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## Heat and Thermal Energy

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### Heat and Thermal Energy Molecules in the mosh pit * 4 Thermodynamics- how heat moves Conduction- the transfer of heat by the direct contact of particles of ... – PowerPoint PPT presentation

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Title: Heat and Thermal Energy

1
Heat and Thermal Energy
• Molecules in the mosh pit

10/10/2013
4
2
Todays Warmup
• Today, something a little different.
• Here are some totally cool sidewalk chalk
drawings (anamorphic illusions) by British artist
Julian Beever.

3
Todays Warmup
4
Todays Warmup
5
Todays Warmup
6
Todays Warmup
7
Todays Warmup
8
Todays Warmup
9
Todays Warmup
10
Todays Warmup
11
Todays Warmup
12
Todays Warmup
• Hip-hop Science

13
Todays Objectives
• Intro to heat and thermal energy
• heat vs temperature
• Measurement of heat
• Definition of specific heat
• Thermal energy BrainPop
• CPS quiz next class period!
• energy and heat

14
Thermal Energy
Notes
Questions Vocabulary words Formulas Main
Ideas Possible Test Questions Key Words
Notes
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Summary of the notes and information learned
15
What is temperature
• Temperature is a measurement used to quantify the
sensations of hot or cold, but what does
temperature actually measure?
• Molecules are constantly moving- they have
kinetic energy. Some are moving quickly, some
slowly, up, down, sideways They bounce off each
other like dancers in the mosh pit.
• What happens when you heat molecules?

16
What is temperature
• Heated molecules have more energy. They speed up
and bounce around more. If we heat a cup of water
all of the molecules increase their speed and
random motion.
• The temperature of an object measures the average
kinetic energy of its molecules.

17
Thermal Energy (aka Heat)
• The thermal energy of an object or substance is
the TOTAL (SUM) energy (potential and kinetic) of
its molecules
• Mass, properties of the substance and temperature
are involved here
• For example- one cup of boiling water has less
thermal energy (heat) than one gallon of boiling
water- even though both are at the same
temperature 100 degrees C (212 degrees F).

18
Kinetic Theory
• Kinetic Theory helps explain heat energy and heat
transfer.
• It says all matter is made of constantly moving
particles.
• Lets see that in action!

19
Kinetic Theory
• Lab Activity
• Work in groups of 4 One paper/graph per two
students
• Materials
• Stopwatch
• 250 ml glass beaker
• 100 ml ice
• Thermometer
• Hot plate
• Take temperature measurements every 30 seconds
until Mr. Rasure says to stop
• Graph results

20
Kinetic Theory
21
Temperature Scales
• The English system uses Fahrenheit to measure
temperature.
• In this scale water freezes at 32 degrees and
water boils at 212 degrees.
• Room temp is about 68 degrees.

22
Temperature Scales
• Most of the world (and all scientists) use the
Celsius scale- measured in degrees centigrade
• Water freezes at 0 degrees Celsius and boils at
100 degrees.
• Room temperature would be about 25 degrees.

23
Temperature Scales
• To convert between the two use these formulas
• F 1.8C 32
• C (F 32) / 1.8

24
Temperature Scales
• The Kelvin scale and absolute zero
• This temperature scale is named after the British
mathematician and physicist William Thomson
Kelvin, who proposed it in 1848.
• Absolute zero is the lowest possible temperature
where nothing could be colder, and no heat energy
remains in a substance. Absolute zero is the
point at which molecules do not move!

Kelvin Celsius Fahrenheit
Water boils 373.16K 100C 212F
Water freezes 273.16K 0C 32F
Absolute zero 0K -273.16C -459.7F
25
Conversion Practice
• 1. Body Temperature 98.6 F (Convert to C)
• 1. C (F - 32) X 5/9 C (98.6 - 32) X 5/9
66.6 X 5/9 37C
• 2. Boiling Temp of Water 212 F (Convert to C)
• 2. C (F - 32) X 5/9 C (212 - 32) X 5/9
180 X 5/9 100 C
• 3. Moderate Oven 175 C (Convert to F)
• 3. F (C X 9/5) 32 F (175 X 9/5) 32
315 32 347 F
• 4. Hot Summer Day 38 C (Convert to F)
• 4. F (C X 9/5) 32 F (38 X 9/5) 32
68.4 32 100.4 F

26
How does a thermometer work?
• Thermometers work through thermal expansion.
• As molecules are heated the gain kinetic energy
and the volume of a substance increases
• The liquid in a thermometer (colored alcohol or
mercury) expands and rises in the glass tube as
it gets warmer.
• Digital thermometers work because of electrical
resistance. The warmer a wire the more resistance
it has to the flow of electrons.

27
Specific Heat
• Different substances require different amounts of
heat to rise to the same temperature- a wood
handled pot of boiling water is much cooler to
the touch than a steel handled pot of boiling
water.
• Why?
• Conductors and Insulators

28
Specific Heat
• Specific heat is a property of a substance that
tells how much the temperature goes up when a
given amount of heat is applied.
• Specific Heat amount of energy needed to raise
the temperature of 1 g of material 1 C
• A large/high specific heat means you have to put
in a lot of energy for each degree increase in
temperature.

29
Specific Heat
• Water has a high specific heat
• Water can absorb more heat/energy before its
temperature rises

30
Specific Heat Formulaas shown on TAKS chart
.
8368 J/g C
Lets Practice for candy!
31
Specific Heat
Ex Calculate the amount of heat required to
raise the temperature of 78.2g of water from 10?C
to 35?C. Specific heat of water 4.18
J/(g?C) Heat 4.18 J/(g?C) (78.2g)(35?C -
10?C) 8171.9 J
32
Specific Heat
Ex Calculate the amount of heat required to
raise the temperature of 78.2g of water from 10?C
to 35?C. Specific heat of water 4.18
J/(g?C) Heat 4.18 J/(g?C) (78.2g)(35?C -
10?C) 8171.9 J
33
Thermodynamics- how heat moves
• Thermal energy always travels from higher
temperatures to lower temperatures
• Thermal energy (heat) can be transferred in three
ways
• Conduction
• Convection

34
Thermodynamics- how heat moves
• Conduction- the transfer of heat by the direct
contact of particles of matter

35
Thermodynamics- how heat moves
• Heat continues to transfer until both objects
reach thermal equilibrium (same temperature)
• Materials that transfer heateasily are called
conductors.Those that transfer thermalenergy
poorly are calledinsulators.

36
Thermodynamics- how heat moves
• Why would a Styrofoam cup not transfer the heat
of hot coffee to your hand as quickly as a metal
cup???

37
Thermodynamics- how heat moves
• Convection- the transfer of heat by the actual
motion of a fluid (liquid or gas) in the form of
currents.

38
Thermodynamics- how heat moves
• Radiation- the transfer of heat by
electromagnetic waves.
• Does not require matter to travel through (and
thus can travel through the vacuum of space)
• Transfers heat in all directions
• Requires no contact
• Can go through transparent materials

39
Thermodynamics- how heat moves
• Electromagnetic waves can be
• Infrared
• Visible light
• Ultraviolet
• The heat we enjoy from the sun comes to us as

40
Thermal Energy
Notes
Questions Vocabulary words Formulas Main
Ideas Possible Test Questions Key Words
Notes
Notes
Notes
Notes
Notes
Notes
Notes
Notes
Notes
Summary of the notes and information learned
41
Todays Assignment
• There are many types of heating and cooling
systems found in the world around us including
weather systems, living systems, and mechanical
systems. Chapter 29 (pg. 471) gives us an
overview of these systems.
• Lets use this chapter to answer the questions
shown on page 489 (Concept Review 1 through 10).
Write both the question and a complete answer.
Use a clean sheet of paper you can turn in when
complete.

42
CPS Quiz and Homework Sheet
• You may use your notes/lab-book, BUT you may not
• Subjects covered include
• Energy
• Heat
• Thermodynamics

43
Test Formulas
F 1.8C 32 C (F 32) / 1.8
Ohms Law I V/R (Iamps, Vvolts, Rohms of
resistance)
44
Make it a great day Mustangs!