This document summarizes key concepts about temperature, heat transfer, and clinical thermometers. It defines common temperature scales (Celsius, Fahrenheit, Kelvin) and concepts like thermal expansion, heat, internal energy, specific heat capacity, phase changes, and latent heat. It describes different methods of heat transfer (conduction, convection, radiation). It outlines direct and indirect types of clinical thermometers, including liquid-in-glass, chemical dot matrix, digital, thermocouple, infrared thermometers and their uses.

1. Chapter12: Temperature
and Heat

2. COMMON TEMPERATURE SCALES
Celsius to Fahrenheit
C l i t F h h it
T (F) = [1.8 x T (C)] + 32
Fahrenheit to Celcius
T (C) = T (F) – 32 / 1 8
1.8
Celsius to Kelvin
Kelvin,
Kelvin to Celsius
T (C) = T (K) – 273
T (K) = T (C) + 273

3. LINEAR THERMAL EXPANSION OF A SOLID
• The increase in any one dimension
of a solid iis called li
f lid ll d linear expansion.
i
• The change in length is directly
proportional to the change in
temperature : ∆L ≈ ∆T
• The length of an object changes
when its temperature changes:
p g
ΔL = α Lo ΔT
• Common Unit for the Coefficient of
Linear Expansion: 1
= (Co )
−1
Co

5. APPLICATIONS OF LINEAR THERMAL
EXPANSION OF SOLIDS

6. VOLUME THERMAL EXPANSION
• Th volume of an object changes
The l f bj t h
when its temperature changes:
ΔV = β Vo ΔT
coefficient of
volume expansion
• Common Unit for the Coefficient of Volume
Expansion: 1
()
o −1
=C
o
C

7. APPLICATIONS OF VOLUME
THERMAL EXPANSION

8. HEAT AND INTERNAL ENERGY
• Heat is energy that flows from a
higher- temperature object to a
lower- temperature object
p j
because of a difference in
temperatures.
• SI Unit of Heat: joule ( )
j (J)
• The heat that flows from hot to
cold originates in the internal
energy of the hot substance.

9. Heat and Temperature Change:
Specific Heat Capacity
•SSpecific H t C
ifi Heat Capacity: iis th h t th t must be supplied or
it the heat that tb li d
removed to change the temperature of a substance.
• The amount of heat needed to cause a temperature change
p g
depends on the mass of the object, size of the temperature
change, and the substance of which an object is made
Q = mc Δ T
• Common Unit for Specific Heat Capacity: J/(kg·Co)
p p y /( g

10. Example: A Hot Jogger
In a half-hour, a 65-kg jogger can generate 8.0x105J of heat. This
heat is removed from the body by a variety of means, including
the b d ’
th body’s own temperature-regulating mechanisms. If the heat
t t l ti hi th h t
were not removed, how much would the body temperature
increase?
Q = mcΔT
8.0 × 105 J
Q
ΔT = = = 3. 5 C o
[ )]
(
mc (65 kg ) 3500 J kg ⋅ Co

11. Sample problem
• How much heat is needed to increase
the temperature of 200 g of water
p
5.0°C? (cwater1.0 kcal/(kg.C°)
• How much heat is needed to increase
the temperature of 200 g of lead
5.0 C?
5.0°C? (c lead = 0.030cal/g °C)
C)

12. Heat Units other than Joule
• Kilocalorie
– The amount of heat needed to raise the temperature of 1kg of
water by one Celcius degree
Q = mcΔT
– c = 1.0 kcal/(kg.C°)
• B iti h Thermal Unit (Btu)
British Th l U it (Bt )
– Amount of heat needed to raise the temperature of one pound
of water by one Fahrenheit degree.
• Joule
– There is a relationship between energy in work and energy in
heat.
– 1kcal = 4186 joules or 1 cal = 4.186 joules
– Also known as mechanical equivalent of heat

13. HEAT AND PHASE CHANGE : LATENT HEAT
• Phase changes require large
amounts of energy compared
to the energy needed for
temperature changes.
• Energy used to cause a phase
change does not cause a
temperature change
change.
• The amount of energy g
required is proportional to the
number of molecules in the
object and to the forces
acting b t
ti between molecules.
l l

14. CONCEPTUAL EXAMPLE
• Suppose you are cooking spaghetti and the instructions say “boil
p
pasta in water for 10 minutes.” To cook spaghetti in an open pot with
pg p p
the least amount of energy, should you turn up the burner to its
fullest so the water vigorously boils, or should you turn down the
burner so the water barely boils?

15. LATENT HEAT
• Latent Heat: is the heat supplied or removed in changing the
pp gg
phase of a mass (m) of a substance
Q = mL
• SI Units of Latent Heat: J/kg
• Latent heat of fusion (Lf): change between solid and liquid
phases
• Latent heat of vaporization (Lv) change between li id and
t th t f i ti ( ): h bt liquid d
gas phases
• Latent heat o sub a o ( s): change between solid a d gas
ae ea of sublimation (L c a ge be ee so d and
phases

17. Chapter 13
The Transfer of Heat

18. CONVECTION
Convection is the process
in which heat is carried
from one place to
another by the bulk
movement of a fluid.

19. CONDUCTION
• Conduction is the process
whereby h t is transferred
h b heat i t f d
directly through a material, with
any bulk motion of the material
playing no role in the transfer.
• Movement of heat by atomic
collisions; transfer of heat
through stationary matter by
physical contact
hil tt
• Materials that conduct heat well
are called thermal conductors,
and those that conduct heat
poorly are called thermal
insulators.

20. The amount of heat Q that is conducted through the bar
depends on a number of factors:
1. The time during which conduction takes place.
2. The temperature difference between the ends of the bar.
3.
3 The
Th cross sectional area of the bar.
ti l f th b
4. The length of the bar.

21. RADIATION
• R di ti
Radiation i th process iin which
is the hi h
energy is transferred by means of
electromagnetic waves.
• A material that is a good absorber
is also a good emitter
emitter.
• A material that absorbs completely
p y
is called a perfect blackbody.

23. DIAGNOSTIC AND THERAPEUTIC
USES OF HEAT
• Thermography: indication of blood supply
g py pp y
– Decreased: deficiency in blood flow to a specific region
(clotting, stroke)
– Increased: malignant tumor
g
• Heat pads: relaxation of muscles and increased blood flow
• Infrared radiation: premature or newborn babies
• Microwave or radio diathermy (controlled to affect only
intended area)
• Ultrasound diathermy (energy carried by the sound can be
converted as thermal energy)
• Therapeutic Uses of Cold: lowered temperatures as local
anesthetic
– Ice packs
– Cryosurgery (treatment of warts, tumors, Parkinson’s)
g ( )

24. CLINICAL APPLICATION: THERMOMETERS
• A thermometer is used in health care to measure and monitor body
temperature.
temperature
• It allows a caregiver to record a baseline temperature when a
patient is admitted
admitted.
• Repeated measurements of temperature are useful to detect
deviations from normal levels and also useful in monitoring the
effectiveness of current medications or other treatments.
• Thermometers are usually made of a thin glass tube containing a
liquid.
• The temperature is measured by observing how far up the tube the
liquid rises. Different liquids have different nonlinear expansions.

25. TYPES OF CLINICAL THERMOMETERS -
DIRECT
• EXPANSION : Liquid-in-glass
q g
LIQUID
thermometers are devices
consisting of a bulb attached to Clear
glass chamber filled with liquid; glass
columns are marked with a
measurement scale.
• PRINCIPLE: Liquid-in-glass Lens
front
thermometers rely on the
principle that a liquid changes
its volume relative to its
temperature. White
backing
Capillary

26. TYPES OF LIQUID EXPANSION THERMOMETERS
Q
• Mercury in-glass: a thermometer consisting of
mercury in a glass tube.
• Calibrated marks on the tube allow the
temperature to be read by the length of the
mercury within the tube, which varies according
to the temperature.
• ADVANTAGES
– Mercury has large and uniform expansion
abilities, its silvery appearance allows for easy
reading, & stability.
• DISADVANTAGES
– When liquid mercury is spilled, it forms droplets
that accumulate in the tiniest of spaces and
emit vapors into the air. It is odorless, colorless,
and very t i
d toxic.
– Occur by breathing vapors, by direct skin
contact or by eating food or drinking water
contaminated with mercury
mercury.

27. TYPES OF LIQUID EXPANSION THERMOMETERS
Q
• ALCOHOL-IN-GLASS: Similar to mercury-in-
glass thermometer but contains colored
alcohol.
• ADVANTAGE: less toxic than a mercurial
thermometer
• DISADVANTAGES: Alcohol has a smaller
density of 0.79 g/cm3 [compared to the
density
densit of mercury = 13.6 g/cm3] With
merc r 13 6 ].
alcohol, there is greater increase in
volume, requiring either a longer stem or a
wider capillary tube.

28. TYPES OF CLINICAL THERMOMETERS
• CHEMICAL - DOT MATRIX OR PHASE CHANGE: Plastic strips
or adhesive patches that indicate a temperature
in response to the thermal change in chemical
dots.
• These devices vary in usefulness depending on
y p g
their resolution.
• DOT MATRIX: Each dot contains a different
combination of a chemical mixture that will melt
and change color from beige to bright blue at a
specific temperature.
• Temperature readings are indicated by the
T t di i di t d b th
number on the thermometer that corresponds
with the last blue dot.
• The device registers a temperature within 60
seconds and can be read after waiting an
additional 10 seconds for a stable measurement;
the last dot to turn blue constitutes the body
temperature.

29. TYPES OF CLINICAL THERMOMETERS -
DIRECT
• LIQUID CRYSTAL DISPLAY: A
chemical thermometer made by
impregnating spots of liquid
crystal material onto a spatula
spatula.
• If mixed with suitable dyes the
y
transition from solid to liquid phase
is demonstrated by the color of
the spot.
• Liquid crystal paints are also
available which can be used to
demonstrate temperature
distribution by color over parts of
the body.

30. TYPES OF CLINICAL THERMOMETERS -
INDIRECT
• THERMOCOUPLE: A thermocouple consists of
two junctions at two different metals. If
the two junctions are at different Thermocouple
temperatures, a voltage is p
p g produced
that depends on the temperature
difference
• DIGITAL : Electronic digital thermometers
are well-known and widely used. They
have several advantages including fast
response time, ease of reading and the
lack of mercury or other potentially
harmful liquids
q
• PACIFIER
• ORAL, RECTAL, AXILLARY
http://www.digitalthermometers.net

31. TYPES OF CLINICAL THERMOMETERS -
INDIRECT
• INFRARED: Infrared thermometers
measure temperature using
electromagnetic radiation such as
infrared emitted f
if d itt d from object. By
bj t B
knowing the amount of infrared
energy emitted by the object and its
emissivity
• Tympanic
• Temporal Tympanic
http://www.digitalthermometers.net