Chemistry 254 - Core Test
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19 Terms
Energy
A systems capacity to do work
Work
Force causes displacement and a net energy change in a system
Heat
Quantity of energy that flows across the boundary between system and surroundings as a result of a temperature gradient.
Open system
The system can exchange matter and energy with its surroundings
Closed system
Can exchange energy but not matter with the surroundings
Isolated system
Cannot exchange matter or energy with its surroundings
Intensive properties
value doesn’t change depending on the state of the reaction (temperature, density, etc.)
Extensive properties
Value does change depending on the state of the system (e.g. volume, mass, etc)
State function
A function/property of a system that only depends on its current thermodynamic state, not the path it took to get there (e.g. enthalpy. entropy, internal energy).
Path function
A function/quantity whose value depends on the specific sequence of steps/path taken to transition from its initial to final state (e.g. heat, work).
Isobaric
A state of constant pressure
Isochoric
A state of unchanging volume
Isothermal
A state of unchanging temperature.
First law of thermodynamics
energy cannot be created or destroyed, only transformed (dU = q + w)
Second law of thermodynamics
The total entropy of a system is always increasing and never decreasing
Enthalpy
Thermodynamic property of a system defined as the sum of a systems internal energy (u) and the product of its pressure(P) and volume (V). H = U + PV
Hess’s Law
The total enthalpy of a chemical reaction is the same, regardless of whether it occurs in one step or many, provided the initial and final are the same.
Heat capacity
The amount of heat energy required to raise the temperature of a given object or substance by one degree (Celsius or Kelvin).
Specific versus Molar Heat capacity
Specific: C = Q/mdT The energy needed to raise the temperature of 1g of a specific substance by 1 degree.
Molar: C = Q/ndT The energy needed to raise the temperature of 1 mole of a substance by 1 degree.