Basic thermodynamics Dr Vijaya Shastry, RJ COLLEGE, MUMBAI, INDIA

1. THERMODYNAMICS BASICS
By
DR VIJAYA SHASTRY Ph.D
CHEMISTRY DEPT
RJ COLLEGE
MUMBAI , INDIA

2.  The study of thermodynamics is concerned with the ways energy
is stored within a body and how energy transformations (involve
heat and work).
 One of the most fundamental laws of nature is the conservation
of energy principle which states that during an energy interaction,
energy can change from one form to another but the total amount
of energy remains constant.
 That is, energy cannot be created or destroyed.

3.  Thermodynamics is
 The science that examines the effects of energy transfer on
macroscopic materials systems.
 Thermodynamics predicts
 Whether a process will occur given long enough time
• driving force for the process
 Thermodynamics does not predict
 How fast a process will occur
• mechanism of the process

4.  A thermodynamic system, or simply system, is defined as a
quantity of matter or a region in space chosen for study.
 The region outside the system is called the surroundings.
 The real or imaginary surface that separates the system from
its surroundings is called the boundary. The boundary of a system
may be fixed or movable.
 Surroundings are physical space outside
the system boundary.

5. Thermal energy – a form of kinetic energy
characterized by randomness of motion at the
atomic and molecular level
Temperature – the degree or intensity of heat
present in a substance or object; the measure of
the hotness or coldness of a body

6.  THERMODYNAMICS is a branch of physics
concerned with the mechanical work,
pressure, temperature and their roles in
the transformation of energy.

7.  Natural Sources
› The Sun
› The Earth’s Interior
 Artificial Sources
› Chemical Action
› Electrical Energy
› Mechanical Energy
› Nuclear Energy

8.  THERMOMETER is any thermal sensor that
measures temperature.
 The lines of a thermometer are called
CALIBRATIONS.
 LIQUID-IN-GLASS THERMOMETER ROTARY
THERMOMETER, THERMOCOUPLE
THERMOMETER and LIQUID CRYSTAL
THERMOMETER are a few examples.

10.  In CELSIUS SCALE, the freezing point of
water is 0 while the boiling point is 100
degrees Celsius.
 In FAHRENHEIT SCALE, the freezing point
of water is 32 while the boiling point 212
degrees Fahrenheit.

11.  THERMAL ENERGY is the kinetic energy
characterized by the randomness of
motion at the atomic and molecular
levels of a body.
 HEAT is the quantity of thermal energy
absorbed or given-off by a body.
 TEMPERATURE is the measure of hotness
or coldness of a body.

12.  The change in internal energy of a closed system ∆U, will be equal to
the energy added to the system by heating the work done by the
system on the surroundings.
∆U=Q–W 1 st Law of
Thermodynamics
 Q is the net heat added to the system
W is the net work done by the system
∆U is the internal energy of a closed system.
**First law of thermodynamics is conservation of energy.

13. ISOTHERMAL PROCESS – process that carried out at constant
temperature
PV = constant
PV diagram for an ideal gas undergoing isothermal
processes

14. ADIABATIC PROCESS – An adiabatic process is one in which no heat is
gained or lost by the system. The first law of thermodynamics with Q=0
shows that all the change in internal energy is in the form of work.
PV diagram for an ideal gas undergoing isothermal
processes

15. ISOBARIC PROCESS – A process is one which the pressure is kept
constant.
ISOVOLUMETRIC PROCESS – A process is one in which the volume
does not change

16.  Second Law of Thermodynamics is a statement about which
processes occur in nature and which do not.
Heat can flow spontaneously from a hot object to a cold object;
heat will not flow spontaneously form a cold object to a hot object.
Q = mc ΔT =
mc (T2 – T1)
Q = quantity of heat transferred (J)
m = mass of the material (kg)
c = specific heat capacity (J/kg K)
T1= initial temperature (K or °C)
T2= final temperature (K or °C)
ΔT= temperature difference = T2 – T1

17. EXPANSION OF MATERIALS
“Materials expand as their thermal energy
increases.” → Thermal expansion
It is easier to open a tight bottle cap
by exposing it to heat!

18. “Materials contract as their thermal
energy decreases.”
EXPANSION OF MATERIALS UNDER 100°C
Materials Length of
(1 m in length) Expansion
Invar (alloy of Fe and Ni) 0.1 mm
Pyrex 0.3 mm
Platinum alloy 0.9 mm
Glass 0.9 mm
Concrete 1.0 mm
Steel 1.0 mm
Brass 2.0 mm
Aluminum 3.0 mm

19. THERMOSTAT
“The amount of expansion of a material
depends on the change in temperature.”
The device that regulates the temperature of a material is
called, a thermostat. It is usually consists of bimetallic strips e.g.
Brass (alloy of Cu and Zn) and Fe that are welded together. When the
Brass side is heated it expands and contracts when cooled → can
help turn on/off a device such as heaters.

20. HEAT TRANSFER
The study of the flow of heat within an
object or from one medium to another due to
their variation in temperature.
METHODS OF HEAT TRANSFER
• Radiation - energy is emitted in the form of
electromagnetic waves or subatomic particles e.g.
heat/warmth felt from a flame or bonfire sans
touching it, the heat from the microwave oven and the
heat from the sun.

21. 2. Conduction - heat energy transfer caused by direct
contact wherein heat travels from one molecule to
another. For example, exposing metal to a flame,
allowing an article to rest on a warm or hot object.
“Heat flows from a region of high concentration to a
region of low concentration.”
Legend:
Hot → Cold

22. 3. Convection - transference of mass or heat
within a fluid caused by the tendency of
warmer and less dense material to rise
producing air or fluid currents.
Air cools down,
Hot air rises
becomes dense
Air heats up and Cold air sinks
becomes less
dense

23. SPECIFIC HEAT
The amount of energy required to raise the
temperature of one kilogram (1 kg) of a
substance by one °C (1°C) or one Kelvin (1 K).
It is expressed in terms of Joules per kilogram-
Kelvin (J/kg·K) or Joules per kilogram degree
Celsius (J/kg·°C) or calorie per gram degree
Celcius (cal/g·°C) in which 1 cal = 4.186 J.

24. THERMAL CAPACITY
The amount of heat required to raise the
temperature of a substance by 1 degree (1°) and
is the product of its mass and specific heat.
ΔQ = mCΔT
Wherein,
ΔQ is change in heat expressed in terms of J
m is the mass of the substance in kg
C is the specific heat in J/kg·K
ΔT is the change in heat in K

25.  Heat naturally flows from high to
low temperature, but for
refrigerators and air conditioners do
work to accomplish the opposite to
make heat flow from cold to hot.

26.  Electrical Energy => Kinetic Energy => Heat energy
 When refrigerants change from vapor to liquid, heat is discharged.
 On the contrary, changing from liquid to vapor, heat is absorbed