This document discusses the fundamental concepts of heat, temperature, and heat transfer, highlighting definitions, principles, and the various methods of heat transfer: conduction, convection, and radiation. It explains the laws governing heat exchange, the specific heat capacity of substances, and how impurities affect the melting and boiling points of materials. Key temperature scales and conversion formulas are also detailed, providing essential knowledge for understanding thermal dynamics.

1. HEAT
BY
SYED AMJAD HUSSAIN
M.Sc. Dpt.
QCHP Licensed
Diploma in football medicine
Certified orthopedic manipulative sports therapist

2. OBJECTIVES
• At the end of this chapter students able to identify
General principles.
What is heat.
What is Temperature
Scales of temperature and conversions.
Heat capacity.
Specific heat capacity
Law of heat exchange.
Heat transfers.
Modes of heat transfers.
Physiological and therapeutic effects of heat.

3. General principles
SoLID
Atoms, molecules
closely packed.
They vibrate about their
equilibrium position
LIQUID
Atoms, molecules have
greater amplitude.
Atoms have greater
speed because of
increased in temperature
move randomly.
E.g.: boiling of water
GAS
Atoms, molecules wider
space and larger
distances.
Heat causes more motion
so the atom become
further apart.
E.g.: CNG

4. Heat
• Definition
Transformation of a energy from an hot body to a cold body
due to their temperature difference, when they are in
thermal contact.
• Units
S.I: joule
CGS:CALORIE(cal).1 Cal=4.18J

5. Temperature
• Definition
The physical property which determines the quantity and
direction of heat flow between two bodies in thermal contact is
called temperature.
Or
Measure of level of the heat
Or
Degree of hotness and coldness of a body
Units
kelvin
Celsius degree
Fahrenheit degree

6. Scales of temperature
Celsius
scale
•
Freezing
point
=
0c
•
Melting
point
=
100c
Fahrenheit
scale
•
Freezing
point
=
32F
•
Melting
point
=
212F
Kelvin
scale
•
Freezing
point
=
273k
•
Melting
point
=
373k

7. Conversions of one scale
to another
Celsius to
Fahrenheit
F = 9/5 C+32
Fahrenheit to
Celsius
C = 5/9 (F-
32)
celsius to kelvin
Kelvin to celsius
TK=TC+273
TC=TK-273

9. • Temperature of a normal human body is 98.6F this
temperature into Celsius is?

10. Law of heat exchange
• “Heat lost by hot bodies is equal to the heat gained by
cold bodies”
• Expression
• Heat loss = heat gain
• If the right hand is immersed in hot water and left hand is immersed
in cold water then both hands placed in tap water it feels cold to the
right and hot to the left.

11. Heat capacity
• Definition
The amount of heat required to raise the temperature of an
object by a unit degree is called heat capacity.
Expression
If certain mass of substance absorbed a small amount of heat “delta Q”
for raise in temperature “delta T” heat capacity as’
c’= delta Q / delta T
Unit: j/k

12. Specific Heat capacity
• Definition
• The amount of heat required to raise the temperature of
1 kilogram of a substance by 1 degree K is called specific
heat capacity
• Expression
• If mass “m” of a substance absorbs small amount of heat delta “Q”
c = deltaQ / m*delta T
• unit
j/kg.k
Specific heat of water = 4.2 j/kg/k

13. Heat Transfers
• Heat transfer one body to another through three ways :
1. Conduction
2. Convection
3. Radiation

14. CONDUCTION
• Transferring of heat from place to place by kinetic
motion of atoms and molecules being passed from one to
next.
• Metals are the good conductors of heat and electricity.
• Thermal conductivity
• Jostling and knocking mechanism.

15. Example
Application of ice packs and hot packs

16. Convection
• Convection is the heat transfer mechanism that occurs in
a fluid due to gross movement of molecules within the
mass of fluid.
• Occurs in liquid and gases
• Circulation of blood all over the body

17. Example
• Sweating
• Evaporation

18. Radiation
• Heat may be transmitted by electromagnetic radiation
emitted from the surface of a body whose surface
temperature is above absolute zero.
• The rate of emission from a surface also depends on the
nature of the substance
• A perfect black body absorbs all the radiation

20. Transmission of Heat
• Conduction:
If one end of a solid metal rod is heated, the energy added causes an
increased vibration of molecules. This is transmitted and thus, heat is
conducted from area of high temperature to area of low temperature. For
example, metals.
• Convection:
It takes place in fluids. If one part of a fluid is heated, the kinetic energy of
the molecules in that part is increased, they move further apart and this part
becomes less dense. As a result it rises, displacing the more dense fluid
above which descends to take its place. The current produced is called
convection current.
• Radiation:
Heat may be transmitted by infra-red electromagnetic radiation. As a
substance is heated, it causes the electron to move to the higher-energy
shell. As it returns to its normal shell, the energy is released as a pulse of
infra-red electromagnetic energy

21. Effect of impurities on
melting and boiling points
• Impurities lowers the melting point and increase the
boiling point.

22. Impurities decreasing
melting point
• The solid phase of pure chemical is in in a stable crystal
lattice structure.
• When an impurity is added, it weakens the original
crystal structure due to its different shape and size.
• This makes it easier to break up the crystal with less force
i.e. the now impurity containing structure will need less
melting point to melt than the original chemical.

23. Impurities increasing
boiling point
• The presence of impurities decreases the number of water
molecules available to be vaporized during boiling.
• Hence more heat will now be required to boil the same
solution that was boiling at a lower temperature prior to
adding impurities.