Chem Chp 7 Flashcards
Thermodynamics
study of energy, work, and heat
3 Laws Thermodynamics
- Energy cannot be created or destroyed only converted from one form to another
- Universe spontaneously tends toward increasing disorder or randomness.
- Disorder of a pure perfect crystal at absolute zero is zero
molecules and atoms are in constant random motion and
frequently collide with each other
average kinetic energy of the atoms or molecules ____ with increasing temperature
increases
Collisions with sufficient enrgy will
break bonds in molecules
when reactant bonds are broken
new bonds may be formed and products result
We can only measure change in energy
TRUE
System
process under study
surroundings
encompasses the rest of the universe
Heat
transfer of thermal energy to the surroundings
exothermic reaction
releases energy to the surroundings
energy to break bonds is less than the energy given off when the bond forms
Energy is product
endothermic reaction
absorbs energy from the surroundings
energy to break bonds is greater than the energy realeased, the reaction needs more energy
Energy is reactant
Enthalpy
Heat
Change in enthalpy
energy released is represented with a negative sign (exothermic)
energy absorbed is shown with a positive sign (endothermic)
Most but not all exothermic reactions
are spontaneous
Most but not all endothermic reations
are NOT spontaneous
Entropy
Measure of the randomness of a chemical system- Represented S
Reactions that are exothermic and whose products are more disorder will
occur spontanously
Endothermic reactions producting products of low entropy ill
not be spontanous
Free Energy
Delta G represents the combined contribution of the enthalpy and entropy values
pg 224
Calorimetry
measurement of heat energy changes
Calorimeter
device used for these measurements
Specific Heat
The number of calories of heat needed to raise the temperature of 1 gram of the substance 1 degree celsious
Heat equation
Q= ms x delta T x SH
