Thermodynamics, basics of thermodynamics B.Sc Second Year Biotechnology

1. Thermodynamics: Part1

2. Thermodynamics can be studied under
following headings-
Definition
System
Macroscopic properties of system
Thermodynamic State
State Variable and Functions
Thermodynamic Equilibrium

3. Definition of Thermodynamics
It is the branch of physical science
that deals with the relations between
heat and other forms of energy (such
as mechanical, electrical, or
chemical energy), and, by extension,
of the relationships between all
forms of energy.(1)
1
Biological thermodynamics is the
quantitative study of the energy
transductions that occur in or
between living organisms, structures,
and cells and of the nature and
function of the chemical processes
underlying these transductions.(2)
2

4. System  A thermodynamic system (or simply ‘system’) is
a quantity of matter of fixed identity, around
which we can draw a boundary (see Figure).
 It is a definite macroscopic region or space in
the universe, in which one or more
thermodynamic processes take place.
 The boundaries may be fixed or moveable.
Boundaries distinguish one system from rest of
the universe. Work or heat can be transferred
across the system boundary. Everything outside
the boundary is the surroundings.(3)
 Such a thermodynamic system is usually
referred to as control volume as it would posses
a volume and would also contain a definite
quantity of matter.
 System, surroundings and boundary constitute
the universe.(4) A specified part of the universe
which is under observation is called the system

5. Types of System
There are three mains
types of system:
open system,
closed system and
isolated system.

6. Types of systems All these have been described below
 1) Open system: The system in which
the transfer of mass as well as energy
can take place across its boundary is
called as an open system.
 Example of open system: Water
heated in an open container –
Here, heat is the energy transferred,
water is the mass transferred and
container is the thermodynamic
system. Both heat and water can pass
in and out of the container.
 All physical and chemical properties
taking place in our daily life are open
systems because these are
continuously exchanging matter and
energy with the surroundings.

7. Types of systems
 Closed system:
 A closed system allows only energy (heat and work) to pass in and out
of it.
 It does not allow mass transfer across its boundary.
 Example : water heated in a closed vessel. Here only energy can pass
in and out of the water.
Closed
system
No mass transfer
Energy outEnergy in

8. Types of systems
 Isolated system:-
 An isolated system does not interact with its surroundings. It does not
allow both mass and energy transfer across its boundary. It is more
restrictive.
 In reality, complete isolated systems do not exist. However, some
systems behave like an isolated system for a finite period of time. The
following image illustrates an isolated system.

9. Macroscopic properties of the System
 Thermodynamics deals with matter in terms of bulk (large
number of chemical species i.e. atoms, molecules or ions)
behavior. The properties of the system which arise from
the bulk behavior of matter are called macroscopic
properties.
 Macroscopic properties can be divided into two types
 Extensive properties
 Intensive properties

10. Extensive properties & intensive
properties
 The properties of the system whose value depend upon the amount or
size of the substance present in the system are called extensive
properties and the examples are-:mass , volume , surface area,
internal energy, enthalpy, entropy, free energy, heat capacity etc.
 The properties of the system whose value is independent of the
amount of substance present in the system are called intensive
properties and the examples are-: temperature, pressure, viscosity,
surface tension, dielectric constant, specific heat capacity, vapor
pressure, refractive index etc.

11. Thermodynamic state & State Variables
 For thermodynamics, a thermodynamic state of a system is its condition at a
specific time, that is fully identified by values of a suitable set of parameters
known as macroscopic properties, state variables, state parameters
or thermodynamic variables.
 Examples of state variables are-temperature , pressure, volume and
composition etc.
 If any of the macroscopic properties of the system changes, the state of the
system is also said to change. Thus the state of the system is fixed by its
macroscopic properties.
 For describing a system, it is not necessary to specify the value of all state
variables. For any system ,a certain minimum number of variables is sufficient
to define its state because the other variables become automatically fixed
and have definite values.

12. State functions
 A state function is a property that describes a particular state whose
value depends only upon the state of the system and is independent
of the path taken to reach this state. Mass, pressure, density, energy,
temperature, volume, enthalpy, entropy, Gibbs free energy and
chemical composition are all examples of state functions in
thermochemistry.
 Both path and state functions are often encountered in
thermodynamics.

13. Path and path functions
 Heat and work are not the state functions of the
system. Heat and work, unlike temperature, pressure, and volume
etc., are not intrinsic properties of a system. They have meaning only
as they describe the transfer of energy into or out of a system.
 Heat and work are two examples of path functions . These cannot be
defined for a state (you cannot say a system has an amount of work at
a specific set of conditions, only that it does a certain amount of work
to get from one state to another, via a specified path).
 Path functions depend on the route taken between two states.(6)

14. Path of thermodynamics
The diagram below shows two possible ways of getting
from State 1 to 2 . The work done on the two paths are
different if we consider the area beneath the curve.

15. Thermodynamic Equilibrium
 A system is said to be in thermodynamic equilibrium if its
macroscopic properties do not change with time.
 The Initial state of the system corresponds to the starting state of the
system in equilibrium before any type of interaction with the
surroundings.
 In the final state the system attains equilibrium after interaction with
the surroundings.
 The state function gives the difference in the property of the initial
state and the final state.
 Interaction with the surroundings means the transfer of energy matter
or both.

16. References
1. https://www.livescience.com › Tech
2. https://en.wikipedia.org/wiki/Biological_thermodynamics
3. http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node11.h
tml
4. http://mechteacher.com/thermodynamic-system/
5. https://www.brighthubengineering.com/thermodynamics/3733-wh
6. https://isaacphysics.org/concepts/cc_state_and_path_functions6.
7. https://www.quora.com/What-is-the-significance-of-enthalpy

17. References
1. https://www.livescience.com › Tech
2. https://en.wikipedia.org/wiki/Biological_thermodynamics
3. http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node11.h
tml
4. http://mechteacher.com/thermodynamic-system/
5. https://www.brighthubengineering.com/thermodynamics/3733-wh
6. https://isaacphysics.org/concepts/cc_state_and_path_functions6.
7. https://www.quora.com/What-is-the-significance-of-enthalpy