Exam 3 Chapter 5 Flashcards
heat
heat (q): transfer or thermal energy between two bodies at different temperatures
thermal energy
kinetic energy associated with the random motion of atoms and molecules
temperature
quantitative measure of “hot” or “cold”
Energy
the capacity to supply heat or do work
Exothermic Process
change that releases heat
ex: combustion reaction using a torch
Endothermic Process
reaction or change that absorbs heat
ex: a cold pack
calories (cal)
amount of energy required to raise one gram of water by one degree C (or 1 degree K)
Joule (J)
amount of energy used when a force of 1 newton moves an object 1 meter
SI unit of heat, work, and energy
1 calorie =
4.184 Joules
heat capacity (C)
the quantity of heat (q) a body of matter absorbs or releases when it experiences a temperature change of 1 degree C (or 1 degree K)
C = q/deltaT
specific heat capacity (c)
quantity of heat required to raise the temperature of 1 gram of substance by 1 degree C (or 1 degree K)
c = q/(mdeltaT)
q = (specific heat)(mass of substance)*(temperature change)
calorimetry
way to measure the amount of heat involved in a chemical process
system
the substance(s) undergoing the chemical/physical change
surroundings
all other matter apart from the system, including the measurement apparatus, that serves to provide heat to the system or absorb heat from the system
calorimeter
device used to measure the amount of heat involved in a chemical or physical process
qreaction + qsolution =
0
qreaction =
-qsolution
bomb calorimeter
used to measure the energy produced by reactions that yield large amounts of heat and gaseous products, such as in combustion reactions
1st Law of Thermodynamics
change in internal energy of a system (U) is equal to the heat and work of the system
*Law of Conservation of Energy
deltaU = q + w
Enthalpy (H)
the sum of a system’s internal energy (U) and the product of its pressure and volume
is a state function
H = U+ PV
Hess’s Law
if a process can be written as the sum of several stepwise processes, the enthalpy change of the total process equals the sum of the enthalpy changes of the various steps
*this is valid because enthalpy is a state function
