Chem 1C, Chapter 9., Energy, Enthalpy, And Thermochemistry

Front 1

energy

Back 1

the capacity to do work or cause heat flow.

Front 2

law of conservation of energy

Back 2

energy can be converted from one form to another but can be neither created nor destroyed; the energy of the universe is constant.

Front 3

potential energy (P.E.)

Back 3

energy resulting from position or composition.

Front 4

kinetic energy

Back 4

energy resulting from the motion of an object; dependent on the mass of the object and the square of its velocity.
KE = ½mv²
...Where m = mass, v = velocity.

Front 5

frictional heating

Back 5

the transfer of energy to the surrounding.

Front 6

heat

Back 6

energy transferred between two objects caused by a temperature difference between them.

Front 7

work

Back 7

force acting over a distance.

Front 8

pathway

Back 8

the specific conditions of a path,which divides energy between work and heat depending on those conditions; the way that energy transfer is divided between work and heat. Different paths result in different divisions.

Front 9

state function (or state property)

Back 9

a property that is independent of the pathway.

Front 10

system (thermodynamics)

Back 10

that part of the universe on which attention is to be focused.

Front 11

surroundings

Back 11

everything in the universe surrounding a thermodynamic system.

Front 12

exothermic

Back 12

refers to a reaction where energy (as heat flow) out of the system.

Front 13

endothermic

Back 13

refers to a reaction where energy (as heat) flows into the system.

Front 14

thermodynamics

Back 14

the study of energy and its interconversions.

Front 15

first law of thermodynamics

Back 15

the energy of the universe is constant; same as the law of conservation of energy.
ΔE = q – w'
...where w' signifies work from the surrounding's point of view.

Front 16

internal energy (E)

Back 16

sum of the kinetic and potential energies of all of the “particles” of a system; a property of a system that can be changed by a flow of work, heat, or both; ΔE = q + w, where ΔE is the change in the internal energy of the system, q is heat, and w is work.

Front 17

enthalpy (H)

Back 17

a property of a system equal to E + PV, where E is the internal energy of the system, P is the pressure of the system, and V is the volume of the system. At constant pressure, where only PV work is allowed, the change in enthalpy equals the energy flow as heat.
H = E + PV

Front 18

calorimeter

Back 18

a device that can be used to determine the heat associated with a chemical reaction.

Front 19

calorimetry

Back 19

the science of measuring heat.

Front 20

heat capacity (C)

Back 20

the amount of energy required to raise the temperature of an object by one degree Celsius.
C = (heat absorbed) / (increase in temperature)

Front 21

molar heat capacity

Back 21

the energy required to raise the temperature of one mole of a substance by one degree Celsius.

Front 22

specific heat capacity

Back 22

the energy required to raise the temperature of one gram of a substance by one degree Celsius.

Front 23

constant pressure calorimetry

Back 23

used in determining the changes in enthalpy occurring in solution.

Front 24

bomb calorimeter

Back 24

used to study the energy changes in reactions under conditions of constant volume.

Front 25

Hess's law

Back 25

in going from a particular set of reactants to a particular set of products, the enthalpy change is the same whether the reaction takes place in one step or in a series of steps; in summary, enthalpy is a state function.

Front 26

standard enthalpy of formation

Back 26

the enthalpy change that accompanies the formation of one mole of a compound at 25ºC from its elements, with all substances in their standard states at that temperature.

Front 27

standard state

Back 27

a reference state for a specific substance defined according to a set of conventional definitions.

Front 28

What are the Definitions of Standard States:

Back 28

1. For a gas the standard state is a pressure of exactly 1 atm.
2. For a substance present in a solution, the standard state is a concentration of exactly 1 M at an applied pressure of 1 atm.
3. For a pure substance in a condensed state (liquid or solid), the standard state is the pure liquid or solid.
4. For an element the standard state is the form in which the element exists (is most stable) under conditions of 1 atm and the temperature of interest (usually 25°C).

Front 29

What are the Key Concepts for Doing Enthalpy Calculations?

Back 29

1. When a reactant is reveresed, the magnitude of ΔH remains the same, but the sign changes.
2. When the balanced equation for a reaction is multiplied by an integer, the value of ΔH for that reaction must be multiplied by the same integer.
3. The change in enthalpy for a given reaction can be calculated from the enthalpies of formation of the reactants and products:
ΔH°reaction = ΣΔH°_f (products) – ΣΔH°_f (reactants)
4. Elements in their standard states are not included in the ΔHreaction calculations. That is, ΔH for an element in its standard state is zero.

Front 30

fossil fuels

Back 30

coal, petroleum, or natural gas; consists of carbon-based molecules derived from decomposition of once-living organisms.

Front 31

petroleum

Back 31

a thick, dark liquid composed mostly of hydrocarbons.

Front 32

natural gas

Back 32

usually associated with petroleum deposits and consist mostly of methane.

Front 33

coal

Back 33

formed from the remains of plants buried and subjected to pressure and heat over long periods of time.

Front 34

greenhouse effect

Back 34

a warming effect exerted by the earth's atmosphere (particularly CO2 and H2O) due to thermal energy retained by absorption of infrared radiation.

Front 35

syngas

Back 35

synthetic gas, a mixture of carbon monoxide and hydrogen, obtained by coal gasification.

Front 36

q= -x denotes an

Back 36

exothermic process

Front 37

q = +x denotes an

Back 37

endothermic process