 

Drinking Duck

Demo: TH-C-DD
Pira Index: 4C 31.30

 Lab Equipment  Directions
  1.  drinking duck
  2. block of wood
  3. 9 oz solo cup (keep with set) 
  1.  Fill the cup with cold water and place on the block.
  2. Completely immerse the duck’s head in water for a moment.
  3. Place the duck in front of the cup. It will continue drinking by itself. 

Cryophorus

Demo: TH-C-CP
Pira Index: 4C 31.10

 Lab Equipment  Directions
  1. cryophorus apparatus
  2. dewar of liquid nitrogen
  1. Make sure all the water is in the bulb near the bent end of the tube as shown.
  2. Immerse the other bulb in the liquid nitrogen and watch for ice crystal formation. 

Boiling Water at 22 Degrees Celsius

Demo: TH-C-BW
Pira Index: 4C 30.15

 Lab Equipment  Directions
  1.  vacuum pump
  2. insulated container (dewar)
  3. coiled copper tubing
  4. flask with water (about 20 ml)
  5. lab pole
  6. 2 – two finger clamps
  7. telescope clamp
  8. dry ice (one container)
  1.  Set up the apparatus as shown below.
  2. Turn on the vacuum pump and watch for signs of boiling in the flask. Touching the flask will confirm that the temperature has not risen.