Chapter 06: Thermochemistry Flashcards
Energy
The capacity of matter to do work
Work
w
w = F×d (work = force × distance)
The action of a force through a distance.
Heat
q
The flow of energy caused by a difference in temperature
Types of energy (4)
Kinetic energy (due to motion)
Thermal energy (associated with temperature)
Potential energy (due to position/composition)
Chemical energy (associated with positions of electrons and nuclei)
Heat v. Temperature
Transfer of thermal energy v. measure of thermal energy
Thermal equilibrium
Heat flows from matter with high temperature to matter with low temperature until both objects reach the same temperature.
Thermochemistry
Study of relationships between chemistry and energy
System
Specific part of the universe that is of interest in a study
Surroundings
Everything else with which the system can exchange energy
Open system
Mass & energy is exchanged
Closed system
ONLY energy is exchanged (not mass)
Isolated system
Neither mass nor energy is exchanged (no exchange at all)
Kinetic energy
KE = 1/2mv2
Directly portional to m and v
Units: kg×m2/s2
(half of mass × velocity squared)
1 J = ? KE
1 J = 1 kg×m2/s2
1 cal = ? J
1 cal = 4.184 J
1 Cal = ? cal
1 Cal = 1000 cal (or 1 kcal)
Exothermic reaction
Releases heat by transferring thermal energy from system to surroundings
Endothermic reaction
System gains heat from surroundings to react
Internal energy
E
Sum of KE + PE of all particles within a system
Change in internal energy
ΔE = Eproducts - Ereactants
State function
Function that depends only on intial and final conditions
First law of thermodynamics
Energy can be converted from one form to another, but it cannot be created nor destroyed
Total energy of universe is contant
Thus:
ΔEsystem = -ΔEsurroundings
and:
ΔE = q + w
*q (heat) is positive when energy is gained
negative when energy is lost
*w is positive when work is done ON the system
negative when work is done BY the system
Energy exchange
Accomplished through heat and work between system and surroundings
Pressure-volume work
Occurs when the force is caused by a volume change against an external pressure
w = -PΔV
work = the negative of external pressure × change in volume
work done = -w!