Chemistry - Ch 5 Flashcards
(51 cards)
Thermodynamics
the study of energy and its transformations; from Greek therme dynamis (heat power)
Thermochemistry
energy changes involving heat
Energy
the capacity to do work or to transfer heat
Work
the energy used to cause an object with mass to move against a force; w = force times distance
Heat
the energy used to cause the temperature of an object to increase; energy transferred from a hotter object to a colder one
Kinetic energy
the energy of motion; Ek = 1/2 mass times volume squared
Potential energy
arises when a force operates on an object by virtue of its position relative to other objects; Ep = mass times gravitational constant (9.8m per second squared) times height of the object relative to some reference height
Force
any kind of push or pull exerted on an object; F = mass times gravitational constant, 9.8m/s^2
Electrostatic potential energy
arises from the interactions between charged particles; Eel = k (constant of proportionality = 8.99 x 10^9 J-m/C^2 times the electrical charge on the two interacting objects, Q1 & Q2) divided by the distance separating them
Joule
SI unit for energy; 1 J = 1kg-m^2/s
calorie
non SI unit; =4.184 J; not the same as the nutritional Calorie (capitalized); 1 Cal = 1000 cal = 1kcal
System
the portion of the universe we single out for study; may be open, closed, or isolated
Surroundings
everything else that is not the system
Closed system
can exchange energy but not matter with its surroundings
Isolated system
one in which neither energy nor matter can be exchanged with its surroundings (ex. insulated thermos)
First Law of Thermodynamics
Energy is conserved; it can neither be created nor destroyed
Internal energy
sum of all the kinetic and potential energies of all its components
Change in internal energy
Delta E = E final - E initial; positive answer = system has gained energy from its surroundings; negative = system has lost energy to its surroundings; Delta E = q (heat added to or liberated from the system) plus w (work done on or by the system)
Endothermic
when a process occurs in which the system absorbs heat (endo = into)
Exothermic
process in which the system loses heat (exo = out of)
State function
a property of a system that is determined by specifying the system’s condition or state, in terms of temperature, pressure, etc.; the value of a state function depends only on the present state of the system, not on the path the system took to reach that state
Pressure-volume work (P-V work)
the work involved in the expansion or compression of gases (w = - P times the change in volume of the system)
Enthalpy
thermodynamic function that accounts for heat flow in processes occurring at constant pressure when no forms of work are performed other than P-V work; from the Greek, enthalpein, “to warm”); H (enthalpy) = E (internal energy) plus pressure times volume; a state function; extensive property
Change in enthalpy
change in internal energy plus the product of the constant pressure times the change in volume (Delta H = Delta E + P times Delta V); heat gained or lost at constant pressure
