The document discusses systems, surroundings, and various thermodynamic concepts. It defines a system as any part of the world under observation with a boundary separating it from its surroundings. Systems can exchange both energy and matter with surroundings (open), just energy (closed), or neither (isolated). The state of a system is defined by properties like temperature, pressure, and volume. The first law of thermodynamics states that energy is conserved and can change forms but not be created or destroyed. Internal energy depends on the state of the system, not the path to get there. Heat and work are path dependent terms related to changes in internal energy. Enthalpy accounts for pressure-volume work. Specific heat is the energy to raise 1g

1. Basic concepts 1
Physical chemistry
for Textile
6. Thermodynamics
L10: State of system, First law

2. Basic concepts 2
System and Surrounding
 Any part of the world
which is under our
observation is called a
system and whatever
around it is called
surrounding. The system
has a definite boundary
which separates it from
the surrounding.

3. System and Surrounding
 A bird is a system
which is separated
from its surrounding
by its skin and
fethers.
 It exchanges both
energy and matter
with its environment.
Basic concepts 3

4. System and Surrounding
 If earth is
considered as a
system,
everything around
its surrounding.
 It exchanges
energy with the
environment but
not matter.
Basic concepts 4

5. System and Surrounding
 A flask containing
some material can
also be considered as
a system where the
glass body of flask is
system boundary.
 Everything outside
the flask is it’s
surrounding.
Basic concepts 5

6. System and Surrounding
 Sometimes the
system may not have
a definite boundary.
For example: a cube
of dry ice. The dry ice
diffuses into the air
without melting at a
temperature of -78.5
°C.
Basic concepts 6

7. System and Surrounding
 Similarly,
naphthalene
converts directly
from solid to vapor
phase.
Basic concepts 7
What is the phenomenon by which a solid converts directly into vapor
without liquifaction?

8. Basic concepts 8
System and Surrounding
 Energy and or matter
may or may not
exchange between
system and
surrounding
depending on the
type of system
boundary.

9. Definitions of System
 Depending on the
properties of system
boundary the systems
may be divided in
three different kinds.
Open system
Closed system
Isolated system
Basic concepts 9

10. Basic concepts 10
Open system
 Open system is the
system in which both
energy and matter
can move across the
boundary of system.

11. Winch dyeing
 In an open
winch the
material can
move in or
out of it and
energy too.
Basic concepts 11

12. Basic concepts 12
Closed system
 Closed system is that
in which only energy
can cross the
boundary of system
but matter cannot.

13. Closed system
 The
boundary of
a closed
system may
expand.
Basic concepts 13

14. Jet dyeing
Basic concepts 14
 Jet is a closed
machine with high
pressure and
temperature.
Here no material
flows in or out of
the machine but
heat can flow in
and out.

15. Basic concepts 15
Isolated
system
 Isolated system the
system in which
neither matter nor
energy can cross the
system boundary.

16. Basic concepts 16
Comparison of systems

17. Basic concepts 17
State of a system
 State of a system is the condition of
the system defined by certain set of
properties. For instance the volume,
pressure and temperature of a
system defines a certain state of
that system. If for example the
pressure on a system is reduced,
the volume will increase and the
system is said to be in a new state.
 Similarly if the temperature of the
system is increased the volume will
increase and the state of system will
change.
 When the set of properties defining
the state of a system are known, the
system is said to be in a definite
state.

18. Basic concepts 18
Properties of state of system
 The properties which
determine the state of a
system are called state
properties.
 State properties such as
temperature, pressure and
volume have major
significance. However there
are other state properties also
such as it’s composition.
 If the pressure, temperature ,
volume or other state
properties of a system are
known then the system is said
to be in a definite state.

19. Properties of state of system
 A dyeing system consisting of
dye bath containing 10 kg of
aqueous dye solution and 1 kg
fabric at 25 °C at atmospheric
pressure is in a definite state.
 We raise the temperature to 60
°C and the system changes to
a new state.
 When the dye transfers to
fabric that is reactants are
consumed and products are
formed, again the state of
system changes.
Basic concepts 19

20. Law of conservation of energy
 This law states that the
total energy in the
universe is conserved.
That is, it cannot be
created or destroyed,
however, it can change
from form to the other.
20

21. Internal energy
 The internal energy of a
system is the sum of all types
of energy in it.
 When a system passes from
one state to another state,
there is a corresponding
change in the internal energy
of the system.
ΔE = E2 – E1
 E is called internal energy and
ΔE is the change in internal
energy.
21

22. Internal energy
 A system containing calcium oxide (CaO) and water
(H2O) has some internal energy in the form of chemical
energy at the beginning of reaction. As the reaction
proceeds and reactants change into Ca(OH)2, a large
amount of heat energy is evolved. As a result the
internal energy of the system reduces. The change in
energy can be calculated simply by subtracting the initial
state from final state.
22
CaO + H2O = Ca(OH)2 + heat

23. Internal energy – state function
 State functions are those properties of a
system which depend only on the state of
the system and not on the path they follow
to reach the final state.
 Since internal energy is a state function,
hence depends only on the state of the
system. Therefore any change in the
internal energy depends only on the initial
and final states of the system and is
represented by:
ΔE = E2 – E1
23

24. Internal energy – state function
 For instance, we consider the
following example:
If we have two identical
containers having equal
amounts of water in them.
 We heat one of the containers
to raise it’s temperature through
1˚C and simply stir the water in
other container so that it’s
temperature rises through 1˚C.
 At the end, the change in both
systems is exactly same and
independent of the fact how the
change was brought up.
24

25. Internal energy
 This change in
internal energy is
independent of the
path of change and
depends on the state
of the system.
25

26. Internal energy
 Therefore the internal energy of a system
depends on the state of the system and
not on the path or the way how it was
brought about, that is:
ΔE = E2 – E1
 The properties of a system which depend
on the state of the system and not on the
path are called state functions.
26

27. Path dependence - Work
 Those properties of a system which
vary with the path taken to change the
state of system are path functions.
 The work, for example, vary with the
path taken to reach the final state
27

28. Change of state
 When a
system
passes from
one state to
the other
state, it may
lose or gain
energy as
heat or
work.
CaO + H2O = Ca(OH)2 + (-ΔH)
In the above instance the
heat content of product is
less than the reactants.
NaNO2 + H2O = Na++NO-
2 +
(+ΔH)
In this example the heat
content of product is less
than the reactants.28

29. Change of state
 Consider a gas confined in
a cylinder with a movable
piston. Now some heat is
transferred from
surrounding to the system.
This absorption of heat
energy may trigger two
processes:
 1. It may increase the
internal energy of the
system.
 2. Some of the heat
absorbed may be
consumed in doing P
ΔV work against
external pressure.
q = ΔE + w
29

30. Change of state
 A dyeing bath is heated
from room temperature to
100ºC. What changes will
occur in the final state if it
is an open system?
 What if the temperature
of dyeing bath is raised to
30ºC only?
q = ΔE + w
30

31. Change of state
 In chemical reactions
if some gaseous
product is formed or
gaseous reactants
change to liquid
product work is done
by the system or on
the system.
HCl + Zn = ZnCl2 +
H2
HCl + H2O =
H3O++Cl-
31

32. Change of state
 Condensation of
water vapor?
 Changing of water
into steam?
Work done
on or by
the
system?
32

33. Relationship between internal energy, heat
and work
 The change in internal energy is given by
the equation:
q = ΔE + w
ΔE = q – w
Or = q – P ΔV
 There are certain conditions under which
heat and work terms become definite:
 Constant pressure and
 Constant volume
33

34. Enthalpy
 The term E + PV is called enthalpy or
heat content of the system and
represented by H, therefore:
H = E+PV and
qp = H2 - H1 = ΔH
34

35. The First law
 The first law of thermodynamics is
simply the statement of law of
conservation of energy, that is: The
energy cannot be created or
destroyed.
35

36. Specific heat
 If a system consists of 1g of a
substance and a definite
amount of heat is transferred to
it so that it’s temperature rises
by 1°C, the amount of heat thus
transferred is called it’s specific
heat.
The specific heat or specific
heat capacity of a substance is
the amount of heat required to
raise the temperature of 1 gram
of a substance by 1°C.
36

37. Heat capacity
Heat capacity of a system
is defined as the amount
of heat required to raise
the temperature of the
system by 1˚.
 The heat capacity of a
system is given by the
following equation:
C = specific heat x mass (g)
37

38. Heat capacity
 For e.g. if the temperature of
1000 kg of water is to be
raised by 1°C, the amount of
heat absorbed will be:
C = specific heat x mass (g)
= 1 cal/g °C x 1000 Kg x 1000
= 1000,000 cal/°C
= 1000 kcal/°C
38

39. Molar heat capacity
 If the system consists of 1
mole of a substance it is
called molar heat
capacity.
The molar heat capacity
is the amount of heat
required to raise the
temperature of 1 mole of
a substance through 1°.
39

40. Molar heat capacity
Find the mole of each of
following.
 Oxygen = ?
 Carbon dioxide = ?
 Methanol = ?
 Mole of ethanol = ?
 Mole of glycerine = ?
 Water = ?
 Copper = ?
 Iron = ?
Calculate the
molar heat
capacity of
each of these
from specific
heat data.
40

41. Heat capacity
 Since the heat capacity C may vary with
temperature, it is written in the form:
C = q/dT
 Here q is an infinitesimally small amount of
heat absorbed by the system when the
temperature is raised by dT degrees.
 Since q is an indefinite quantity unless
certain conditions are defined, hence, it is
normally defined at constant pressure or
constant volume.
41

42. Heat capacity at
constant pressure - Cp
 Heat capacity at constant pressure is
equal to rate of change of the energy of
the system with temperature at constant
pressure.
Cp = qp/dT
qp = ΔH
Cp = dH/dT
42

43. Heat capacity at
constant volume - Cv
 Heat capacity at constant volume is equal
to rate of change of the energy of the
system with temperature at constant
volume.
Cv = qv/dT
qv = ΔE
Cv = dE/dT
43

44. Difference of Cv and Cp
 In case of Cp, some of the
energy absorbed will be
consumed in doing work
against the surrounding and
rest of it will raise the internal
energy.
 However in case of Cv, no
work is done by the system.
 Hence for a similar system the
energy required in case of Cp
will be greater than in Cv.
44

45. Importance of thermal data
 We can calculate the
amount of heat
required to gain the
required temperature
of system of definite
properties.
 We can calculate the
cost of heating.
How the heat of
dyeing can be
calculated?
How the energy
cost of dyeing
can be
calculated?
45

46. Importance of thermal data
 Different materials
have different specific
heat capacity. Hence
two materials having
different specific heat
capacities on
absorbing the same
amount under the
same condition
achieve different
temperatures.
 Observe
temperatures of
different objects
placed in sunlight.
46
Wood
Iron body of a car
Water
A plastic bottle
Wool
Cotton
polyester

47. Importance of thermal data
 If cotton and polyester
fabrics are placed
under sun under the
same conditions, why
the temperature of
polyester rises above
that of cotton.
Why it happens
so?
 This is one of the
reasons why
wearing pure
polyester in hot
weather is
uncomfortable
while cotton is
more comfortable.
47

48. Problem 1
 Determine the heat capacity of 100 kg
of water in kJ/kg-K. The specific heat
of water is 1 cal/g. The conversion
factor to convert cal to Joule is 4.184.
 What difference in Cp and Cv for the
above system do you expect.
48

49. Problem 2
 If a piece of wood and that of iron of
same mass are put in environment
under the same condition, iron will
gain higher temperature than wood.
What is the reason of this
phenomenon.
49

50. Problem 3
 How many calories are required to
heat each of the following from 15 to
65 ˚C:
550 gram of water
1 kg of Polyester
1 kg of Nylon
1 kg of cotton
50

51. Which system?
 A classroom?  Open
 Closed
 isolated
Basic concepts 51

52. Which system?
 An open glass of
water kept on
table?
 Open
 Closed
 isolated
Basic concepts 52

53. Which system?
 A pressure cooker
with food inside?
 Open
 Closed
 isolated
Basic concepts 53

54. Which system?
 A water distillation
unit?
 Open
 Closed
 isolated
Basic concepts 54

55. Which system?
 The earth with its
atmosphere?
 Open
 Closed
 isolated
Basic concepts 55

56. Which system?
 A volcano with
magma inside it?
 Open
 Closed
 isolated
Basic concepts 56

57. Which system?
 A pod of peas?  Open
 Closed
 isolated
Basic concepts 57

58. Which system?
 A tomato?  Open
 Closed
 isolated
Basic concepts 58

59. Which system?
 A thermos?  Open
 Closed
 isolated
Basic concepts 59