Thermodynamics Flashcards
What are kinetic and potential energy? What are the different forms of energy it can be manifested in?
potential energy - can be considered stored energy
- intermolecular and intramolecular forces
- nuclear energy
kinetics energy -
- potential energy can be related in this form
- relates to objects in motion
- vibrational, rotational and translational
What is internal energy?
total combination of energies
- kinetic and potential
- accounts for all energy in and out of a system
What is a system? What are the different types of system?
refers to the object being studied
- energy can be transferred between the systems and its surroundings via the boundary
isolated system
- no energy or mass can be transferred to or from the surroundings
closed system
- energy can be transferred to or from the surroundings but not mass
open systems
- both energy and mass can be transferred to and from the surroundings
How can the energy of a closed system be transferred?
energy can be transferred to or from the surroundings as heat or work
heat = thermal energy, relates to the motion of the atoms and molecules, measured in calorie work = process used to directly move an object a certain distance against an opposing force, measured in joules
How can the change in internal energy of a system be measured?
caused by energy transfer via heat or work does
change in internal energy = work + heat
U = w + q
energy supplied TO the system as work and energy supplied TO the system as heat
What is work done for gaseous products?
expansion work
- system expands against the external pressure (container)
work done = (Pex) x change in volume
Pex = pressure against external system
change in volume = area force is acting on x height
What is an isothermal reversible expansion?
when an ideal gas expands without a change in temperature, its internal energy remains constant.
What is enthalpy?
thermodynamic quantity equivalent to the total heat content of a system
What is enthalpy change?
enthalpy change of a reaction = enthalpy of products - enthalpy of reactants
difference between the energy consumed to break bonds and the energy released when bonds are formed
What is the enthalpy of an endothermic and exothermic reaction?
endothermic reaction = change in enthalpy is greater than zero (positive)
- energy is put in for the reaction to occur
exothermic reaction = change in enthalpy is less than zero (negative)
- energy is released during the reaction
What is Hess’s Law?
change in enthalpy of a reaction = sum of enthalpy of products - sum of the enthalpy of reactants
multiply by the stoichiometric coefficients of each
What is the enthalpy of elements in their standard state?
enthalpy change of elements in their standard state is assumed to be zero
example - oxygen or carbon
What is bond enthalpies?
amount of energy required to break 1 mole of a particular bond
always positive
What is entropy?
a measure of the chaotic dispersal of either matter or energy
- entropy of an isolated system increases during a spontaneous change
How does entropy change across the states of matter?
molecules that are more organised and stable have less entropy
solid - lowest entropy
liquid
gas - highest entropy
