C2: Phases and Thermochemistry

Question 1

describe the phase change from:
solid to gas

Answer 1

sublimination

Question 2

describe the phase change from:
solid to liquid

Answer 2

fusion/ melting

Question 3

describe the phase change from:
liquid to gas

Answer 3

vaporization/ boiling/ evaporation

Question 4

describe the phase change from:
gas to liquid

Answer 4

condensation

Question 5

describe the phase change from:
liquid to solid

Answer 5

solidification/ freezing/ crystallization

Question 6

describe the phase change from:
gas to solid

Answer 6

deposition

Question 7

from solid > liquid > gas…
- heat is (absorbed/ released) ____
- temperature ____
- kinetic energy ____
- entropy ____
- intermolecular forces ____

Answer 7

• absorbed
• increases
• increases
• increases
• decrease

Question 8

from gas > liquid > solid …
- heat is (released/ absorbed) ____
- temperature ____
- kinetic energy ____
- entropy ____
- intermolecular forces ____

Answer 8

• released
• decreases
• decreases
• decreases
• increase

Question 9

in a phase transition diagram,
what is the heat of transition?
- heat of fusion?
-heat of vaporization?

Answer 9

the amount of energy required to to complete a transition
- the amount of heat that must be absorbed to change a solid into a liquid
- the energy absorbed when a liquid changes to a gas

Question 10

what formula is used when trying to find the amount of heat within a phase transition diagram?
- if change in H and q are positive, heat is ____
- if change in H and q are negative, heat is ____

Answer 10

q= n x change in H(phase change)
where q= heat
n= # of moles of substance
- absorbed
- released

Question 11

what is the formula for heat capacity?

Answer 11

q= mc x change in T
where q= heat
m= mass of the sample
c= specific heat of the substance

Question 12

what is a calorie?

Answer 12

the amount of heat required to raise the temperature of 1 gram of water by 1 degree C

Question 13

the specific heat of a substance depends upon its ____

Answer 13

phase (s, l, g)

Question 14

what is the SI unit for energy?

Answer 14

joule

Question 15

1 cal = ____ J

Answer 15

4.2

Question 16

which 11 elements are gases at standard state conditions?

Answer 16

H2, N2, O2, F2, Cl2, He, Ne, Ar, Kr, Xe, Rn

Question 17

which 2 elements are liquid at standard state conditions?

Answer 17

Hg and Br2

Question 18

what are the 7 diatomic elements at standard state conditions?
- what is a good mnemonic to remember these?

Answer 18

H2, N2, O2, F2, Cl2, Br2, I2
- BrINCl HOF

Question 19

for molecular solids..
- describe their structure
- are they malleable or rigid?
- are they conductors?
- are their BPs and MPs low or high?

Answer 19

• nonmetal atoms connected by covalent bonds, molecules have weak intermolecular forces
• soft
• no
• low

Question 20

for ionic solids..
- describe their structure
- are they malleable or rigid?
- are they conductors?
- are their BPs and MPs low or high?

Answer 20

• metal cations and nonmetal anions from a crystal lattice locked in by electrostatic interaction
• rigid
• no
• high

Question 21

for metallic solids..
- describe their structure
- are they malleable or rigid?
- are they conductors?
- are their BPs and MPs low or high?

Answer 21

• metal atoms form cations with delocalized valence electrons
• malleable
• yes
• medium

Question 22

for covalent networks ..
- describe their structure
- are they malleable or rigid?
- are they conductors?
- are their BPs and MPs low or high?

Answer 22

• carbon or metalloid atoms form an extended network of covalent bonds
• rigid
• mostly no
• very high

Question 23

in a phase transition diagram..
- which is on the x and y axis?
- inclines indicate ___ changes and plateaus indicate ____ changes. can both of these happen at the same time?
- the first incline indicates a ____ state, second a ____ state, and third a ____ state
- the first plateau indicates ____ and the second indicates ____

Answer 23

• x axis= heat (q), y axis= temperature
• temperature; phase. cannot happen simultaneously
• solid; liquid; gas
• fusion; vaporization

Question 24

what is specific heat (c)?
- what does a large c mean?
- small c?

Answer 24

the amount of heat required to increase the temperature of 1 gram (or 1 mol) of a substance by by 1 degree C or 1K
- slower to heat or cool
- faster to heat or cool

Question 25

what is heat capacity (C)

Answer 25

the amount of heat required to increase any amount of a substance by 1 degree C or 1K

Question 26

in phase change diagrams…
- what goes on the x and y axis?
- what does it look like?
- what is the triple point?
- what is the critical point?
- what is supercritical fluid?

Answer 26

• x axis= temperature, y axis= pressure
• solid towards top left, then liquid in middle, then gas on bottom center
• where the 3 phases coexist
• when the phase ends
• when you go past the critical point where the phases do not exist

Question 27

what does the phase diagram for water look like?

Answer 27

slightly negative slope

Question 28

what happens to waters melting point when external pressure decreases?

Answer 28

it increases

Question 29

the temperature of a substance is a measure of its internal ____ and is not changing

Answer 29

kinetic energy

Question 30

why does a pot of boiling waters temperature remain constant despite the addition of heat?

Answer 30

the heat is used to break hydrogen bonds rather than increase the temperature