Thermochemistry Flashcards
What is thermochemistry?
Thermochemistry is the science concerned with the amount of heat released or absorbed during chemical and physical changes.
What is energy?
Energy is the capacity to supply heat or do work.
What is potential energy?
Potential energy is the energy an object has because of its relative position, composition, or condition.
What is kinetic energy?
Kinetic energy is the energy an object possesses because of its motion.
What is thermal energy?
Thermal energy is kinetic energy associated with the random motion of atoms and molecules.
What is heat?
Heat is the transfer of energy between two bodies at different temperatures.
What is an exothermic process?
An exothermic process is a change that releases heat.
What is an endothermic process?
An endothermic process is a reaction or change that absorbs heat.
What is a calorie?
A calorie is the amount of energy reqired to raise 1 gram of water 1 degree Celsius.
What is a joule?
A joule is the amount of energy used when a force of 1 newton moves an object 1 meter.
What is the relationship between calories and joules?
1 calorie = 4.184 joules
What is heat capacity?
The heat capacity (C) of a body of matter is the quantity of heat (q) it absorbs or releases when it experiences a temperature change (ΔT) of 1 degree Celsius.
C = q / ΔT
What is specific heat capacity?
The specific heat (c) of a substance is the quantity of heat required to raise the temperature of 1 gram of a substance 1 degree Celsius.
c = q / mΔT
What is internal energy?
Internal energy (U) is the total of all possible kinds of energy present in a substance.
What is the relationship between internal energy, heat, and work?
ΔU = q + w
What is expansion work?
Expansion work occurs when a system pushes back the surroundings against a restraining pressure, or when the surroundings compress the system.
What is a state function?
A state function is a property depending only on the state of the system, and not the path taken to reach that state.
What is enthalpy?
Enthalpy (H) is defined as the sum of a system’s internal energy (U) and the mathematical product of its pressure (P) and volume (V).
H = U + PV
What is the formula for enthalpy change at a constant pressure?
ΔH = ΔU + PΔV = qp, where qp is the heat of reaction at a constant pressure.
What is standard enthalpy of combustion?
Standard enthalpy of combustion (ΔH°C) is the enthalpy change when one mole of a substance burns (combines vigorously with oxygen) under standard conditions (25ºC and 1 atm).
What is standard enthalpy of formation?
Standard enthalpy of formation (ΔHºf) is an enthalpy change for a reaction in which 1 mole of a pure substance is formed from free elements in their most stable states under standard conditions.
What is Hess’s law?
Hess’s law states that if a process can be written as the sum of several stepwise processes, the enthalpy change of the total process equals the sum of the enthalpy changes of the various steps.
What is the formula for determining the enthalpy change of a reaction if the corresponding enthalpies of formation of the reactants and the products are available?
ΔHreaction = Σn • ΔHºf (products) – Σn • ΔHºf (reactants)
