Sublimation and Deposition

SKILL LEVEL

Middle school, High School

TRY IT!

Sublimation occurs when a substance passes from the solid phase directly to the gas phase without first becoming a liquid.  If you've ever seen dry ice, the solid form of carbon dioxide that is so fun to drop into warm water to make fog, you have already observed sublimation!

The opposite of sublimation is deposition, which is the process by which a solid is formed directly from a gas.

A piece of dry ice on your countertop won't form a puddle of liquid carbon dioxide before becoming a gas.  Instead, the carbon dioxide will sublimate directly from the solid phase to the gas phase.

In this experiment, you will sublimate the active chemical, called 1,4-dichlorobenzene, in bathroom deodorizer.  Unlike dry ice, you will have the opportunity to also observe the deposition of 1,4-dichlorobenzene.  If all goes well, you should observe some beautiful needle-like crystals in the end.

SUPPLIES, TOOLS, MATERIALS

  • Two 8 oz plastic disposable cups
  • Masking tape
  • Shallow Tray
  • Water
  • Ice
  • BowlFresh bathroom deodorizer
  • Gallon plastic bags
  • Hammer
  • Latex, nitrile, or vinyl gloves
  • Safety goggles
Deodorizer

INSTRUCTIONS

Does 1,4-dichlorobenze sound like a chemical you would want to handle with your hands or get in your skin or eyes? Of course not!  You'll want to wear gloves and eye protection throughout this experiment.

  1. Place the deodorizer, package and all, inside of a sealed plastic gallon size bag.
  2. Tap on the deodorizer with your hammer until it becomes a fine powder.  The packaging will rip open inside the gallon bag as soon as you begin hitting it with the hammer.
  3. Carefully open the baggie and place a heaping spoonful into a plastic cup.  Now reseal the bag and dispose of the remaining chemical.
  4. Place another cup upside down on top of the cup that contains the deodorizer.  Seal the two cups together with masking tape until the system is air-tight.
  5. Prepare some warm water in your microwave.  It does NOT need to be boiling, just slightly more warm than what you can get from the tap.  Fill your shallow container with the warm water to a depth of about 3 cm.
  6. Place your two taped cups in the warm water.
  7. Set a few ice cubes on top of the two cups and wait about ten minutes, being careful not to allow the cups to topple.
  8. Look at bottom side of the top cup (do not break the seal!).  You should see hundreds of tiny stalactite-like crystals that have deposited there directly from the gas phase.
  9. Also look at the bottom of cup and note any changes in the appearance of the powder you placed there.
  10. Dispose of the sealed container, remove and dispose of your gloves, and wash your hands with plenty of soap!
Sublimation

QUESTIONS TO CONSIDER

  1. Look up and define the following terms:
    Melting
    Freezing
    Vaporization
    Condensation
    Sublimation
    Deposition
  2. Indicate whether each of the above processes is endothermic (absorbs heat energy, feels cool to touch) or exothermic (releases heat energy, feels warm to touch).
  3. Record your observations from the sublimation and deposition of 1,4-Dichlorobenzene.  Describe the crystals in detail.