Concepts of Thermodynamics -ALL NOTES Flashcards
What is potential energy?
-Stored energy
What are examples of potential energy?
-Raised weight, stretched rubber band, charged battery
What are examples of kinetic energy?
-Boiling water, desk lamp, buzzing bee
What is kinetic energy?
-Energy of moving objects
What is thermodynamics?
-The science of energy interconversion
What is an isolated system?
-An isolated system cannot exchange energy or matter with its surroundings
What is a closed system?
-A system where mass cannot transfer but energy can
What is an open system?
-An open system can exchange both energy and matter with its surroundings
What is the zeroth law of thermodynamics?
-If two systems are in thermal equilibrium with a third system the two original systems are in thermal equilibrium with each other
What is the first law of thermodynamics?
-Energy can not be created or destroyed- only transformed from one form to another
What is the equation for the conservation energy?
-deltaU= Q-W
What does it mean if the Q is positive in the first law of thermodynamics ?
-Heat is added to the system so is an endothermic process
What does it mean if the Q is negative in the first law of thermodynamics ?
-Heat is released from the system so exothermic process
What is an SI unit?
-International System of Units equal to a joule or cal/kcal
What is 1 calorie?
-Heat needed to raise the temperature of 1 gram of water 1oc at standard pressure?
What is heat capacity?
-Amount of heat required to raise a substances temperature by 1 kelvin
What is specific heat capacity?
-Amount of heat required to raise 1 gram of a substance by 1 kelvin
What is the symbol for heat capacity?
-C
What is the symbol for specific heat capacity ?
-Cs
What is enthalpy?
-The measurement of energy in a thermodynamic system
What is the equation for enthalpy?
-deltaH = deltaE + delta(PV)
What can you assume about enthalpy equation in cells?
What happens to enthalpy in an endothermic process?
-
What happens to enthalpy in an exothermic process?
-
What is the second law of thermodynamics ?
-The universe is always moving towards maximum disorder
What is entropy ?
-Measure of disorder
What is the third law of thermodynamics?
-At absolute zero (0K) the entropy of a perfect, crystalline substance is zero
Why does entropy equal 0 at absolute zero?
-There is a perfect crystalline structure so all vibrations and atomic movements stop
What temperature is absolute zero in degrees Celsius?
-273.15 oc
What does G stand for?
-Gibbs free energy
What is Gibbs free energy?
-Energy available to do work and the spontaneity of a reaction
What does H stand for?
-Enthalpy (KJ mol-1)
If delta G is negative is the reaction spontaneous?
-Yes, in a forward reaction only
If delta G is zero is the reaction spontaneous ?
-Yes, at equilibrium, can proceed in either direction
If delta G is positive, is the reaction spontaneous ?
-No, unless coupled with an energetically favourable reaction
What is free energy of formation?
-The free energy change which results from 1 mol of substance prepared from its elements at standard temperature and pressure
How do you calculate free energy of formation?
-Delta G of formation of products minus delta G formation of reactants
What is the standard enthalpy change of a reaction?
-The heat transferred by a chemical reaction or process under standard conditions
What is bond dissociation energy?
-The enthalpy change per mol in the gas phase when a bond is broken
What does D stand for?
-Bond dissociation enthalpy
Is bond dissociation enthalpy positive or negative?
-Positive as bond breaking is an endothermic process
What is the standard entropy change of a reaction?
-The difference in standard entropy between the products and reactants of a system ubnder standard conditions
If a reaction is at equilibrium, what happens at E on the graph?
-G rises if the reaction proceeds in either direction
What does K stand for?
-The composition of a reaction mixture when it comes to equilibrium
What are the features of using K?
-Used in heterogenous reactions, must be associated with a specific temperature and equation of the reaction
What is Q?
-Measures the composition of the reaction mixture as the reaction progresses, not at equilibrium
If K is more than Q, what reaction proceeds?
-Forward
If K is less than Q what reaction proceeds?
-Reverse
If K=Q what reaction proceeds?
-both-at equilibrium
What is Le Chatelier’s principle ?
-When a change is made to a system in dynamic equilibrium, the system responds to minimise the effect of the change
