Thermochemistry Flashcards
what are thermodynamics?
the science of the relationship between heat and energy
what is thermochemistry?
study of the quantity of heat or energy absorbed or evolved during a reaction
what is energy?
the potential or capacity to do work
what is kinetic energy?
the energy of motion
what is potential energy?
energy available to do work
what is a system?
the substance or mixture of substances under study in which a change occurs
what are the surroundings?
everything in the vicinity of the thermodynamic system
what is the first law of thermodynamics?
the law of conservation of energy
-energy may be converted from one form to another, but the total quantity of energy remains constant
what is the equation for internal energy?
ΔH=w+q
w- energy from work
q- energy from heat
what is an extensive property?
property that depends on the amount of substance
what is a state function?
property of a system that depends only on its present state. which is determined by variables such as temperature and pressure, and is independent of any previous history of the system
what is work?
energy transfer that results in an object moving through a field of force
what is heat? what variable is it represented by?
energy transfer between a thermodynamic system and its surrounding that results from a temperature difference
-q
when is q positive
if the heat is absorbed by the system (heat is added)
when is q negative?
if the heat is evolved by a system (heat is subtracted)
what is an endothermic process? how will the reaction vessel feel in this type of reaction? what sign is on q?
-chemical reaction or process in which heat is absorbed by the system
-vessel will feel cold
-q is positive
what is an exothermic process? how will the reaction vessel feel? what is the sign on q?
-chemical reaction or process in which heat is evolved y the system
-vessel will feel hot
q is negative
what is enthalpy?
extensive property that can be used to obtain the heat absorbed or evolved in a chemical reaction
what is enthalpy of reaction?
the change in enthalpy for a reaction given temperature and pressure
what is the equation for enthalpy of reaction?
ΔH= H(final)-H(initial)
what is freezing point?
temperature at which a pure liquid changes to a crystalline solid
what is melting point?
temperature at which a crystalline solid changes to a liquid
what is heat of fusion?
heat needed to melt a solid
what is heat of vaporization?
heat needed to vaporize a liquid
what is a thermochemical equation?
chemical equation for a reaction (including phase labels) and enthalpy of reaction which is written directly after the equation
what is heat capacity (Cp)?
quantity of energy needed to raise the temperature of an object by 1°C (at constant P)
what is specific heat (cp)?
quantity of energy required to raise the temperature of 1 g of a substance by 1°C (at constant P)
what is the equation for calorimetry?
-q=mcpΔT
what is the equation for specific heat?
-J/(g*°C)
