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AP Chemistry > Chapter 5: energy, heat, and work > Flashcards

Chapter 5: energy, heat, and work Flashcards

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1
Q

a complete chemical equation includes a quantitative measure of the

A

energy produced or consumed

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2
Q

thermochemistry is the study of the

A

relationship between heat and chemical reactions

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3
Q

all forms of energy fall into two categories:

A

kinetic energy and potential energy

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4
Q

kinetic energy is energy possessed by matter because it is

A

in motion

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5
Q

the kinetich energy of an object depends on both its

A

mass (m) and its velocity (v)

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6
Q

kinetic energy =

A

1/2m * v^2

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7
Q

The SI unit for energy is the

A

joule (J)

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8
Q

joule=

A

[(kilogram)(meter)^2] / (second)^2

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9
Q

thermal energy is kinetic energy in the form of

A

random motion of the particles in a sample of matter

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10
Q

the greater the temperature of the matter, the … its particles move and the …

A

faster; higher its thermal energy

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11
Q

heat is the flow of energy from … that causes a change in the …

A

one object to the other; temperature of the object

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12
Q

when heat is added to or removed from a sample, it causes a change in the

A

temperature of that sample

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13
Q

work is the application of a

A

force across some distance

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14
Q

it takes energy to perform .., so like heat, quantities of .. are expressed in units of …

A

work; work; joules

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15
Q

work can take many forms: … work, … work, … work, … work, and … work

A

mechanical; chemical; gravitational; pressure-volume; electrical

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16
Q

potential energy is energy possessed by matter because of its

A

position or condition

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17
Q

…. energy: compounds also possess … as a result of the …

A

chemical; potential energy; forces that hold the atoms together

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18
Q

in a chemical reaction, because the chemical energy of the reactants is not the same as that of the products, enrgy is either … or … during the reaction, usually in the form of …

A

absorbed; released; heat

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19
Q

system:

A

sample of matter

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20
Q

the system is the matter of

A

interest

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21
Q

the surroundings are

A

all other matter

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22
Q

surroundings include the

A

reaction container

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23
Q

law of conservation of energy states that the total energy of the … is … during a …

A

universe; constant; chemical/physical change

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24
Q

universe:

A

system + surroundings

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25
Q

energy is often … the system and the surrooundings

A

transferred between

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26
Q

law of conservation of energy is also referred to as the

A

first law of thermodynamics

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27
Q

if energy transfers between the system and the surroundings, then the total amount of energy contained in the system has

A

changed

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28
Q

energy change =

A

work + heat

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29
Q

exothermic: … to the surroundings

A

releases heat

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30
Q

endothermic: a reaction that

A

absorbs heat

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31
Q

energy can be considered a

A

reactant/product

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32
Q

SI unit of heat energy is

A

joule

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33
Q

a calorie was originally defined as the amount of heat needed to increase the …. by …, from .. to …

A

temperature of 1 g water; 1 degree celsius; 14.5 degrees C to 15.5 degrees C

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34
Q

1 cal =

A

4.184 J

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35
Q

thus, it takes … J to increase the temperature of 1 g water from 14.5 degrees celsius to 15.5 degrees celsius

A

4.184 J

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36
Q

enthalpy, H, of a system is the measure of the

A

total energy of the system at a given pressure and temperature

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37
Q

enthalpy cannot be measured, but the … that accompanies a change in the system can be measured

A

change in enthalpy

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38
Q

under conditions of constant pressure and temperature, the quanitity of heat … at constant temperature and pressure is called the

A

absorbed/given off by the system; change in enthalpy

39
Q

delta H means

A

Hfinal - Hinitial

40
Q

if the chemical reaction is exothermic, the system has …, which means that its enthalpy … and delta H is ..

A

lost energy; decreases; negative

41
Q

if the chemical reaction is endothermic, the enrgy of the system … and the sign of delta H is …

A

increases; positive

42
Q

a thermochemical equation is a chemical equation for which

A

the value of delta H is given

43
Q

the chemical reaction is assumed to occur at .., because delta H is used in the thermochemical equation

A

constant pressure and temperature

44
Q

the enthalpy is determined by

A

experiment

45
Q

in a thermochemical equation, delta H assumes that the coefficients refer to

A

molar quantities

46
Q

it is important to include the … of every substance in any …

A

physical state; thermochemical equation

47
Q

enthalpy changes are part of the … of a thermochemical equation

A

Stoichiometry

48
Q

the thermochemical equation expresses the stoichiometric relationship between the … of any substance in the equation and the …

A

number of moles; quantity of heat produced or absorbed in the reaction

49
Q

calorimetry: measurement of the heat … when the … occurs

A

released or absorbed; chemical change

50
Q

calorimeter: the device in which the … and the …

A

reaction takes place; heat is meausred

51
Q

the quantity of heat released or absorbed by the reaction causes a change in the …. which is measured with a …

A

temperature of the solution; thermometer

52
Q

for the heat to correspond to the enthalpy change of the system, the calorimeter must be operated at

A

constant pressure

53
Q

the reaction in the calorimeter proceeds at constant pressure because .. changes little during the course of the experiment

A

atmospheric pressure

54
Q

the insulation provided by the calorimeter prevents any

A

transfer of heat into or out of the calorimeter

55
Q

in a calorimetry experiment, the amount of solution must be known because the observed temperature change depends on the

A

amount of solution present

56
Q

the heat capacity of a sample is the quantity of heat required to

A

increase the temperature of that object by 1 K

57
Q

heat capacity has units of … or …, and is nearly constant for a given substance over…

A

J/K; J/ degrees C; small ranges of temperature

58
Q

the specific heat is the heat needed to …

A

increase the temperature of a 1-g sample of the material by 1 K

59
Q

1 =

A

mCsdeltaT

60
Q

q is

A

heat in joules

61
Q

m is

A

mass in grams

62
Q

Cs is

A

specific heat of sample

63
Q

(assumptions in calorimetry calculations) the heat required to change the temperature of the vessel, stirrer, and thermometer is

A

sufficiently small to be ignored

64
Q

(assumptions in calorimetry calculations) the specific heat of the solution, as long as it is dilute, is the

A

same as that of water, 4.184 J/gK

65
Q

a state function is any … that is determeined by the ..

A

property of a system; present conditions of the system

66
Q

the state function is independent of how the

A

system got to that set of conditions

67
Q

the enthalpy, and the change in enthalpy, of a chemical system is a

A

state function

68
Q

the value of delta H for a process does not depend on how the

A

process occurred

69
Q

the delta H is only dependent of the … of the system and the … of the system

A

initial state; final state

70
Q

in thermochemical equations, the coefficients refer to molar amounts, so

A

fractional coefficents can be used

71
Q

energy-level diagrams are … graphs

A

one-dimensional

72
Q

an energy-level diagram is a representation of the relative … of the …

A

enthalpies; reactnats and products of a reaction

73
Q

reversing the direction of a chemical reaction … on the reaction’s deltaH

A

changes the sign

74
Q

Hess’s law: calculating the enthalpy change in an overall chemical reaction by

A

summing the enthalpy changes of each step

75
Q

the properties that govern the combination of thermochemical equations are natural consequences of … and the fact that …

A

the law of conservation of energy; enthalpy is a state function

76
Q

the change in enthalpy for an equation obtained by adding two or more thermochemical equations is the sum of the

A

enthalpy changes of the added equations

77
Q

the enthalpy change is an … that depends on the amounts of the substances that react

A

extensive

78
Q

hess’s law lets us calculate the enthalpy change for one reaction from

A

thermochemical equations for others

79
Q

enthalpy change for any reaction is influenced by the

A

pressure and the temperature

80
Q

standard state of a substance is the … at … and the …

A

pure form; one atmosphere pressure; designated temperature (usually 298.15 K or 25.0 degrees C)

81
Q

standard enthalpy change is an enthalpy change in which all

A

reactants and products are in their standard states

82
Q

the symbol for standard enthalpy change is

A

ΔH°

83
Q

° means that all reactants and products are in the standard state of

A

1 atm pressure and 298.15 K

84
Q

a formation reaction is a chemical reaction that makes

A

one mole of a substane from its constituent elements in their standard states

85
Q

the enthalpy change for a formation reaction is symbolized by

A

ΔHf°

86
Q

the subscript f stands for

A

formation

87
Q

ΔHf° is called

A

standard enthalpy of formation

88
Q

the ΔHf° of all elements in their standard states is

A

zero

89
Q

ΔH°rxn =

A

∑mΔHf° [products] - ΣnΔHf° [reactants]

90
Q

m is the number of moles of each

A

product

91
Q

n is the number of moles of each

A

reactant

92
Q

the reactants contribute the … of their enthalpies of formation, whears products contribute the … of their enthalpies of formation

A

negative; positive

93
Q

enthalpy of combustion: the energy change for a …

A

combustion reaction

AP Chemistry (24 decks)

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