Chem Vocab Unit 6

energy

the capacity to do work

work

a directed energy change resulting from a process

kinetic energy

the energy produced by a moving object

radiant energy

solar energy

thermal energy

the energy associated with the random motion of atoms and molecules

chemical energy

stored within the structural units of chemical substances

potential energy

energy available by virtue of an object’s position

law of conservation of energy

the total quantity of energy in the universe is assumed constant

system

the specific part of the universe that is of interest to us

surroundings

the rest of the universe outside of the system

isolated system

cannot exchange mass or energy with the surroundings

closed system

can exchange energy

open system

can exchange mass and energy with the surroundings

exothermic process

any process that gives off heat (system→ surroundings)

endothermic process

any process that absorbs heat (surroundings→ system)

thermodynamics

the scientific study of the interconversion of heat and other kinds of energy

state of a system

the values of all relevant macroscopic properties (composition, energy, temperature, pressure, volume, mass, length); all are important because they can have an effect on the outcome of reactions

first law of thermodynamics

energy can be converted from one form to another, but cannot be created or destroyed

enthalpy

used to describe heat changes taking place at constant pressure

enthalpy of a reaction

the difference between the enthalpies of the products and the enthalpies of the reactants

thermochemical equation

show the enthalpy changes as well as the mass relationships; just like a regular equation but with a delta H term usually at the end

specific heat (sometimes c or s)

the amount of heat required to raise the temperature of one gram of the substance by one degree Celsius (J/gC)

heat capacity (C)

the amount of heat required to raise the temperature of a given quantity of the substance by one degree Celsius (J/C)

standard enthalpy of formation

the heat change that results when one mole of a compound is formed from its elements in their standard states (1 atm, 25C)

standard enthalpy of reaction

the enthalpy of a reaction carrued out at 1 atm and 25C

Hess’s Law

when reactants are converted to products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps

heat of solution

heat generated or absorbed when a certain amount of solute dissolves in a certain amount of solvent