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126 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 12
The process by which a solid changes directly into a gas without
first becoming a liquid is called sublimation. Solid air fresheners
and dry ice are examples of solids that sublime. At very low temperatures, ice will sublime in a short amount of time. This property of
ice is used to preserve freeze-dried foods.
Practice Problems
10. Classify each of the following phase changes.
a. dry ice (solid carbon dioxide) to carbon dioxide gas
b. ice to liquid water
c. liquid bromine to bromine vapor
d. moth balls giving off a pungent odor
Phase changes that release energy Some phase changes release
energy into their surroundings. For example, when a vapor loses
energy, it may change into a liquid. Condensation is the process by
which a gas or vapor becomes a liquid. It is the reverse of vaporization. Water vapor undergoes condensation when its molecules lose
energy, their velocity decreases, and hydrogen bonds begin to form
between them. When hydrogen bonds form, energy is released.
When water is placed in a freezer, heat is removed from the
water. The water molecules lose kinetic energy, and their velocity
decreases. When enough energy has been removed, the hydrogen
bonds keep the molecules frozen in set positions. The freezing point
is the temperature at which a liquid becomes a crystalline solid.
When a substance changes from a gas or vapor directly into
a solid without first becoming a liquid, the process is called
deposition. Deposition is the reverse of sublimation. Frost is an
example of water deposition.
Practice Problems
11. Classify each of the following phase changes.
a. liquid water to ice
b. water vapor to liquid water
c. dew forming on grass
d. water vapor to ice crystals
e. beads of water forming on the outside of a glass containing a
cold drink
▲
126 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 12
The process by which a solid changes directly into a gas without
first becoming a liquid is called sublimation. Solid air fresheners
and dry ice are examples of solids that sublime. At very low temperatures, ice will sublime in a short amount of time. This property of
ice is used to preserve freeze-dried foods.
Practice Problems
10. Classify each of the following phase changes.
a. dry ice (solid carbon dioxide) to carbon dioxide gas
b. ice to liquid water
c. liquid bromine to bromine vapor
d. moth balls giving off a pungent odor
Phase changes that release energy Some phase changes release
energy into their surroundings. For example, when a vapor loses
energy, it may change into a liquid. Condensation is the process by
which a gas or vapor becomes a liquid. It is the reverse of vaporization. Water vapor undergoes condensation when its molecules lose
energy, their velocity decreases, and hydrogen bonds begin to form
between them. When hydrogen bonds form, energy is released.
When water is placed in a freezer, heat is removed from the
water. The water molecules lose kinetic energy, and their velocity
decreases. When enough energy has been removed, the hydrogen
bonds keep the molecules frozen in set positions. The freezing point
is the temperature at which a liquid becomes a crystalline solid.
When a substance changes from a gas or vapor directly into
a solid without first becoming a liquid, the process is called
deposition. Deposition is the reverse of sublimation. Frost is an
example of water deposition.
Practice Problems
11. Classify each of the following phase changes.
a. liquid water to ice
b. water vapor to liquid water
c. dew forming on grass
d. water vapor to ice crystals
e. beads of water forming on the outside of a glass containing a
cold drink
▲