First law of thermodynamics

temperature

average kinetic energy of the particles in a sample

why is temperature average

substances are made of constantly moving particles

can bounce off of each other erratically

kinetic energy formula

KE=1/2mv²

0K

absolute zero temp

no kinetic energy

Maxwell boltzmann distributino diagram

higher average kinetic energy → higher temperature …?

energy

ability of matter to do stuff/cause a change

joule

SI unit for energy

thermochemistry

study of energy changes esp heat that accomapny chem rxns and physical processes

2 types of energy

1. kinetic energy

2. potential energy

calorie (Cal)

common unit of energy

how man cal in a Cal

1000 cals

cal → J

1 cal=4.18J

kinetic energy

energy due to motionw

what does kinetic energy depend on

depends on speed and mass

potential energy

energy due to position and size

stored energy

first law of thermodynamics

energy can be converted from 1 form to another, but cannot be created nor destroyed

other name for first law of thermodynamics

law of conservation of energy

system

particular part of the universe on which we focus attention

surroundings

everything else besides the systme

system and surroundings equivalence equatin

qsystem = -q surroundings, or vice versa

what is q

heat

internal energy (E)

sum of all possible forms of energy in teh system

internal energy equation

E=PE+KEj

exothermic rxn

process in which eat flows from system to surroundings

endothermic process

heat flows to system from surroundings

types of systems

1. open

2. closed

3. isolated

open system

free exchange across system boundaries

closed system

energy can be exchanged but matter cannot

isolated system

no matter or energy crosses system boundaries

how is energy exchanged

heat exchange

heat

energy transferred between systems from temp diff

what is heat measured in

joules

zero law of thermodynamics

heat spontaneously flows from high temp to lower until equilibrium

room temp

25C

body temp

37

is there heat flow at equilibrium

there is no heat flow at equilibrium

chemical potential energy

energy of a substance due to temperature

potential energy diagram

shows change in potential energy in a system as reacting to products

heat of rxn (q)

heat released or absorbed during a chem rxn

ΔH

qmolrxn

enthalpy

ΔH

activation energy

energy inputed to start rxn

thermochemical equations

include value for heat absorbed or released when a rxn occurs

specific heat capacity

energy needed to raise temp of 1g of substance by 1C or 1K

units of specific heat capacity

J/gC or J/gK

what does a lower heat cap mean

easier to heat up

calorie

amount of energy needed to raise 1g of water by 1c or 1k

specific heat of h20

4.18

heat capacity

amount of heat needed to raise or lower the temp of a whole substance by 1C

state functions

independent of how the changes take place

volume, temp, ΔH, pressure, etc

bond energy/enthalpy

energy absorbed when bodns are broken

when is bond energy endothermic

breaking

when is bond energy exothermic

for forming

relationship between bond energy and stability

the higher the bond eneryg, the more stable the bond

how is bond energy tabulated

positive values

rules for calculating ΔH from bond enthalpy

1. draw lewis structures for both reactants and products

2. calculate total amount of energy absorbed to break bonds (psoitive)

3. calculate amount of energy released when bonds of products form (negative)

   1. ΔH is the difference between these.values

what kind of bond does N2 have

triple

what kindo f bond does 02 have

double

hess’s law of heat summation

if a rxn is carried out in a series of steps, ΔH for the net rxn will be equal to the sum of the enthalpy charges for the individual steps

rules for manipulating paths with hess’s law

1. if a rxn is reversed, the sign of ΔH is too

2. if coefficients in a balanced eqn are multiplied or divided by an integer, so are the ΔH values

3. Formulas cancelled from both sides of eq must be substances in identical physical states

standard state

set of criteria that allows us to study rxns under same conditions

standard heat of rxn (ΔHrxn)

1 atm, 25C

standard formation rxns

rxn that forms exactly 1 mol of a compound from its elements in standard state

standard state of an element

most stable form of an element at standard state

what is carbon anturally found as

graphite

standard enthalpy of formation

amount of energy absorbed or released qhen forming 1 mole of a compound from elements in their most stable form at standard state

baseline for comp

methods for calculating enthalpy

1. calorimetry

2. ΔHf

   1. hess’s law

why do elements form bons

to become more stable

lower energy means more stability

in nature, things go towards lower energy

energy is loewr bc released when bond is formed

total energy of universe

0…?

methods for calculating enthalpy

• calorimetry - mcΔT → kJ/mol rxn

• Δ°Hf

• Hess’s law