Prof' Vinod Kallur

1
1
Prof. Vinod Kallur Chemical Engineering
Department R V College of Engineering, Bangalore
2
1
After the session you will be able to

• define thermodynamics
• define system, surroundings, and process
• classify the systems
• distinguish between state and path functions
• distinguish between intensive and extensive
  properties

3
2
THERMODYNAMICS
Thermo heat Dynamics - moving

• It deals with moving energy from one region to
  the other confirming to the law of conservation
  of energy.

• Work is a form of energy

It is a study of heat and work interaction with
the system.
When piston and cylinder containing gas is
heated, we expect certain changes. What are they?
4
3
w
How to bring the original conditions?
What is the net effect?
Work input and heat output
Q
5
4
This experiment establishes the equivalence
between heat and work. Work and heat are similar
and additive terms with the same units.
This experiment was done by Joule who is a
pioneer in this field.
Heat and work inter-conversion happens through an
agent called system.
In such a case how system will behave during this
conversion?
If we know all this we will be able to design a
process that has maximum conversion.
6
5
System
We need to fix our focus of attention in order to
understand heat and work interaction. The body or
assemblage or the space on which our attention is
focused is called system. The system may be
having real or imaginary boundaries.
Balloon attached to a tin, A chamber in which a
reaction is taking place.
Surroundings
This is defined as everything other than the
system. This idea of surroundings gets formulated
the moment you define the system.
7
6
Closed system
No exchange of mass between the system and
surroundings
Energy exchange with the surroundings may or may
not exist.
Mass of the system is constant
e.g., gas in piston and cylinder arrangement,
Liquid water and its vapor contained in a
closed vessel.
Open system
There will be mass exchange between system and
surroundings
Energy exchange with the surroundings may or may
not exist.
e.g., Boiling water in an open vessel.
8
7
Isolated system
Thermally isolated No heat transfer across the
boundary
Mechanically isolated The boundary is rigid
Completely isolated No exchange of mass and
energy with the surroundings.
Properties
Variables such as pressure, temperature, volume,
mass are Properties. A system will have a single
set of all these values.
List of properties of a system is exhaustive.
9
Extensive properties
8
The properties that depend upon amount contained
in the system are called extensive properties.
e.g., volume, mass
Intensive properties
The properties that are independent of amount
contained in the system are called extensive
properties.
e.g., pressure, temperature, density.
10
State of a system
9
It is defined as a condition of the substance
constituting the system.
They have same set of intensive properties such
as pressure, temperature and heat capacity etc
and hence said to be in the same state.
Even some properties such as viscosity, density
surface tension will have same values.
11
10
State of a system
What are the densities of these gas samples?
They are indistinguishable.
12
11
Heat
It is defined as energy in transit.
It is not appropriate to talk of heat content of
a body or heat contained in a substance.
Cloud
Rain
water
Energy in transit (heat) as soon as it ceases to
flow, it becomes internal energy.
13
12
Work
This is also form energy in transit.
Work is considered being done only during the
process.
14
13
This integral is also the area under the curve p
vs. V between the points 1 and 2.
2
a
1
15
14
Work depends upon the process and the path taken.
Thus the work is said to be path function.
What is the pressure at 2 if 2 is reached from 1
by the curved path and by 1-a-2?
What about volume?
They are same regardless of path.
Such quantities are called state functions.
16
15
Let us recapitulate what we discussed.
Meaning of thermodynamics
System closed, open and isolated
properties intensive and extensive
State and path functions