chem 2 chapter 5
temperature change
most substances expand as the temperature increases and contrast as the temperature decreases. this property is used to measure _________________ __________
suroundings
serves to either provide heat to the system or absorb heat from the system
energy
the capacity to supply heat or do work
kinetic energy
the energy that an object possesses due to its motion
law of conservation of energy
the law that states that energy cannot be created or destroyed but can be changed from one form to another. when one substance is converted into another, there is always an associated conversion of one form of energy into another.
not correlated
The spontaneity of a process is ________ _______________ to the speed of the process.
exothermic process
a chemical reaction or physical change that releases heat
calorimeter
a device used to measure the amount of heat involved in a chemical or physical process. allows for the accurate determination of heat involved in chemical processes.
exothermic
a negative value for H in deltaH=deltaU+PdeltaV.
endothermic
a positive value for H in deltaH=deltaU+PdeltaV
endothermic process
a reaction or change that absorbs heat
specific heat capacity (c)
also known as a substance's specific heat. it is the quantity of heat required to raise the temperature of one gram by a substance of one degree celsius(or kelvin). c = q/m(delta T). it depends only on the kind of substance absorbing or releasing heat.
expansion work
also known as pressure volume work. it occurs when a system pushes back the surroundings against a restraining pressure, or when the surroundings compress the system.
heat of combustion
also known as the standard enthalpy of combusion (deltaH^deg. _c). the enthalpy change when 1 mole of a substance burns (combines vigorously with oxygen) under standard state conditions.
q=mc(deltaT)
an equation that determines the amount of heat entering or leaving a substance. used if you know the mass of the substance and its specific heat and the temperature change
endothermic
an example of an __________________ process is a cold pack. when the substances in the cold pack are brought together, the resulting process absorbs heat, leading to the sensation of coldness.
entropy (S)
change in heat energy at a given temperature in a reversible process. measures the number of ways to distribute energy in a system. S=qrev/T. "state of disorder of a system"
first law of thermodynamics
deltaU=q+w. this law shows that the internal energy of a system changes through heat flow into or out of a system (positive q is heat flow in, negative q is heat flow out) OR work done on or by the system (work is positive if it is done on the system and negative if it is done by the system)
potential energy
energy an object has because of its relative position, composition, or condition.
enthalpy (H)
energy change due to pdv work. (q=U + pdv)
stored
energy is ________ in a substance when the kinetic energy of its atoms or molecules is raised, resulting in a higher thermal energy. when kinetic energy is lost, the intensity of the atoms/molecule's movements decreases and thus the kinetic energy decreases.
out of
energy is transferred ___ __ a system when heat is lost from the system or when the system does work on its surroundings.
into
energy is transferred ______ a system when it absorbs heat (q) from the surroundings or when the surroundings do work on the system. both processes increase the internal energy of the wire, which is reflected by an increase in the wire's temperature.
internal energy decreases (delta U<0)
heat flows out of a system and work is done by the system.
heat flow
increases the thermal energy of one body and decreases the thermal energy of another body. _________ _______ will occur until two bodies at different temperatures are at the same temperature.
thermal energy
is the kinetic energy associated with the random motions of atoms or molecules
heat capacity (C)
is the quantity of heat (q) a body of matter absorbs or releases when it experiences a temperature change of 1 kelvin. C = q/(Tfinal - Tinitial). it is determined by both the type and amount of substance that absorbs or releases heat.
internal energy (U)
is the total of all possible kinds of energy present in a substance (all the energy is consisting of heat and work) in a system.(U=q+W). the _________ ______ of a system can be changed by heat flow and work.
work (w)
the process of causing matter to move against an opposing force
chemical thermodynamics
the science deals with the relationships between heat, work and other forms of energy in the context of chemical and physical processes.
system
the substance undergoing the chemical or physical change
heat (q)
the transfer of thermal energy between two bodies at different temperatures
state function
the value of a ________ ____________ depends only on the state that a system is in, and NOT how the state is reached. internal energy is an example of this function.
q(substanceW) = -q(substanceM)
this relationship displays that the heat lost by one substance (W) is equal to the heat gained by another (M) in the same system. The negative sign shows that the two substances are opposite in direction of heat flow (gain or loss).
thermochemical equation
used to represent both the changes in matter and energy. in this type of equation, the enthalpy change of the reaction is shown (deltaH) as a positive or negative number and this number represents the amount of heat associated with the reaction involving the number of moles of reactants and products as shown in the chemical equation.
thermal equilibrium
when one substance that is hotter (substance M) comes in contact with a less hot substance (substance W) and they interact with heat flowing from M to W until they are both at the same temperature. qsubstanceM + qsubstanceW = 0 (shows that ALL the heat transfer occurs just between the two objects and none is lost to external forces)
pdv
work done due to change in volume against constant pressure. (expansion or contraction)
internal energy increases (delta U>0)
work done on the system and heat flows into the system.
