Chapter 8 & 10

Question 1

Evaporation

Answer 1

• liquid –> gas

- heat/ energy is required to overcome strong forces in liquid (therefore endothermic)

Question 2

heat of vaporization/ enthalpy of vaporization

Answer 2

energy required to vaporize 1 mole of liquid at 1 atm of pressure

Question 3

heat vaporization for water

Answer 3

2260 joules per gram

Question 4

condensation

Answer 4

gas –> liquid

Question 5

equilibrium vapour pressure

Answer 5

pressure of vapour present at equilibrium

Question 6

sublimes

Answer 6

solid –> gas

Question 7

heat curve

Answer 7

plot of temperature versus time for a process where energy is added at a constant rate

Question 8

heating curve for water

Answer 8

• energy is added
• vibrations of water molecules increase as temperature rises
• molecules break loose from position
• goes from solid to liquid (plateau at 0 degrees) (all energy is used to disrupt the ice structure by breaking hydrogen bonds) (melting point)
• becomes completely liquid
• boiling point (100 degrees)
• energy added to vaporize liquid, temperature remains constant (100 degrees)
• liquid completely vapour
• temperature rises again

Question 9

melting point

Answer 9

the temperature where a solid and liquid have the same vapour pressure where the total pressure is 1 atm

Question 10

boiling point

Answer 10

• temperature at which the vapour pressure of liquid is exactly 1 atm
• 100 degrees

Question 11

phase diagram

Answer 11

represents the phases of a substance as a function of temperature and pressure

Question 12

triple point

Answer 12

• all three states of water are present

- solid and liquid water have identical vapour pressures

Question 13

critical temperature

Answer 13

the temperature above which vapour cannot be liquidated no matter what pressure is applied

Question 14

critical pressure

Answer 14

the pressure required to product liquefaction at the critical temperature

Question 15

critical point

Answer 15

• critical temperature + critical pressure
• water = 374 degree at 218 atm
• for water it is liquid/vapour line

Question 16

phase diagram for water

Answer 16

• melting point of ice decreases at external pressure increases (this happened because density of ice is less than that of liquid water at melting point)
• the solid/liquid boundary has a negative slope
• if pressure is increased and temperature is constant the ice will melt (increased pressure causes matter to reduce its volume) (ice has a larger volume than the same mass of liquid water)

Question 17

phase diagram for water in ice skating

Answer 17

pressure from skate causes it to melt

Question 18

phase diagram for water in lakes and rivers and stuff…

Answer 18

lower density of ice means that ice formed on rivers will float, giving a layer of insulation below

Question 19

phase diagram for water in boiling water

Answer 19

• liquid boils where vapour pressure equals external pressure (depends on external pressure)
• at different elevations, water boils at different temperatures

Question 20

phase diagram for carbon dioxide

Answer 20

• solid/liquid line is positive (solid carbon dioxide is more dense than liquid carbon dioxide)
• triple point: 5.1 atm, -56.6 degrees
• critical point: 72.8 atm and 31 degrees
• sublimes: -78 degrees

Question 21

calorimeter

Answer 21

device used to determine the heat associated with a chemical reaction

Question 22

calorimetry

Answer 22

• science of measuring heat
• based on observing the temperature change when a body absorbs or discharges energy as heat
• the amount of energy required depends on amount of substance present

Question 23

molar heat capacity

Answer 23

• heat capacity per mole

- J/Celsius or J/K * mol

Question 24

endothermic reaction

Answer 24

-absorbs heat from surroundings
-vaporization and fusion are some examples
decreased for surroundings (T is negative)(negative quantity)
-system has positive quantity
-enthalpy change is always POSITIVE

Question 25

exothermic reaction

Answer 25

• releases heat to surroundings
• heat released results in a temperature increase for surrounds (T is positive)(positive quantity)
• heat released by system must have reverse sign (negative quanitity)
• enthanpy change is always NEGATIVE

Question 26

heat of fusion

Answer 26

amount of heat that must be abosrbed to melt a speciic quantity of solid

Question 27

heat content/ enthalpy

Answer 27

• stored energy

- the amount of heat transferred in a process depends on the difference in the energy stored in each substance

Question 28

enthalpy change

Answer 28

the heat change that occurs at constant pressure

Question 29

qp

Answer 29

• amount of heat transferred

- it depends on mass (m), heat (s), and temperature change (T)

Question 30

specific heat of a substance

Answer 30

• it reflects its ability to absorb heat energy

- defined as the amount of heat needed to raise the temperature of one gram by one degree

Question 31

specific heat of water

Answer 31

4.18 J/gC

Question 32

temperature change (T)

Answer 32

equal to difference between final temperature and initial temperature

Question 33

s

Answer 33

specific heat

Question 34

normal boiling point

Answer 34

temperature at which the vapour pressure of the liquid is exactly 1 atm

Question 35

melting

Answer 35

solid to liquid

Question 36

evaporation

Answer 36

liquid to gas

Question 37

freezing

Answer 37

liquid to solid

Question 38

condensation (dew)

Answer 38

gas to liquid

Question 39

sublimation

Answer 39

solid to gas

Question 40

deposition

Answer 40

gas to solid

Question 41

desntiy of liquid in dry ice

Answer 41

• there is a positive slope

- therefore the solid is denser than the liquid