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Wize University Chemistry Textbook > Phase Transitions and Phase Diagrams

Phase Changes

Kinetic Energy, Temperature, and Speed of Gas ParticlesPrevious Section
Heating CurvesNext Section
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Phase Transitions


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Terminology:
  • Know that melting means the same thing as fusion
  • Know that freezing means the same thing as crystallization
  • Boiling may also be called vapourization

Wize Concept
When ΔH > 0 we call this endothermic (heat energy is entering the system)
And when ΔH < 0 we call this exothermic (heat energy is exiting the system)

Practice: Phase Changes

Which of the following phase changes are exothermic?

I. Condensation
II. Vapourization
III. Freezing
IV. Deposition

Extra Practice
What physical property of water is unusual?
The normal melting point of a solid is:
Which of the following phase changes is referred to as fusion?
Phase changes
Dry ice is used in fire extinguishers. The dry ice is stored in the cylinder in a solid form. When sprayed on a fire it quickly changes into the gas known as carbon dioxide (CO2).
What is this change of state called?
Phase change
When the temperature of a liquid is increased a little, what happens to the particles?
Phase Diagrams
Choose which of the following statements are true:
The critical point on a phase diagram indicates where the liquid and gas phases become identical for a substance
The boiling point of a compound is defined as the temperature where the vapour pressure is equal to the surrounding pressure
Ice Block Question
The Inuit people have known for a long time that ice blocks can be sliced cleanly by laying a string across the ice block and then placing a weight on each side of that string. Explain how placing a weighed string on an ice block will slowly cut through the ice? (Hint: a picture will help.)
Phase Diagrams
The heating Curve for Water is shown below
What is happening along the line labelled A?
Which of the following phase changes are exothermic?
I. Condensation
II. Vapourization