Unit 6

Question 1

enthalpy

Answer 1

heat energy involved in a process

Question 2

exothermic

Answer 2

energy/heat is lost or released from system to surroundings
change in H is negative
reactants have greater potential energy than products
involve changes that make the bonds/bring substances closer together
-making bonds/forming IMFs

Question 3

endothermic

Answer 3

energy is absorbed or gained by system from the surroundings
change in H is positive
products have a higher potential energy than reactants
involves changes that break bonds/separate substances
-breaking bonds/IMFs

Question 4

system

Answer 4

includes the molecules we want to study

Question 5

surroundings

Answer 5

everything else (not the molecules)

Question 6

dissolving solvent-solvent

Answer 6

IMFs must break
endothermic

Question 7

dissolving solute-solute

Answer 7

IMFs must break
endothermic

Question 8

dissolving solute-solvent

Answer 8

IMFs must form
exothermic

Question 9

if more energy was needed to break attractions…

Answer 9

endothermic overall

Question 10

if more energy was released to make attractions…

Answer 10

exothermic overall

Question 11

activation energy

Answer 11

energy needed for the reaction to occur
energy used to break bonds of reactants/IMFs between substances

Question 12

catalyst

Answer 12

used to increase the reaction rate by providing an alternative pathway with lower activation energies
not consumed in the reaction
does NOT change the value for change in h

Question 13

temperature

Answer 13

a measure of the average KE of the particles of the sample

Question 14

lighter particles…

Answer 14

travel at a higher speed than heavier particles in the same sample

Question 15

heat transfer

Answer 15

hot to cold

Question 16

thermal equilibrium

Answer 16

when two substances result in the same temperature after a heat transfer
—they have the same average KE

Question 17

heat

Answer 17

q
form of energy that flows between two samples of matter because of their differences in temperature

Question 18

factors that affect heat transfer

Answer 18

mass (m)
specific heat capacity (c)
change in temp (tri t, tf-ti)

Question 19

specific heat capacity

Answer 19

the energy required to raise the temp of one gram of a substance by 1 degree celsius
resistance to change
J/g*C

Question 20

calorimetry equation

Answer 20

q=mc(change)t

Question 21

first law of thermodynamics

Answer 21

energy cannot be created or destroyed

Question 22

temperature during a phase change

Answer 22

does NOT change
potential energy

Question 23

calculating q during a phase change

Answer 23

q=n*changeH
n = moles of substance
change H fusion = energy required to melt/freeze a substance (s<–>l)
change H vaporization = energy required to boil/condense a substance (l<–>g)

Question 24

heat capacity

Answer 24

he amount of heat necessary to raise an object’s temperature by one degree Celsius

Question 25

specific heat

Answer 25

Specific heat refers to the amount of heat necessary to raise the temperature of one gram of a pure substance by one degree Celsius.

Question 26

molar heat capacity

Answer 26

specific heat capacity * molar mass

Question 27

enthalpy of a reaction is aka

Answer 27

energy/heat of a reaction
change in h

Question 28

change in h (enthalpy) forward and backwards

Answer 28

equal and opposite

Question 29

use constant-pressure calorimetry when…

Answer 29

observing heat transfers between objects
reactions between solutions

Question 30

use constant-volume bomb calorimetry…

Answer 30

filed with O2 gas before placed in a bucket
sample ignited electrically
heat produced can be determined by measuring temp increase in the surrounding water
often used to determine caloric value of food

Question 31

bond enthalpy

Answer 31

the energy required to break the bond

Question 32

bond breaking is

Answer 32

endothermic, releases energy

Question 33

energy is ___ to break bonds

Answer 33

added

Question 34

energy is ____ to make bonds

Answer 34

released

Question 35

calculating delta h when given LDSs

Answer 35

sum(bond enthalpies of bonds broken (reactants))-sum(bond enthalpies of bonds formed (products))

Question 36

delta h

Answer 36

enthalpy

Question 37

bond breaking is

Answer 37

endotherimc

Question 38

bond forming is

Answer 38

exothermic

Question 39

hess’s law

Answer 39

delta h for overall reaction is sum of enthalpy changes for individual steps

Question 40

if enthalpy change is reversed

Answer 40

sign of delta h is also reversed

Question 41

if temperature is measured in the surroundings…

Answer 41

think opposite

Question 42

if the temp of the solution in a styrofoam cup goes up the solution is…

Answer 42

exothermic, reaction released energy to surrounding solutions

Question 43

going up a phase change graph the reaction is

Answer 43

endothermic

Question 44

going down a phase change graph the reaction is

Answer 44

exothermic