Flashcards in First principle of thermodynamics. Enthalpy. Deck (24):
Define thermodynamics and biological thermodynamics.
Thermodynamics is the study of conversions of energy exchanged between systems as heat and work.
Biological thermodynamics studies the general laws of energy conversion in living systems.
Define thermodynamic bodies and systems.
Thermodynamic bodies are a very large ensemble of particles.
Thermodynamic systems are a set of thermodynamic bodies exchanging energy.
What are the 3 types of thermodynamic systems?
Open- exchange both matter and energy with the environment
Isolated- do not exchange matter and energy with the environment
Closed- exchange energy but not matter. with environment.
Define thermodynamic variables.
Properties characterising the thermodynamic systems.
What are the 2 types of variables. Define them.
Extensive variables characterise the system as a whole. These variables can be calculated as the sum of the values of the variable for the separate subsystems that compose the system.
Intensive variables may have different values at different points in the system. It does not depend on the amount of substance in the system and it cannot be summed.
Define the thermodynamic state.
The set of instantaneous values of the thermodynamic variables of a system. The state changes if any variables changes its value.
What are the 2 types of thermodynamic states?
Equilibrium state- all variables remain constant over time and have the same values at all points in the system.
Non-Equilibrium state- the variables have different values at different points in the system that change over time.
Describe the graphic representation of thermodynamic states.
Equilibrium states can be represented by a point on a pressure-volume diagram(pV-diagram)
What is the equation of state?
a relationship between the variables of the equilibrium state, describing the properties of the system: f(p,V,T,n)=0.
Define the thermodynamic process.
The transition of a thermodynamic system from one state to another.
What are 2 types of thermodynamic processes?
Equilibrium process- the system is always in equilibrium state.. (Infinitely slow)
Non- equilibrium process- the system passes through non equilibrium states( Finite speed)
Describe the graphic representation of a thermodynamic process.
It can be represented by a curve on a pV- diagram.
What is a thermodynamic potential?
A variable of a thermodynamic system whose changes depend on the initial and final states only. It does not depend on the path taken.
Define internal energy.
It is a thermodynamic potential. It is the total potential energy associated with the inter-atomic and inter-molecular forces and the kinetic energy of the thermal motion of the atoms and molecules in the thermodynamic system. Does not depend on the position and movement of the system as a whole.
It is a form of energy transfer which can described by changes of macroscopic system variables.
It is a form of energy transfer by changing the microscopic thermal motions of particles.
Explain energy changes.
Performing work changes the potential, kinetic or internal energy of a thermodynamic system.
Heat exchange on alerts internal energy.
What is the first principle of thermodynamics?
Amount of heat (s)*Q transferred to a thermodynamic system is used to increase the internal energy of the system by dU and to perform work (s)*A on the environment: (s)*Q=dU+(s)*A.
When a system changes its volume at constant pressure, the quantity Q is a thermodynamic potential - enthalpy H
(s)*Q=dU+ p.dV = dH
Define Hess' law.
The thermal effect Q if a chemical reaction does not depend on the path of the transition form the reactants to the products. It only depends on the enthalpy differences between products and reactants.(Hb-Ha)
What are the application of Hess's law?
It holds true for metabolic processes.
It can be used for calculation of energy content of foods and the calculation of thermal effect of complex biochemical cycles.
What is a source of energy for the human body?
The body can use chemical energy from food released at its oxidation. This energy can be used to produce ATP molecules. Hydrolysis of ATP produces of energy for the body to use for work.
What are the 4 types of work in the body?
Chemical, mechanical, osmotic and electrical.