Chapter 2.1: Heat, Work, & Energy Flashcards
What is thermodynamics?
study of the energy changes involved in physical and chemical processes
What are some examples of physical processes?
heating and cooling a substance, phases changes, changes in physical parameters (volume, pressure of a gas)
What is thermochemistry?
thermodynamics relating to heat flow, or change In heat energy, occurring in chemical reactions
How does the food “calorie” compare to the energy unit “calorie”?
food calorie (Cal) is equal to 1000 calories
How does 1 calorie compare in joules?
1 cal = 4.184 J; (energy to raise the temperature of 1g of water by 1ºC)
1 Cal = 4.184 kJ (amount of energy needed to raise the temperature of 1 kg of water by 1ºC)
What is heat flow?
transfer of thermal energy in a process
In what direction does heat flow?
from warmer object to the cooler object until thermal equilibrium is reached
What is an open system?
system exchanges matter and heat with surroundings
What is a closed system?
system exchanges heat with surroundings
What is an isolated system?
system exchages nothing with surroundings (no heat or matter)
What is energy?
the capacity to do work
What is work?
product of force and distance
What is calorimetry?
experimental way to measure enthalpy change
What is q(cal)?
heat in calorimeter assembly (container, lid, thermometer)
what is q(rxn)?
reactants/reaction
what is q(sol)?
solvent/solution
How is temperature change measured in a reaction?
temperature change of calorimeter and solution
- increase in heat of surrounding = decrease heat in reaction
- decrease in heat of surrounding = increase heat in reaction
What is simple calorimetry?
experiment occurs under constant pressure
- q(rxn) = ∆H(rxn) when H is enthalpy
What is thermal/heat energy?
energy transferred due to a temperautre difference between the system
What is kinetic energy?
energy associated with motion
What is potential energy?
stored energy possessed by a body due to position
What is chemical energy?
- type of potential energy
how is work related with pressure and volume?
w = -P * ∆V (in kPa L)
- work involved in the expansion or compression of gases
What an endothermic reaction?
heat gained/absorbed by system:
q(rxn) > 0
q(sol) < 0
What is an exothermic reaction?
heat lost/released by system:
q(rxn) < 0
q(sol) > 0
What is heat capacity (C) ?
heat needed to heat apparatus 1 degree ºC or ºK used for objects and each piece of apparatus
- used in q(Cal) = C ∆T
What is specific heat capacity (c)?
similar to heat capacity but consideres the mass of the substance
- heat needed to warm one mass unit (g or kg) of a substance by 1 degree
- in J/g K
- used in q(sol) = m c ∆T
What is the relationship between heat capacity and energy to increase temperature?
higher heat capacity = more energy needed to increase temperature
What is ∆T?
temperature change: T(final) - T(initial)
either both in Kelvin or Celcius
How is thermal equilibrium represented?
-q(lost) = q(gained)
- both objects reach the same temperature
What is an intensive/intrinsic property?
property that has the same value regardless of sample size (doesn’t depend on the amount of material)
What are intensive/intrinstic property examples?
temperature, MP, BP, density
What is an extensive/extrinsic property?
physical property what increases with sample size (depends on amount of material)
What are extensive/extrinsic property examples?
mass, volume, energy, enthapy, and entropy
What is a state function?
property whose value depends only on the current state of the system, but not how that state was reached (doesn’t depend on route taken, only depends on initial and final state)
What are examples of state functions?
volume, pressure, enthalpy
What is the first law of thermodynamics?
total energy of an isolated system is conserved
- no energy lost to surroundings and heat exchange only occurs within the system
- energy can be transferred from one part of the system to another, or converted from on form to another, but it cannot be created or destroyed
net change in heat = q(sys) = 0 = q(rxn) + q(cal) + q(sol)
What is internal energy (E)?
sum of all kinetic and potential energies of all atoms, ions, and molecules in a system
- extensive property and state function
What is meant by expansion of a gas?
the gas (system) is doing work on surroundings and value of w is negative
- work energy has been used so it has been removed from the system
what is mean by compression of a gas?
the surroundings are said to be doing work on the system, and the value of w is positive
- the system has gained work
When is w = 0?
when a process does not involved compression or expansion and there is not volume change (∆V = 0)
