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25 Cards in this Set

  • Front
  • Back
the ability to do work or produce heat

2 basic forms:
- PE (potential energy
- KE
potential energy
energy due to the composition or position of an object

potential energy of a substance depends upon:
- its composition
- the type of atoms in the substance
- the number and type of chemical bonds joining the atoms
- the way the atoms are arranged
law of conservation of energy
in any chemical reaction or physical process, energy can be converted from one form to another, but it is neither created nor destroyed
chemical potential energy
the energy stored in a substance b/c of its composition
the energy that is in the process of flowing from a warmer object to a cooler object

measured through the flow of energy and the resulting change in temp
a measurement of heat (metric)

Def: the amount of heat required to raise the temp of 1 g of pure water by 1 degree Celsius

1 (nutritional) Calorie = 1,000 cal or 1 kcal
the SI unit of heat and energy

1 cal = 4.184 J
specific heat
(of any substance) the amount of heat required to raise the temp of that substance by 1 degree Celsius

Unit: J/(g degrees C)

each substance has its own specific heat b/c different substances have different compositions
q (heat absorbed or released) =
q = c X m X change in temp

c = specific heat of substance
m = mass of substance (g)
change in temp = Tfinal - Tinitial (degrees C)
an insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process

- reactions occur at a constant pressure
the sutdy of heat changes that accompany chemical reaction and phase changes
the specific part of the universe that contains the reaction or process you wish to study
everything in the universe other than the system
the system + the surroundings
the heat content of a system at constant pressure

- you can't measure the actual energy or enthalpy of a substance, but you can measure the change in enthalpy
enthalpy (heat) of reaction
the change in enthalpy for a reaction-- the heat absorbed or released in a chemical reaction

= Hproducts - Hreactants


= Hfinal - Hinitial
process in which the system ABSORBS thermal energy from the surroundings

products have more energy than reactants

change Hrxn is positive

energy added is in the REACTANTS
process in which the system RELEASES thermal energy to the surroundings

products have less energy than the reactants

change Hrxn is negative

energy added is in the PRODUCTS
process in which the system ABSORBS energy (not neccessarily thermal) from the surroundings

energy added is in the REACTANTS
process in which the system RELEASES energy (not necessarily thermal) to the surroundings

energy added is in the PRODUCTS
thermochemical equation
a balanced chemical equation that includes the physical states of all reactants and products and the energy change, usually expressed as the change H

nature of reaction can be written as subscript of change H
enthalpy (heat) of combustion
the enthalpy change for the complete burning of one mole of the substance
standard conditions
1 atm pressure
298 K (25 degrees C)
indicated by the 0 superscript on changes in enthalpy
molar enthalpy (heat) of vaporization
the heat require the vaporize 1 mole of a liquid

endothermic-- positive

for water: = 40.7 kJ/mol
values for condensation are the same but with opp sign
molar enthalpy (heat) of fusion
the heat required to melt one mole of a solid substance


for water: 6.01 kJ/mole
values for solidification are the same but with opp sign