Chem: Thermochemistry

Define Thermochemistry

the study of energy changes that occur during a chemical reaction and changes in the state

Define energy

the ability to work or produce heat

Define temperature

a measure of the amount of kinetic energy an object/substance has

measured in C or K

Define Heat

thermal energy- energy that transfers from one object to another

measured in joules (q)

transfers because of difference in temperature

always flows from a warmer temperature to a cooler object

Which would have more thermal energy?

The one with more of a substance because it has more to transfer to

Potential Energy

stored energy that could be used

- gravitational: ball on top of a hill

- elastic: stretching a rubber band

Kinetic energy

the motion of an object

KE= 1/2 mv^2

Law of conservation of energy

energy can neither be created or destroyed

chemical potential energy

energy thats stored in the chemical bonds of a substance

determined by types of atoms and their arrangement

System

the reaction or focus

surroundings

everything around the reaction

ie. container, room, etc.

universe

system and surroundings

define exothermic process

heat is released into the surroundings by the system

exo = exit

-q

define endothermic process

heat is absorbed from the surroundings by the system

endo = in

+q

what are the 2 common units for energy?

joules

calories

how many joules are in 1 calorie?

4.184 J = 1 calorie

How many calories in 4.184 J?

1 calorie = 4.184 J

How many calories are in 1 kilo calorie?

1000 calories = 1 kilo calorie

How many calories are in 1000 calories?

1 kilo calorie = 1000 calories

define heat capacity

amount of heat needed to increase the temperature of an object by 1'C

heat capacity depends on:

mass of an object

chemical composition of the object

define specific heat capacity

amount of heat needed to raise the temperature of 1g of a substance by 1'C

specific heat capacity of water

4.184 J/g'C

define molar heat capacity

amount of heat needed to raise the temperature of 1 mole of a substance by 1'C

what does each letter represent?

q=MCAT

q- heat

m- mass

c- specific heat

AT- change in temperature (final - initial)

what does -q mean compared to q?

-q heat loss

q heat gain

define calorimity

precise measurement of heat flow into and out a system

heat released by the system = ?

proved by law of conservation of energy

heat released by the system = heat absorbed by the surroundings

define calorimiter

insulated device used to measure absorption or release of heat

final temp of system = ?

final temp of system = final temp of the surrondings

define enthalpy

the heat constant of a system at constant pressure

AH

heat of a reaction

q system

q surrondings

q system

q system- AH

q surrondings- MCAT

q system- AH= -qsurrondings = -MCAT

negative enthaply means..

exothermic

positive enthalpy means...

endothermic

how to write enthaply in thermochemical equations

the heat change can be written as a reactant or product

define molar Heat of fusion

heta absorbed by one mole of a solid substance when it melts at a constant temperature

AH(fus)

define molar heat of solidification

heat lost by one mole of a liquid substance when it solidifies

AH(fus) = -AH (solid)

what does the graph look like when a phase change is occurring?

plateau

define molar heat of vaporization

heat energy required to boil one mole of a substance at its boiling point

AH(vap)

defien heat of a solution

enthaply change caused by dissolution of 1 mole of a substance

AH(sol)

heat_of_fusion_number

6.02

heat_of_vaporization_number

40.7

define_hess's_law

if_you_can_add_two_thermochemical_equations_to_produce_a_final_equation,_the_sum_of_the_enthaply_of_those_equals_the_enthalpy_of_the_others

condensing_steam

exo

burning_alcohol

exo

evaporating_alcohol

endo

baking_potatoes

endo

how_to_find_molar_heat_capacity

use the specific heat to convert it to moles with grams on top

triangle H means what?

heat of formation

standered conditions are what?

25'C and 1atm

difference between calorie, specific heat, and molar heat

specific heat- 1g

calorie- 1g of water

molar heat- 1 mole

condensing

exothermic

C

nutrional calories