Chapter 5 | Energy Changes in Chemical Reactions
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29 Terms
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thermochemistry
the branch of chemistry that studies the energy changes in chemical reactions
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energy
the ability to do work (to make things move). It is the driving force of most chemical reactions
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kinetic energy
energy of motion/movement (of either atoms or molecules). It's directly related to the type of motion and the speed at which the atoms or molecules are moving.
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what are the three types of molecular motions?
vibration
rotation
translation
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potential energy
chemical energy stored in the bonds between atoms in a molecule
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temperature
temperature is the average kinetic energy of the particles in a substance. It tells how fast the particles in a substance, in average, are moving
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thermal energy
the sum of ALL kinetic energies of the particles. The thermal energy in an object depends on
number of particles
speed of particles
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what is the second law of thermodynamic
when two objects are in thermal contact, heat is always transferred from the object at higher temperature to the object at a lower temperature until the two objects are at the same temperature
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what is “heat”
the transfer/flow of thermal energy from a HOT object to COLD object
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what is a system
refers to all the chemical components that are involved in a chemical reaction, the reactants, products and whatever solvents they are in
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what are the systems that we study?
open, closed and isolated
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what is specific heat capacity (c)?
the amount of energy needed to increase the temperature of one gram of a substance by one degree Celsius - it is a physical property of a substance
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what is bond energy?
bond energy is the measure of bond strength
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how is bond energy determined?
determined by measuring the energy required to break the atoms involved in a molecular bond into free atoms
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what is another name for bond energy?
bond dissociation energy
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to break bonds, is energy added or released?
added
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to form bonds is energy released or added?
released
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what is enthalpy
the total energy of a system (kinetic energy + potential energy)
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what is ΔH?
it is the change in the enthalpy (energy) of a system
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what type of reaction is ΔH negative?
exothermic (net loss of energy)
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what type of reaction is ΔH positive?
endothermic (net gain of energy)
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for an exothermic reaction is the ΔH written on the product or reactant side for a thermochemical reaction?
product side
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for an endothermic reaction is the ΔH written on the product or reactant side for a thermochemical reaction?
reactant side
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what is molar enthalpy ΔHm
the enthalpy change of exactly one mole of a substance undergoing a change
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what is reaction enthalpy ΔHrxn
the total (net) enthalpy change of a reaction, for any given amount
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what is the unit for molar enthalpy?
KJ/mole
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what is the unit for reaction enthalpy?
KJ
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what is a calorimeter?
a device used to measure heat of a reaction
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what is the standard molar enthalpy of formation?
the change in enthalpy energy when 1 mole of a compound is formed directly from its elements in their most stable state at SATP
Note 
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