Phase Changes

Question 1

The properties of a phase are determined by the balance of what?

Answer 1

The potential and kinetic energy of particles

Question 2

What two forces determine the potential energy of a sample of matter?

Answer 2

Intramolecular and intermolecular forces

Question 3

Among solids, liquids, and gases, which has the strongest intermolecular forces?

Answer 3

Solids

Question 4

The temperature and kinetic energy of particles rises in an endothermic or exothermic phase change?

Answer 4

Endothermic

Question 5

In an endothermic phase change, do intermolecular forces become stronger or weaker?

Answer 5

Weaker

Question 6

The temperature and kinetic energy of particles decreases in an endothermic or exothermic phase change?

Answer 6

Exothermic

Question 7

In an exothermic phase change, do intermolecular forces become stronger or weaker?

Answer 7

Stronger

Question 8

What is vaporization?

Answer 8

Liquid to gas

Question 9

What is sublimation?

Answer 9

Solid to gas

Question 10

What phase change is fusion?

Answer 10

Melting (solid to liquid)

Question 11

What is deposition?

Answer 11

Gas to solid

Question 12

Is melting/fusion exothermic or endothermic?

Answer 12

Endothermic

Question 13

Is deposition exothermic or endothermic?

Answer 13

Exothermic

Question 14

Is vaporization exothermic or endothermic?

Answer 14

Endothermic

Question 15

Is sublimation exothermic or endothermic?

Answer 15

Endothermic

Question 16

Is freezing exothermic or endothermic?

Answer 16

Exothermic

Question 17

Is condensation exothermic or endothermic?

Answer 17

Exothermic

Question 18

-ΔH fus is the enthalpy change of which phase change?

Answer 18

Freezing (opposite of melting/fusion)

Question 19

-ΔH vap is the enthalpy change of which phase change?

Answer 19

Condensation (opposite of vaporization)

Question 20

-ΔH subl is the enthalpy change of which phase change?

Answer 20

Deposition (opposite of sublimation)

Question 21

Does it take more energy to melt a solid or vaporize a liquid?

Answer 21

Vaporize a liquid because more energy is required to completely separate molecules to make a gas.

Question 22

Within a phase, increasing heat does what?

Answer 22

Increases temperature

Question 23

At melting and boiling points, what does heat added to a system do?

Answer 23

It goes to overcoming intermolecular forces

Question 24

At melting and boiling points, does heat added to a system change the temperature?

Answer 24

No, the temperature remains constant until the intermolecular forces are broken

Question 25

What formula represents the energy associated with heating within a phase?

Answer 25

q = mcΔT

Question 26

What formula represents the energy associated with a phase change?

Answer 26

q = (ΔH phase change)(moles)

Question 27

How do you calculate the total energy of a phase change?

Answer 27

Add the energies of each step

Question 28

On a phase diagram, what is a fusion curve?

Answer 28

The line between solid and liquid

Question 29

On a phase diagram, what is a vaporization curve?

Answer 29

The line between liquid and gas

Question 30

On a phase diagram, what is a sublimation curve?

Answer 30

The line between gas and solid

Question 31

What is a supercritical fluid?

Answer 31

A substance at a temperature and pressure above the critical point where distinct liquid and gas phases do not exist.

Question 32

Why does the fusion curve for water have a negative slope?

Answer 32

Ice is less dense than liquid water

Question 33

When a given pressure and temperature fall on the vaporization curve of a phase diagram, what two things are in equilibrium?

Answer 33

The liquid and gas phases