MCP 1 Chapter 1 Thermodynamics
Questions about the lecture 'From Molecular to Continuum Physics 1' of the RWTH Aachen Chapter 1 Thermodynamics
Questions about the lecture 'From Molecular to Continuum Physics 1' of the RWTH Aachen Chapter 1 Thermodynamics
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Lernkarten
What is the concept of thermodynamics? [3]
1. Phenomenological theory of matter
2. Relationship and conversions between forms of energy so-called thermodynamical systems (TS)
3. Macroscopic system (MS) → TS
What is the definition of the system?
Part of the universe
What is the definition of the surroundings?
Universe without the system
What is the definition of the boundary of a system?
Element which divides the system from its surroundings
Which boundaries exist? [7]
1. Open is the exchange of matter and energy
2. Close is the exchange of energy but not matter // Pot
3. Isolated is neither the exchange of energy nor mater // Thermoskanne
4. Permeable is the exchange of matter
5. Rigid is a system with no increasing volume [decrease?]
6. Adiabatic is a rigid wall with no exchange of energy or matter
7. Diathermic is a rigid wall with exchange of energy and matter
What is the definition of properties of a system?
Measurable macroscopic quantities of the system which can be intensive or extensive
What are examples for intensive properties? [3]
1. Pressure P
2. Temperature T
3. Density M/V
What are examples for extensive properties? [2]
1. Volume V
2. Mass M
What is the definition of a homogeneous system?
Equality of all intensive properties
What is the definition of a heterogeneous system?
The combination of homogeneous systems (so-called phases)
What is the definition of a system state? [2]
1. Set of values necessary for description which depend only on the current state
2. Path independence with exact differential
What is the definition of equilibrium of a state? [2]
1. State does not change over time // Steady
2. Is homogenous
What is definition of gas?
Collection of molecules or atoms in continuous random motion
What is the ideal gas?
Gas behaving in a universal way if sufficiently dilute
What is the perfect gas? [4]
1. Ideal
2. Chemically non-reactive
3. Always in thermodynamic equilibrium
4. Neglectable intermolecular forces
What is the law of the perfect gas?
P*V = n*T*R with Regnault constant R=8,314 J/K*mol
What are the parameters of gas? [4]
1. Volume V in m³
2. Pressure P=F/A in Pa // Direction of mass flow
3. Temperature T in K // Thermal state
4. Number of molecules n in mol
Which different units of pressure exist? [5]
1. bar is 10⁵ Pa
2. atm is 101325 kPa
3. Torr is 133,32 Pa
4. mmHg is 133,322 Pa
5. psi is 6,894757 Pa
What is the definition of the mechanical equilibrium?
Two gases in container with movable wall with higher/lower P will expand/compress to the mechanical equilibrium
What is the definition of °C?
C is K-273,15
What is the definition of the thermal equilibrium?
Two gases in container with diathermic wall with higher/lower T will flow to the thermal equilibrium
What is the zero law of temperature?
If A B and B C are in thermal equilibrium Then A C are in thermal equilibrium
What is the definition of the number of molecules n in mol? [2]
1. Mole is amount of substance that count as many entities as they are atoms in 12 g of carbon-12 // relative atomic mass is 12
2. Amount corresponds to Avogadro constant 6,022141129*10^23
What is the definition of work W? [2]
1. Achieve motion against opposing force // Expansion Delta V of gas pushes piston
2. Delta W = P*Delta V
What is the definition of heat? [3]
1. Temperature difference or thermal motion as energy transfer
2. In diathermic container heat restores the equilibrium
3. In isolated system temperature decreases/increases
What is the difference between work and heat? [2]
1. Work is organized molecular motion
2. Heat is disorderly molecular motion
What is the definition of an exothermic process?
Exothermic process releases energy into surroundings
What is the definition of an endothermic process?
Endothermic process acquires energy from surroundings
What is the definition of energy?
Capacity to do work
How does the energy of a system changes? [2]
1. Work is done to the system → energy increases
2. Work is done by the system → energy decreases
What is the definition of the internal energy U? [4]
1. Is extensive property and total energy of a system in J or kg*m²/s²
2. Changed by work, heat or adding/taking matter (isolated system)
3. State function means that change of U is change system state (DU = Uf-Ui with f final state and i initial state)
4. Proportional to temperature
What is the definition of molar interal energy Um? [2]
1. U = U/n +Um(T=0)
2. Intensive property of a system
What is the equipartition theorem?
In equilibrium energy is shared equally among all forms
What is the molecular interpretation of internal energy? [3]
1. Monatomic particles have three translational degrees of freedom // No rotational or vibrational
2. Ek = ½*mv_x² + ½*mv_y² + ½*mv_z² = 3*(½*k*T) with Boltzmann’s constant k=1,381*10^23 J/K
3. U = 3/2 *N*k*T = 3/2 * n*R*T with N = n*N_A and R = N_A*k
What is the definition of a system path?
1. Physical quantities for description of path between two states
2. Path dependence with inexact differential
What types of work exist? [5]
1. Expansion
2. Surface expansion
3. Extension
4. Electrical
5. Adiabatic
What is the definition of expansion work? [3]
1. dw = -F*dz or -p_ex*dV with dV=A*dz → w = -integral_Vi,Vf(p_ex*dV)
2. Free if p_ex is zero
3. w = -p_ex*dV if p_ex constant
What is the definition of surface expansion work?
dw = gamma*dSigma with surface tension gamma [N/m] and change in area dSigma [m²]
What is the definition of extension work?
dw = f*dl with tension f [N] and change of length dl [m]
