AP Chemistry Chapter 8 - Thermochemistry

potential energy

energy possessed by an object because of it’s position, composition, or condition

kinetic energy

energy possessed by an object because of it’s motion

thermal energy

energy associated with the random motion of atoms and molecules

chemical energy

potential energy stored within chemical bonds in a substance

do fast moving molecules feel hot or cold

hot

do slow moving molecules feel hot or cold

cold

what is heat

the transfer of thermal energy between two bodies at different temperatures

what direction does heat flow

from hotter object to colder object

system

substance undergoing the chemical or physical change

in HCl + NaOH what is the system

H+, Cl-, Na+, OH-

in HCl + NaOH what are the surroundings?

the water surrounding the ions

what happens to the flow of heat in an endothermic process

from the surroundings to the system

is q positive or negative in an endothermic process

+

does endothermic absorb or release heat

absorbs

does an exothermic process absorb or release heat

release

what is the direction of heat flow in an exothermic process

from the system to the surroundings

is q negative or positive in an exothermic reaction

-

how many calories to J/kj

4.184J

how many kcal to j/kj

4.184 kj

what does 1 cal do to 1g of water

raises 1 degree celcius

what is heat capacity

amount of heat absorbed or released by a body of matter when it experiences a temeprature change of 1C

what variable is heat capacity

C

what units is heat capacity

J/degrees C

what is specific heat capacity

the amount of heat needed to raise the temperature of one gram of a substance by 1 degree celcius

what are the units of specific heat

J/g degrees c

Fe has a lower c than water. So, if they absorb the same amount of heat, which will have a greater temperature change?

Fe

What is a calorimeter for

measure the amount of heat and direction of flow in a process

what is the surroundings in a calorimetry equation

water

what happens when thermal equilibrium is reached

the system and surroundings will be at the same final temp

is q reaction equal to the negative or positive q calorimeter?

negative

if temperature of surroundings increases, is it exo or endothermic?

exothermic

if the temeprature of surroundings decreases, is it exo or endothermic?

endothermic

what do you have to assume in a coffee-cup calorimeter

all heat evolved from the reaction is absorbed by the water

what is the difference in calculating the dissolution of a solid in water in a coffee cup calorimeter problem

you use the total mass of the solution

when do you need to use a bomb calorimeter

releases a large amount of heat or uses gasses

is the delta t of the calorimeter equal to, greater than, or less than the delta t of water?

equal to

if the amount of water in the calorimeter is not specified, what do you do?

omit qwater from the equation

what equation does a bomb calorimeter use

-[(ccal x deltat) + (mcdeltatwater)]

what is enthalpy

the heat flow at constant pressure

what is the change in enthalpy ( delta H)

the change in heat flow at constant pressure (delta H = q)

is delta h porportional to the coefficients shown

yup

what is pressure in standard state

1 bar

what is the concentration of dissolved species in standard state

1 M

is it exothermic or endothermic if delta h is -

exothermic

is it exothermic or endothermic if delta h is +

endothermic

what are the ways to calculate delta h Rxn

calorimetry, hess’s law, delta h rxn = sum of delta h products - sum of delta h reactants

what is the movement from solid to liquid phase called

fusion

what is the movement from liquid to gaseous state called

vaporization

what is the movement from gas to liquid called

condensation

what is the movement from liquid to solid called

solidification

what is the movement from gas to solid called

deposition

what is the movement from solid to gas called

sublimation

are condensation, solidification, and deposition exo or endothermic

exothermic

are fusion, vaporization, and sublimation exo or endothermic

endothermic

how to solve how much heat is required to convert ice to water vapor at a certain temp

mcdeltat for heating ice, ndeltah for melting ice, mcdeltat for heating water, ndeltah for boiling water, mcdeltat for heating steam, add up all of the qs

if t surroundings increases is the reaction exo or endothermic

exothermic

if t surroundings decreases is the reaction exo or endothermic

endothermic