Lec 25 Thermochem Flashcards
What is internal energy
Total energy of a system
U= PE+KE (on microscopic lvl)
What is the system
Part of the universe being studied
What is the surroundings
Anything not part of the system
What is the universe
System + surroundings
EVERYTHING
What is temperature
A measure of the average KE of molecules (thermal energy)
Can also be known as the quantity that determines direction of heat flow
Which way does heat flow when two objects are in thermal contact
From the hotter object to the colder object until they gain thermal equilibrium
Why are gasses good insulators?
Because heat flows better when there are more collisions, gases are always colliding
What is heat what are the units
Flow or transfer of energy due to temp difference
J or kJ
What is q
Heat that flows into a system from the surroundings
What happens if q is postive
-endothermic
-heat absorbed by system
- U increases
What happens if q is negative
-exothermic
-heat released by system
- U decreases
What is work
Force across a distance
When is work positive, what happens to U
When work is done on the system by surroundings
U increases
When is work negative, what happens to U
When work is done on surroundings by system
U decrease
What is U
Internal energy
What does it mean if somethings an extensive property
The thing depends on how much stuff you have
Ex. The amount of water L depends on how much water I have)
What does it mean when somethings intensive
Amount of it doesn’t matter
Ex if you cut a block in half the density is still the same although there is less block
What is a state function, what are examples
Any property where it’s value is only dependent of current state of the system, independent of history or path
Density
Entropy
Enthalpy
What aren’t state functions, why?
Q and W, their values depend on how the change/process is carried out
They are extensive properties
