Phase Changes Flashcards
The properties of a phase are determined by the balance of what?
The potential and kinetic energy of particles
What two forces determine the potential energy of a sample of matter?
Intramolecular and intermolecular forces
Among solids, liquids, and gases, which has the strongest intermolecular forces?
Solids
The temperature and kinetic energy of particles rises in an endothermic or exothermic phase change?
Endothermic
In an endothermic phase change, do intermolecular forces become stronger or weaker?
Weaker
The temperature and kinetic energy of particles decreases in an endothermic or exothermic phase change?
Exothermic
In an exothermic phase change, do intermolecular forces become stronger or weaker?
Stronger
What is vaporization?
Liquid to gas
What is sublimation?
Solid to gas
What phase change is fusion?
Melting (solid to liquid)
What is deposition?
Gas to solid
Is melting/fusion exothermic or endothermic?
Endothermic
Is deposition exothermic or endothermic?
Exothermic
Is vaporization exothermic or endothermic?
Endothermic
Is sublimation exothermic or endothermic?
Endothermic
Is freezing exothermic or endothermic?
Exothermic
Is condensation exothermic or endothermic?
Exothermic
-ΔH fus is the enthalpy change of which phase change?
Freezing (opposite of melting/fusion)
-ΔH vap is the enthalpy change of which phase change?
Condensation (opposite of vaporization)
-ΔH subl is the enthalpy change of which phase change?
Deposition (opposite of sublimation)
Does it take more energy to melt a solid or vaporize a liquid?
Vaporize a liquid because more energy is required to completely separate molecules to make a gas.
Within a phase, increasing heat does what?
Increases temperature
At melting and boiling points, what does heat added to a system do?
It goes to overcoming intermolecular forces
At melting and boiling points, does heat added to a system change the temperature?
No, the temperature remains constant until the intermolecular forces are broken
What formula represents the energy associated with heating within a phase?
q = mcΔT
What formula represents the energy associated with a phase change?
q = (ΔH phase change)(moles)
How do you calculate the total energy of a phase change?
Add the energies of each step
On a phase diagram, what is a fusion curve?
The line between solid and liquid
On a phase diagram, what is a vaporization curve?
The line between liquid and gas
On a phase diagram, what is a sublimation curve?
The line between gas and solid
What is a supercritical fluid?
A substance at a temperature and pressure above the critical point where distinct liquid and gas phases do not exist.
Why does the fusion curve for water have a negative slope?
Ice is less dense than liquid water
When a given pressure and temperature fall on the vaporization curve of a phase diagram, what two things are in equilibrium?
The liquid and gas phases
