Dental related heat topic

1. HEAT

2. Temperature and its Measurements
Heat : Heat is a form of energy or Heat is defined as the total
energy of an object that has molecular motion inside it
or The flow of energy from a warm to a cooler object
Sources of Heat
There are many sources of heat. The main sources of
heat are
 Sun
 Chemical
 Electrical
 Nuclear

3. Temperature
Temperature is defined as the measure of the thermal energy of an object. Unit is
Kelvin (K) and the symbol is T
Thermometer - it is an instrument for measuring
the temperature of a system.
The thermometer is used to measure body temperature is
a clinical thermometer.
It consists of a bulb (mercury), kink, capillary tube, stem,
and glass tube.

4. Different types of Thermometric Scales and Thermometers
Scale
Lower Fixed
Point
Upper Fixed
Point
Celsius (°C) 0°C 100°C
Fahrenheit (°F) 32°F 212°F
Kelvin (K) 273.15 K 373.15 K

5. Pyrometers
 Pyrometers are devices used to measure high temperatures, typically
beyond the range of conventional thermometers.
 They are employed in various industries and scientific applications
where accurate temperature measurements of hot objects or
environments are essential.
 Pyrometers work based on the principle of detecting thermal
radiation emitted by an object.
 There are different types of pyrometers, and each operates on a
distinct principle.
Pyrometers find applications in various industries like
 Metallurgy: Monitoring the temperature of molten metal.
 Glass Manufacturing: Measuring the temperature of molten glass.
 Ceramics: Monitoring furnace temperatures.
 Power Plants: Measuring the temperature of boiler components.
 Astronomy: Determining the temperature of stars.

6. Optical Pyrometers
These pyrometers determine temperature by comparing the
brightness or color of the radiation emitted by the hot object to that of
a calibrated light source.
Two-wavelength optical pyrometers are commonly used, where the
intensity of the emitted radiation at two different wavelengths is
compared.
Types of Pyrometers
Infrared Pyrometers:
Also known as IR pyrometers, these devices measure the infrared
radiation emitted by a hot object.
They are non-contact instruments, making them suitable for
measuring temperatures of moving or hard-to-reach objects.
Radiation Pyrometers:
These pyrometers determine temperature by measuring the
total radiation emitted by an object, without distinguishing
between visible and infrared radiation.

7. Two-Color Pyrometers:
These pyrometers use the ratio of intensities at two
different wavelengths to eliminate errors caused by
variations in emissivity (the ability of a surface to emit
thermal radiation).
Fiber Optic Pyrometers:
Fiber optic pyrometers use fiber optic cables to
transmit thermal radiation from the target object to a
remote sensing location, allowing for measurements
in hazardous or hard-to-reach environments

8. Thermal Expansion of Solids, Liquids and Gases
Solid
•The particles of solid are always packed tightly.
•The gaps between the particles of a solid are very less and
therefore the compression of solid is tough.
•The shape and volume of a solid is fixed.
•Solid is rigid in nature, hence the particles of solid only
vibrate about their mean position and cannot move.
•Attractive force between the particles of solid is adamant.
•Example: solid ice, wood, sugar, rock, etc.

9. Liquid
•The particles of liquid are less tightly packed when compared
to solids.
•Liquids have the ability to take the shape of the container in
which liquids are kept.
•The particles of liquid have less space between them to move
so the compression liquids are difficult but not as in solid.
•The Volume of Liquid is fixed but the shape of Liquid is not
fixed.
•Rate of Diffusion in liquids is more as compared to solid.
•Example: water, milk, coffee, blood etc.

10. Gas
•The particles of gas are far from each other.
•The force of attraction between the particles of gases is
almost negligible and hence they can move
independently.
•The volume and shape of gas are not fixed.
•The particles of gas have more space between them to
move so the compression gases are easy.
•The rate of diffusion is more as compared to solids and
liquids.
•Example: air, oxygen, nitrogen, carbon dioxide, etc.

11. Thermal Expansion Types
There are three types of thermal expansions which we will learn.
1.Linear Expansion
2.Volume Expansion
3.Area Expansion
Linear Expansion
When the length changes because of heat then it is known as linear
expansion.
ΔL = α L0 ΔT
Here,
ΔL = Change in Length
α = Coefficient of length expansion
L0 = Original Length
ΔT = Difference in temperature
Coefficient of Linear Expansion is defined as rate of change of
length per unit temperature.
α =dL/dT Unit is C-1 or K-1

12. Area Expansion
When the area changes because of heat then it is
known as area expansion.
ΔA = β A0 ΔT
Here,
ΔA = Change in Area
β = Coefficient of area expansion
A0 = Original Length
ΔT = Difference in temperature
Coefficient of Area Expansion is defined as rate of
change of area per unit temperature.
β =dA / dT Unit is C-1 or K-1

13. Volume Expansion
When the volume changes because of heat then it is
known as volume expansion.
ΔV = γ V0 ΔT
Here,
ΔV = Volume Change
γ = Coefficient of volume expansion
V0 = Original Volume
ΔT = Difference in temperature
Coefficient of Volume Expansion is defined as rate
of change of volume per unit temperature.
γ = ΔV / Δ T Unit is C-1 or K-1

14. Charles Law
Charles law I : States that the volume of an
ideal gas is directly proportional to the absolute
temperature at constant pressure.
V ∝ T, at constant pressure
Charles’ law, also sometimes referred to as the
law of volumes
Charles law II : States that the pressure of
an ideal gas is directly proportional to the
absolute temperature at constant volume.
P ∝ T, at constant Volume
•In cold weather or in a cold
environment, helium balloons shrink.
•In winter, when the weather is cool,
the capacity of the human lung
decreases. This makes it more
difficult for the athletes to perform on
a freezing winter day, and it also
makes it difficult for people to go
jogging.

15. Boyle’s Law
Boyle’s law is a gas law which states that the
pressure exerted by a gas is inversely
proportional to the volume occupied by it when
temperature is kept constant.
P ∝ 1/V , at constant temperature
Boyle’s law is a gas law given by the Anglo-
Irish chemist Robert Boyle in 1662.
Ideal Gas Law
This law relates pressure, volume, number of moles or molecules and
temperature of gas .
The ideal gas law gives the relationship between these four different variables.
Mathematically Ideal gas law is expressed as,
PV = nRT

16. Thermal Capacity
The heat capacity or thermal capacity of a substance
can be defined as the amount of heat required to
change its temperature by one degree for the whole of
the substance.
Heat energy is the measure of the total internal energy
of a system. This includes the total kinetic energy of
the system and the potential energy of the molecules.
Heat capacity for a given matter depends on its size or
quantity and hence it is an extensive property.
Q=CΔT
The unit of heat capacity is joule per Kelvin or joule
per degree Celsius.

17. Specific Heat Capacity
Specific heat capacity for any substance or matter is defined as the amount
of heat energy required to raise the temperature of a unit mass of that
substance by one degree Celsius.
Mathematically it is given as:
Q= m c ΔT
The SI unit for specific heat capacity is joule per kelvin per kilogram
J/kg/K or JK−1kg−1
Basically it is used to select the materials which are having the fastest heat
absorbing ability

18. Change of State of Matter
Changing states of matter occur when matter loses or absorbs energy.
When a substance absorbs energy; the atoms and molecules move more rapidly
and this increased kinetic energy pushes particles far enough that they change
form.
This energy is usually heat or thermal energy.
A change of state is a physical change in a matter.
They are reversible changes and do not involve any
changes in the chemical makeup of the matter.
Common changes of the state include melting,
freezing, sublimation, deposition, condensation,
and vaporization.

19. Latent Heat
Latent heat is energy transferred in a process without change of the body's
temperature
Types of Latent Heat Transfer
 Solid-to-Liquid: Latent Heat of Fusion
 Liquid-to-Gas: Latent Heat of Vaporization

20. Formula for Latent Heat
The formula for calculating the latent heat is given:
L = Q/M
where,
L - is Latent Heat
Q - is Amount of Heat Released or Absorbed
M - is Mass of Substance
Unit of Latent Heat
Latent heat is nothing but the heat required per kg to change the phase of any
substance.
Its unit is J⁄Kg or JKg-1

21. Latent Heat of Fusion
The latent heat of fusion is the heat consumed or discharged when matter melts,
changing state from solid to fluid at a constant temperature.
This implies that energy must be provided to the solid so as to dissolve it.
The latent heat of vaporization is the heat consumed or discharged when matter
evaporates, changing state from liquid to gas at a constant temperature.
Latent Heat of Vaporisation
Specific Latent Heat
The specific latent heat is the amount of energy required to change the state of 1 kg
of the substance without changing the temperature of the substance.
Latent Heat Fusion of Ice - The amount of heat needed to convert a unit mass of ice from its solid
state to its liquid form is known as the latent heat of the fusion of ice. Its Value is 33600 J/Kg
Latent heat of vaporization of water -The amount of heat energy required to change unit mass of
water into vapor at its boiling point under the atmospheric pressure without any change in the
temperature. Its Value is 2260000 J/kg

22. Conduction is the transmission of energy by the
movement of particles in touch with one another.
Characteristics of Conduction:
 There is no real migration of medium particles from
one location to another in this sort of heat transmission.
 A material contact between the two bodies is required for conduction.
 The heat transfer in conduction is slow.
 The heat transfer occurs through a heated solid object and it mostly occurs in
solids.
 The heat transfer takes place due to the difference in temperature.
Properties of Conduction

23. Properties of Convection
 Convection is the process of heat transfer in
fluids by the actual motion of matter.
 It happens in liquids and gases.
 It may be natural or forced.
 It involves a bulk transfer of portions of the fluid.
 Heat transfer occurs predominantly within these boundary layers.
 Heat convection relies on temperature differences between the
surface and the fluid.
 Smoother surfaces generally promote better heat transfer
compared to rough surfaces.

24. Properties of Radiation
 Radiation is a process in which heat energy travels in the form
of electromagnetic waves.
 Unlike conduction and convection, which rely on a medium
(solid, liquid, or gas), radiation can occur through a vacuum.
 Heat radiation travels at the speed of light, which is
approximately 3 × 10^8 m/s in a vacuum.
 All objects with a temperature greater than absolute zero emit
thermal radiation.
 The wavelength of thermal radiation depends on the
temperature of the emitting body. Higher temperatures result
in shorter wavelengths.
 The rate of heat radiation is proportional to the fourth power
of the absolute temperature of the emitting surface

25. Thank you