chapter 17 Flashcards
heat
energy that transfers from one object to another because of a temperature differnce between them
heat always flows from
a warmer object to a cooler one
thermochemistry
study of energy chances that occur during the chemical reactions and changes in state
chemical potential energy
the neergy stored in the chemical bonds of a substance
endothermic process
system gains heat as the surroundings cool down
exothermic process
the system loses heat as the surroundings heat up
system
the part of the universe on which you focus your attention
surroundings
include everything else in the universe, usually water
in an endothermic reaction, heat is a
reactant
in an exothermic reaction, heat is a
product
1 cal =
4.18 J
heat capacity
amount of heat needed to increase the temperature of an object exactly 1 degree celcius
specific heat
the amount of heat it takes to raise the temp of 1g of a substance 1 degree Celsius
specific heat of water
4.18
equation for specific heat
C = joules / mass (g) x delta T
calorimetry
precise measurement of the heat flow into or out of a system for chemical and physical processes
equation for calorimetry
-q = -(mass x specific heat x delta T)
enthalpy
the heat content of a system at contstant pressure
thermochemical equation
chemical equation that includes the enthalpy change
heat of reaction
enthalpy change for the chemical equation exactly how it is written
heat of combustion
heat of reaction for the complete burning of one mole of a substance
molar heat of fusion
heat sborbed by one mole of a solid substance as if melts to a liquid
molar heat of solidification
heat lost when one mole of a liquid solidifies at a constant temperature
hess’ law
you can add the heats of reaction if you add two or more thermochemical equations
standard heat of formation
change in ethalpy that accompanies the formation of one mole of a compound from its elements
