Theme 2- BASICS OF THERMODYNAMICS

Question 1

What is thermodynamics

Answer 1

-It is a discipline of physics, describing the laws of heat and thermal processes.
-Involves relationships between quantities characterizing the macroscopic
state of the thermal system and changes in these quantities in physical processes
associated with heat exchange between the system and its surroundings.
-Thermodynamics deals with the laws of conservation and conversion of energy
applicable to thermal processes

Question 2

Laws of thermodynamics

Answer 2

1st law of thermodynamics (energy conservation)
2nd law of thermodynamics
3rd law of thermodynamics

Question 3

1st law of thermodynamics

Answer 3

The increase of the internal energy of the system (ΔU) is equal to the sum of the work (W) performed by the surrounding bodies acting on the system and the heat (Q) transferred by the surrounding bodies to the system. U  Q W
If the system receives energy:
W > 0 and/or Q > 0; ΔU > 0
If the system transmits energy: W <0 and/or Q <0; ΔU <0

Another formulation of the 1st law of thermodynamics: It is not possible to construct a
“Perpetuum mobile” of the first kind (i.e. a machine that cyclically repeats a process
with only initial energy).

Question 4

2nd law of thermodynamics

Answer 4

Heat can’t spread spontaneously from a colder place to a warmer one.

Another formulation of the 2nd law of thermodynamics: It is not possible to construct
a Perpetuum mobile of the second kind (i.e. a cyclically operating heat engine that
would only receive heat from a warmer body and perform as much work as the
received heat). This means that heat energy cannot be spontaneously (and completely)
transformed into mechanic work

Question 5

3rd law of thermodynamics

Answer 5

The entropy change of the system equals zero in any isothermal process taking place at an absolute zero temperature (in other words, it is not possible to reach an absolute zero temperature).

Question 6

Thermodynamic system

Answer 6

A body or group of bodies whose condition we are investigating. Quantities by which the state of the system is determined, e.g. pressure,
temperature, volume, and energy are state variables.

Question 7

al energy

Answer 7

A part of the internal energy of the body (or defined part of space), which is related to the disordered (thermal) movement of particles in the substance (in defined space).

Question 8

Temperature

Answer 8

-A thermodynamic (state) quantity that characterizes the ability of an object to receive heat spontaneously from another object.
-Temperature as a state quantity describes one of the thermodynamic parameters - thermal equilibrium or imbalance.
-The temperature units are °C or K or other. The following applies to the
conversion between the Celsius and Kelvin scales:
T= t 0 C + 273.15

Question 9

Heat

Answer 9

-Is the energy that is transferred in a certain form, can be exchanged between objects, or transformed from one to another form of energy or work.
-Heat (Q) is a change in the thermal energy of an object.
-The unit of heat (as well as energy) is joule
(J).
ΔQ =c.m. Δt where: ΔQ is the heat change; Δt (K) temperature increase; m (kg) is the
weight;
c (J/ kg.K) is the specific heat (material constant).