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  Chemistry Comes Alive!
  Video

Summary

The highly improbable process of a shattered silicon wafer reassembling itself is shown. The 7 thumbnail images summarize the content of the video. Click an image to see the image gallery.

Narration

Narration

When a silicon wafer is shattered, the pieces are no longer connected. The process is shown in reverse. The shattered pieces of a silicon wafer "assemble themselves" back into the original wafer. The situation shown is so highly improbable that we would not expect to observe it in nature.

Discussion

Entropy is a measure of disorder, which is related to the number of arrangements that are possible for a system. A disordered system has many ways of being arranged and a high probability of existing. An ordered system has few ways of being arranged and a low probability of existing. For example, if you spill a glass of water it is highly improbable that the water will fall to the floor in the shape of the glass because many more arrangements of the water molecules are possible if the water spreads out over the floor. The water molecules are more disordered on the floor than in the glass.

A spontaneous change has a natural tendency to occur without outside intervention. The driving force for a spontaneous process is an increase in the entropy (and disorder) of the universe.

The four "processes" shown here have been constructed from videos of actual spontaneous changes by reversing the sequence of frames (running the movie backward).

"Unexploding" nitrogen triiodide: In this "process" the products of the explosion of nitrogen triiodide (and the surrounding material) reassemble into the original configuration before the explosion. The entropy change of the universe during this "process" is very negative. The nitrogen triiodide and surrounding material are more ordered when reassembled. The actual explosion transfers considerable heat to the surroundings which increases the disorder there as well. When the chemical is "unexploded," the surroundings also would grow more ordered.

"Unmelting" an ice cube: In this "process" water vapor condenses into boiling water and then freezes into a fully formed ice cube. Of course water vapor actually can change to the more ordered solid form if cooled below 0 degrees Celsius (we see this on a frosty morning) . The formation of frost is spontaneous because the heat transfered from the water causes an increase in disorder in the surroundings. The "process" we show here is not spontaneous, though,because the temperature is clearly above 0 degrees Celsius (the water was boiling when the ice cube formed) and because of the shape of the ice formed. It is highly improbable that the water molecules would arrange themselves into the shape of an ice cube when the solid is formed.

"Unmixing" a dye: In this "process" a dye that has been partially mixed in an aqueous solution reassembles into a drop of dye on the surface of the water. "Unmixing" the dye would result in an increase in the order (and decrease in the entropy) of the dye and water. The change in the disorder of the rest of the universe (the surroundings) would be small so this "process" would result in a net increase in order.

"Unshattering" a silicon wafer: In this "process" pieces of a shattered silicon wafer reassemble into the more ordered single wafer.

Discussion

Entropy is a measure of disorder, which is related to the number of arrangements that are possible for a system. A disordered system has many ways of being arranged and a high probability of existing. An ordered system has few ways of being arranged and a low probability of existing. For example, if you spill a glass of water it is highly improbable that the water will fall to the floor in the shape of the glass because many more arrangements of the water molecules are possible if the water spreads out over the floor. The water molecules are more disordered on the floor than in the glass.

A spontaneous change has a natural tendency to occur without outside intervention. The driving force for a spontaneous process is an increase in the entropy (and disorder) of the universe.

The four "processes" shown here have been constructed from videos of actual spontaneous changes by reversing the sequence of frames (running the movie backward).

"Unexploding" nitrogen triiodide: In this "process" the products of the explosion of nitrogen triiodide (and the surrounding material) reassemble into the original configuration before the explosion. The entropy change of the universe during this "process" is very negative. The nitrogen triiodide and surrounding material are more ordered when reassembled. The actual explosion transfers considerable heat to the surroundings which increases the disorder there as well. When the chemical is "unexploded," the surroundings also would grow more ordered.

"Unmelting" an ice cube: In this "process" water vapor condenses into boiling water and then freezes into a fully formed ice cube. Of course water vapor actually can change to the more ordered solid form if cooled below 0 degrees Celsius (we see this on a frosty morning) . The formation of frost is spontaneous because the heat transfered from the water causes an increase in disorder in the surroundings. The "process" we show here is not spontaneous, though,because the temperature is clearly above 0 degrees Celsius (the water was boiling when the ice cube formed) and because of the shape of the ice formed. It is highly improbable that the water molecules would arrange themselves into the shape of an ice cube when the solid is formed.

"Unmixing" a dye: In this "process" a dye that has been partially mixed in an aqueous solution reassembles into a drop of dye on the surface of the water. "Unmixing" the dye would result in an increase in the order (and decrease in the entropy) of the dye and water. The change in the disorder of the rest of the universe (the surroundings) would be small so this "process" would result in a net increase in order.

"Unshattering" a silicon wafer: In this "process" pieces of a shattered silicon wafer reassemble into the more ordered single wafer.

Keywords

Thermodynamics

These ChemEd DL Resource Groups Include This Video

Entropy
Enthlapy-Thermodynamics

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