chemistry unit 1 semester 2

endothermic

absorb energy

endothermic equation

energy + reactants → product

exothermic

releases energy

exothermic equation

product + energy → energy

calorimetry

measurement of energy in a chemical or physical process

heat capacity

amount of heat required to raise the temperature one degree

specific heat capacity

amount of heat required to raise the temperature one degree in one gram

a calorie is equal to

4.18 J

calorimeter

device used to measure heat absorbed

extensive

depends on the amount of matter in a sample

intensive

depends on the type of matter in a sample

heat capacity units

J/°C, J/K, cal/°C, cal/K

heat capacity is what type of property

extensive

specific heat capacity units

J/g • °C, J/g • K, cal/g • °C, cal/g •

specific heat capacity is what type of property

intensive

what is needed to raise the temperature of a substance

energy

energy transfer equation

q = mCpΔT

q

heat gained or lost

m

mass

C_p

specific heat

ΔT

change in temperature

first law of thermodynamics

−q_metal = q_water

formula for heat gained/lost

q = cmΔT

heat exchange equation

−c_m m_m ΔT_m = c_w m_w ΔT_w

bomb calorimetry

technique used to measure the heat of combustion of a substance

heat of reaction

energy gained or lost during a chemical reaction

heat of combustion

energy gained or lost during a combution reaction

food calorie

kilocalorie

calorimetry is used to determine the energy content of

food

calorimetry equation

C₆H₁₂O₆ + 6(O₂) → 6(CO₂) + 6(H₂O) + 2.8 MJ

energy

ability to do work or cause change

joule (J)

the SI unit of energy

kinetic energy

energy associated with movement

work and kinetic energy equation

work = force x distance

more kinetic energy

more work that can be done

potential energy

energy based on position

gravitational potential energy

energy based on height and mass

mechanical energy

sum of kinetic and potential energy

other types of mechanical energy are

graviational potential energy and elastic potential energy

thermal energy

kinetic energy of particles in a system

thermal energy is based on

mass and temperture

temperature

average kinetic energy of particles in a substance

higher energy means

more kinetic energy

electromagnetic energy

energy related to electric and magnetic fields

examples of electromagnetic energy include

visible light, x rays, radio waves, electrical energy

chemical energy

energy stored in chemical bonds

chemical energy is a form of

potential energy

law of conservation of energy

energy cannot be created or destroyed

open system

system that can exchange matter and energy

closed system

system that can exchange only energy

energy transfermation

change in energy from one form to another

enthalpy

measure of energy in a thermodynamic system

hess’ law

regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes

H

state function

hess’s law equation

∆H1 + ∆H2 + ∆H3 = ∆H

reverse equation

reverse sign on ∆H_rxn

multiple equation by coefficient

multiply ∆H_rxn by the same coefficient

vertical axis

enthalpy

endothermic reaction

upward arrows

exothermic reaction

downward arrow

length of arrow

magnitude of enthalpy change

thermal energy of a substance

kinetic energies of molecules

temperture is low when

thermal energy is low

thermal energy is high

when temperature is high

heat

transfer of kinetic energy between fast and slow molecules

heat moves from

high to low kinetic energy

heat flows via

conduction

heat flows from

faster to slower molecules

bonds and reactants contain

potential energy

reactants

high energy

products have

low energy

state function

value that depends on the state of the substance

enthalpy of formation

energy absorbed or released when a pure substance forms

enthalpy of formation units

kJ/mol, kcal/mol

ΔH_f

enthalpy of formation

standard state

natural state of an elemental at 1 atm and 25°C.

ΔH_f for a pure element in its standard state

0 kJ/mol

enthalpy of reaction

energy absorbed or released during a chemical reaction

ΔH_rxn negative

exothermic

ΔH_rxn positive

endothermic reaction

thermochemical equation

chemical equation that shows thee state of each substance involved and the energy changes

enthalpy of combustion

enthalpy of reaction for a combustion reaction

ΔH_comb

enthalpy of combustion

enthalpy of combustion units

kJ/mol, kcal/mol

a calorimeter is used until

one temperature is reached

which statement is true for most chemical reactions?

an energy change occurs during the breaking and forming of bonds

what must occur for conduction to happen?

one must have higher kinetic energy than the other

what energy is directly related to the average kinetic energy of particles

thermal energy

positive enthalpy

endothermic

negative enthalpy

exothermic