States of Matter: Solid, Liquids and Phase Changes

Question 1

crystalline solids

Answer 1

• well-ordered matter within the solid
• arrangement of atoms in the solid repeats itself

Question 2

amorphous solids

Answer 2

don’t have extensive ordering of particles

Question 3

types of crystalline solids

Answer 3

• molecular solids
• covalent network solids
• metallic solids
• ionic solids

Question 4

molecular solids

Answer 4

molecules held together by intermolecular forces, with relatively low melting points (eg ice or benzoic acid)

Question 5

covalent network solids

Answer 5

extended structures of atoms held together by covalent bonds with very high melting points

Question 6

allotropes

Answer 6

different structural forms of an element

Question 7

metallic solids

Answer 7

• metallic bonding between atoms
• metal atoms as cations in sea of delocalised electrons
• high electrical conductivity
• malleable, ductile

Question 8

ionic solids

Answer 8

held together by electrostatic attraction between cations and anions, with high melting points

Question 9

describe how most liquids are molecular

Answer 9

intermolecular forces keep particles close together but not strong enough to keep particles from moving past each other

Question 10

define surface tension

Answer 10

amount of energy required to expand a liquid surface

Question 11

how does surface tension work?

Answer 11

at top - intermolecular attractions from below mean that the net attraction is down, causing surface to contract.
in the middle - there are intermolecular attractions in all directions; no net attraction

Question 12

how does strength of forces between particles in a liquid affect surface tension?

Answer 12

the stronger the forces between particles in a liquid, the greater the surface tension

Question 13

define capillary action

Answer 13

the rising of a liquid in a narrow space against the pull of gravity

Question 14

cohesive molecules

Answer 14

between molecules

Question 15

adhesive forces

Answer 15

between molecules and container walls

Question 16

how does water rise in a capillary tube?

Answer 16

• strong H-bonding interactions between the water and glass (SiO2) pull the water up
• gravity and cohesive forces pull the liquid down

Question 17

diagram for water in a tube when adhesive>cohesive and vice versa

Question 18

gas -> solid

Answer 18

deposition

Question 19

solid -> gas

Answer 19

sublimation

Question 20

sold -> liquid

Answer 20

fusion (melting)

Question 21

liquid -> gas

Answer 21

vaporisation

Question 22

gas to liquid

Answer 22

condensation

Question 23

liquid to solid

Answer 23

freezing

Question 24

attractive forces in solids, liquids, gases

Answer 24

solid: many attractive forces
liquid: some attractive forces
gas: no attractive forces

Question 25

breaking attractive forces

Answer 25

requires (absorbs) energy: endothermic, so ∆H is positive
- adding heat increases temperature, increases KE, and overcomes attractive forces

Question 26

forming attractive forces

Answer 26

releases energy: exothermic ∆H is negative

Question 27

graph for phase changes

Answer 27

moving from one state of matter to another

Question 28

how does ∆H of vaporisation relate to ∆H of fusion?

Answer 28

∆H(vap)>∆H(fus) for all substances

Question 29

what type of process is a phase change?

Answer 29

a spontaneous process

Question 30

spontaneous

Answer 30

∆G (change in free energy) is negative

Question 31

equation for ∆G

Answer 31

∆G=∆H-T∆S
both ∆H and ∆S determine whether a process occurs spontaneously

Question 32

∆H =

Answer 32

change in enthalpy due to phase change

Question 33

∆S =

Answer 33

change in entropy due to phase change

Question 34

entropy, S

Answer 34

the greater the degree of randomness or disorder in a system, the greater its entropy

Question 35

∆S =

Answer 35

S (final) - S (initial)

Question 36

for a reaction to be favourable, ∆S must be

Answer 36

positive

Question 37

solid -> liquid -> gas requires

Answer 37

heat and increases entropy

Question 38

describe gas-liquid equilibrium and draw a graph for it

Answer 38

as equilibrium between Rate(vap) and Rate(cond) is achieved, gas pressure reaches a constant value

Question 39

vapour pressure

Answer 39

the pressure of gas in equilibrium (co-existing) with its liquid (or solid) at a specified temperature

Question 40

vapour pressure depends on

Answer 40

temperature and the strength of intermolecular forces

Question 41

effect of boiling point on vapour pressure

Answer 41

• the temperature at which vapour pressure of a liquid equals the external pressure
• enough kinetic energy to vaporise against external pressure; water can form vapour bubbles within

Question 42

normal boiling point

Answer 42

boiling point at 1atm

Question 43

effect of intermolecular forces on vapour pressure

Answer 43

greater intermolecular forces:
- fewer molecules escape liquid
- more KE required to overcome

Question 44

why Hvap is greater than H fus

Answer 44

In the change from solid to liquid, the kinetic energy of the molecules must
increase only enough to partially offset the intermolecular attractions between molecules. In the change from
liquid to gas, the kinetic energy of the molecules must increase enough to overcome the intermolecular forces

Question 45

does Xe have a lower or higher boiling point than Iodine

Answer 45

Xe would have a lower boiling point than iodine. Both are nonpolar with dispersion forces, but the forces
between xenon atoms would be weaker than those between iodine molecules since the iodine molecules are more
polarizable because of their larger size