Ch 5 Terms

Question 1

Hess Law

Answer 1

Indirect determination of OH; if you add several reactions together to get an overall reaction, you can also add their 🔺 H together

Question 2

Energy

Answer 2

Transfer of heat

Question 3

Thermochemistry

Answer 3

Study of heat absorbed or released in reactions

Question 4

Chemical potential energy

Answer 4

Energy stored in chemical bonds
*Energy is required to to break ANY BOND

Question 5

Heat (q)

Answer 5

Energy needed to increase an objects temperature

Question 6

System

Answer 6

What we’re studying
Always the REACTION

Question 7

Surroundings

Answer 7

Everything else
Ex: water, beaker, thermometer, you

If heat is lost by system, the surroundings gain it and vice versa

Question 8

Exothermic

Answer 8

Heart is being released by system
The surroundings gain heat
You feel warmth
All combustions
q system= -

Question 9

When discussing heat, we take the ___ perspective

Answer 9

Systems

Question 10

Endothermic

Answer 10

Heat is absorbed by the system
Surroundings lost heat
You feel cold
q system = +

Question 11

Joule to calorie conversion

Answer 11

1 calorie = 4.18 J

Question 12

Heat capacity

Answer 12

Amount of heat needed to raise the temp of a substance by 1 degree Celsius

Depends on:
1. Substance density
2. Mass

Question 13

Specific heat (c)

Answer 13

Amount of heat needed to raise one gram of substance by 1 degree Celsius

Question 14

Enthalpy

Answer 14

Another term for heat (at constant pressure)

Heat = Enthalpy

Question 15

Enthalpy changes depend on ____

Answer 15

Reaction conditions

Question 16

Scientists pick a standard state

Answer 16

25 c and 1 atm (pressure at sea level)

Question 17

Standard heat of formation

Answer 17

Heat absorbed or released when 1 mol of a substance is formed from its elements in their standard state

Question 18

Calorimetry

Answer 18

A lab technique to determine q for 🔺H for a reaction

Question 19

Calorimeter

Answer 19

An insulate device used to hold a reaction

Ex: styrofoam cup

“Coffee cup calorimetry”

Question 20

Enthalpy is an extensive property

Answer 20

Heat depends on stoich
Big Bonfire = more heat

Question 21

The enthalpy change for a reaction is equal in magnitude, but opposite in sign to H for the reverse reaction

Question 22

The enthalpy change for a reaction depends on the state of the

Answer 22

Reactants and products

Question 23

Thermochemical equation

Answer 23

Reaction with an H value

Question 24

Constant pressure calorimetry

Answer 24

all reactions we study will occur in a coffee cup open to air (atmosphere pressure)

Question 25

Solid to Gas

Answer 25

Sublimation (dry ice) (endo)

Question 26

During a phase change

Answer 26

Temp does not change

Question 27

Gas to Solid

Answer 27

Deposition (exo)

Question 28

Liquid to solid

Answer 28

Freezing or solidification (exo)

Question 29

Gas to liquid

Answer 29

Condensation (exo)

Question 30

Solid to liquid

Answer 30

Melting/fusion (endo)

Question 31

Liquid to gas

Answer 31

Vaporization/evaporation (endo)

Question 32

Molar heat of fusion

Answer 32

Energy needed to melt 1 mol of substance (6.01 kj/mol)

Question 33

Molar heat of solidification

Answer 33

Energy released when 1 mol of a substance freezes (-6.01 kj/mol)

Question 34

Molar heat of vaporization

Answer 34

Energy needed to vaporize 1 mol of a substance (40.7 kj/mol)

Question 35

Molar heat of condensation

Answer 35

Energy released when 1 mol condenses (-40.7 kj/mol)

Question 36

Molar heat of condensation

Answer 36

Energy released when 1 mol condenses (-40.7 kj/mol)

Question 37

Going up every q must be positive

Answer 37

Going down every q must be negative

Question 38

Going up every q must be positive

Answer 38

Going down every q must be negative