1. Module 3 Part 2
Temperature and Heat
Dr. Paul H. Comitz
pcomitz@live.com
2. Agenda
Temperature and Heat Transfer
Temperature
Heat Transfer and Heat Flow
Specific Heat
Thermal Expansion
Discussion:
Pascal's Principle
Lab : Temperature and Heat
http://phet.colorado.edu/en/simulation/balloons-
and-buoyancy
3. Course Modules
# Module Weeks Reading Quiz
1 Newton's laws 1 Ch 4,5 *
2 Conservation of Energy and
Momentum
2,3 Ch 6,7,8 Quiz 1
3 Thermodynamics 4,5 Ch 12,13,14
4 Electromagnetism 6,7 Ch 17,18 Quiz 2
5 Waves, Sound, and Light 8,9 Ch 16, 20, 21 Quiz 3
6 Modern Physics 10 Ch 23 Final Exam
* it is strongly recommended you read chapters 0 - 3
4. Module 3
Reading: Chapters 12,13,14
Chapter 12 – Matter
Chapter 13 - Fluids
Chapter 14 – Temperature and Heat Transfer
The Physics Classroom
http://www.physicsclassroom.com/class/thermalP
Exercise 3, due start of week 6 (4%)
Discussion 2– due tonight (5%)
Labs
Gas Properties (3.75%)
Temperature and Heat (3.75%)
5. Temperature
Temperature
a number that corresponds to the warmth or
coldness of an object
measured by a thermometer
is a per-particle property
no upper limit
definite limit on lower end
6. Temperature
Temperature is proportional to the average kinetic
energy per particle in a substance.
• gas—how fast the gas particles are bouncing to
and fro
• liquid—how fast particles slide and jiggle past one
another
• solid—how fast particles move as they vibrate and
jiggle in place
7. Temperature
Heat is a form of energy
Heat flows from hot to cold
Second law of Thermodynamics
Heat flows from an area of higher
temperature to an area of lower
temperature
There is no heat flow between areas of
equal temperature
Temperature refers to an exchange of
energy
8. There is twice as much molecular kinetic energy in 2 liters
of boiling water as in 1 liter of boiling water. Which will
be the same for both?
A. temperature
B. thermal energy
C. both A and B
D. neither A nor B
Temperature
CHECK YOUR UNDERSTANDING
9. There is twice as much molecular kinetic energy in 2 liters
of boiling water as in 1 liter of boiling water. Which will
be the same for both?
A. temperature
B. thermal energy
C. both A and B
D. neither A nor B
Explanation:
Average kinetic energy of molecules is the same,
which means temperature is the same for both.
Temperature
CHECK YOUR ANSWER
10. To say that body A has a higher temperature than body B is to say
that body A has more
A. thermal energy.
B. mass.
C. kinetic energy per particle.
D. potential energy.
Temperature
CHECK YOUR UNDERSTANDING
11. To say that body A has a higher temperature than body B is to say
that body A has more
A. thermal energy.
B. mass.
C. kinetic energy per particle.
D. potential energy.
Temperature
CHECK YOUR ANSWER
12. Temperature Scales
Celsius scale named after Anders Celsius (1701
–1744)
zero C for freezing point of water to 100C for boiling
point of water
Fahrenheit scale named after G. D. Fahrenheit
(1686–1736)
32F for freezing point of water to 212F for boiling point
of water
Kelvin scale named after Lord Kelvin (1824–1907)
0 K for freezing point of water to 373 K for boiling
point of water
zero at absolute zero, same size degrees as Celsius scale
Kelvins, rather than degrees are used
14. Heat
A form of internal kinetic and potential energy
Measured in
joules
1 joule = 1 kg m2/s2
calorie
1 calorie = 4.19J
kilocalorie
1 kilocalorie 4190 J
BTU
1 BTU = 1055 J
15. Heat
1 kilocalorie is defined as the
amount of heat necessary to raise
1kg of water by 1 degree C
1 BTU is the amount of heat
necessary to raise 1 lb. of water , 1
degree C
1 calorie is the amount of heat
necessary to raise 1g of water by 1
degree C
1 food calorie – 1 kilocalorie
16. Heat Transfer
Second Law of Thermodynamics
Heat flows from hot to cold
Hot Cold
Forms of heat transfers
Conduction
Convection
Radiation
17. Heat Transfer by Conduction
Heat transfer from warm to cold due to
molecular collisions
Conductors
Copper
Aluminum
Steel
Insulators
Glass
Asbestos
Wood
Styrofoam
18. Heat Transfer by Convection
Transfer of heat by the
movement of warm molecules
from one region of a gas or
liquid to another
Convective Weather
Sun heats earths surface
Cooler air is warmed and rises
Causes wind, clouds, rain
19. Heat Transfer by Radiation
Heat transfer through energy
transmitted in the form of rays and
waves
All life on earth depends on
transfer of energy from the sun
Radiated heat is a form of an
electromagnetic wave
20. Heat Flow and Thermal Conductivity
Similar to flow of electricity
Formula
Q = Kat(T2 – T1) /L
Q = heat transferred in J or BTU
K = thermal conductivity
A = Area
L = Thickness
T2 = temperature of hot side
T1 = temperature of cold side
22. Specific Heat
Measure of capacity to absorb
or give off heat
Definition:
the quantity of heat required
to change the temperature of
1 kg of a substance by 1
degree Celsius
Thermal inertia—resistance
of a substance to a change
in temperature
23. Specific Heat Capacity
The high specific heat capacity of water
has higher capacity for storing energy than almost any
other substance
24. Specific Heat Affects Climate
Specific heat affects climate
for Europeans, the Atlantic Ocean current carries
warm water northeast from the Caribbean regions and
retains much of its internal energy long enough to
reach the North Atlantic Ocean. Energy released is
carried by westerly winds over the European
continent.
25. Which has the higher specific heat capacity, water or land?
A. Water.
B. Land.
C. both of the above are the same
D. neither of the above
Specific Heat Capacity
CHECK YOUR UNDERSTANDING
26. Which has the higher specific heat capacity, water or land?
A. Water.
B. Land.
C. both of the above are the same
D. neither of the above
Explanation:
A substance with small temperature changes for large heat
changes has a high specific heat capacity. Water takes much
longer to heat up in the sunshine than does land. This difference
is a major influence on climate.
Specific Heat Capacity
CHECK YOUR ANSWER
27. Thermal Expansion
Thermal expansion
due to rise in temperature of a substance, molecules
jiggle faster and move farther apart
most substances expand when heated and contract
when cooled
railroad tracks laid on winter days expand and buckle
in hot summer
warming metal lids on glass jars under hot water
loosens the lid by more expansion of the lid than the
jar
28. Thermal Expansion
Thermal expansion (continued)
plays a role in construction and devices
example:
• use of reinforcing steel with the same rate of
expansion as concrete—expansion joints on bridges
• gaps on concrete roadways and sidewalks allow for
concrete expansion in the summer and contraction in
the winter
29. When stringing telephone lines between poles in the summer, it is
advisable to allow the lines to
A. sag.
B. be taut.
C. be close to the ground.
D. allow ample space for birds.
Thermal Expansion
CHECK YOUR UNDERSTANDING
30. When stringing telephone lines between poles in the summer, it is
advisable to allow the lines to
A. sag.
B. be taut.
C. be close to the ground.
D. allow ample space for birds.
Explanation:
Telephone lines are longer in a warmer summer and shorter in a cold winter.
Hence, they sag more on hot summer days than in winter. If the lines are not
strung with enough sag in summer, they might contract too much and snap during
the winter—especially when carrying ice.
Thermal Expansion
CHECK YOUR ANSWER
31. Change of Phase
Change in a substance from one form to
another
Fusion - Solid to Liquid
Freezing – Liquid to Solid
Vaporization – liquid to gas
Condensation – gas to liquid
Triple Point – the temperature and pressure
at which the solid, liquid, and gas phases
exist simultaneously
32. In Class Discussion
Pascal’s Principle (text 13.2)
Pascal’s principle states that a change in pressure in one part of a fluid is
transmitted to every other part; this is also the principle behind hydraulics.
Hydraulic devices can be used to multiply an applied force with the trade-off of
having to apply the force over a greater distance. Hydraulic devices are
commonly found in many areas of everyday life.
In this discussion, you need to:
Research and identify a device that uses hydraulics to operate. Use the ITT Tech
Virtual Library and other resources for your research.
In your own words, describe the device and the method to apply Pascal’s principle to it.
Use two examples to illustrate your explanation.
Include references to all sources you used in your research and posting.
Requirements:
Provide a complete, well-thought-out response.
Approx. 1 page (200 to 250 words)
Bring your completed work to next class
Be prepared to briefly present your response to the class