Chapter 5 Chem

thermodynamics

the science of heat and work

kinetic energy

energy associated with motion

potential energy

results from an object's position i.e. energy possessed by a ball held above the floor

law of conservation of energy

energy can neither be created nor destroyed - total energy of the universe is constant

system

an object, or collection of objects, being studied

surroundings

include everything outside the system that can exchange energy and/or matter with the system

thermal equilibrium

eventually two objects become the same temperature

exothermic process

energy is transferred as heat from a system to its surroundings. The energy of the system decreases, and the energy of the surroundings increases

endothermic process

the opposite of an exothermic process. Energy is transferred as heat from the surroundings to the system, increasing the energy of the system, decreasing the energy of the surroundings

joule

energy quantities

calorie

old measurement of energy. 1 = 4.184 joules

Specific heat capacity

the energy transferred as heat that is required to raise the temperature 1 gram of a substance by one kelvin

q= c x m x delta T

equation used when energy gained or lost as heat when a given mass of a substance is warmed or cooled

q1 + q2 + q3 = 0

law of conservation of mass: in an isolated system the sum of the energy changes within the system must be zero and transferred only as heat

heat of fusion

energy transferred as heat that is required to convert a substance from a solid at its melting point to a liquid

heat of vaporization

energy transferred as heat to convert liquid at its boiling point to a vapor

sublimation

change directly from a solid to a liquid

first law of thermodynamics

(delta U) is the sum of energy transferred as heath between the system and its surroundings (Q) and the energy transferred as work between the system and its surroundings (w)

internal energy

internal energy in chemical system is the sum of the potential and kinetic energies of the atoms, molecules, or ions in the system

state function

no matter how you go from reactants to products in a reaction, the reaction is always the same

standard enthalpy change

the pure, unmixed reactants in their standard states have formed pure, unmixed products in their standard states

standard state

an element or compound is defined as the most stable form of the substance in the physical state that exists at a pressure of 1 bar and at a specific temperature

calorimetry

measurement for the energy evolved or required as heat in a chemical or physical process

Hess's Law

states that if a reaction is the sum of two or more other reactions then it is also for the sum of those reactions