Chapter 16
Thermal Energy and Heat
Thermal Energy and Matter
 Heat: is the transfer of thermal
energy from one object to another
due to a difference in temperature
 Heat flows from:
HOT  COLD
 Cold: losing heat energy
 Hot: gaining heat energy
 Kinetic Theory- all matter is made of
particle (atoms, molecule, ions).
These particles are always in random
motion.
 Higher Temp = higher kinetic = faster
motion
 Temperature: is how hot or cold an
object is compared to some reference
point
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Examples:
Outside Temperatures
Temperature of buildings 70.0’F
Runoff Water Temp. 35-42’F
Body Temp. 98.6’ F
 Thermometer: tool used to measure
temp. 3 different scales ‘C ‘F K
 Mercury expands as the thermometer
gains heat (UP)
 Mercury contracts as the
thermometer loses heat (DOWN)
 Formulas pg 255 C  F, F C
 Thermal energy: depends on mass,
temperature and phase of an object.
 Thermal energy is caused by the
movement of atoms and molecules
(friction)
 Mass: greater mass = greater thermal e.
 More mass = longer to heat up & cool down
 Temp. greater temp = greater thermal e.
 Greater SpecificHeat = Greater thermal E
 Phase: depends on amount of thermal E.
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Solid:
Liquid:
Gas:
Plasma: most heat energy
The States of Matter, Molecular Stickiness, and Thermodynamicsitl.chem.ufl.edu
 Thermal Expansion: occurs because
particles of matter tend to move faster and
spread out as temperature increases
 INCREASE HEAT = INCREASE SIZE
 DECREASE HEAT = DECREASE SIZE
 Ex. Joints in side walks (celotex), joints in
bridges, thermostats in homes, Thermometer
 Balloon Demo: expanded as we added heat
 Specific Heat: a physical property that
describes how a substance absorbs heat
 Different substances absorb heat at
different rates
 The lower a material’s specific heat, the
more its temp. will increase as heat is
added. (heats & cools faster)
 Metals: low specific heat
 Nonmetals: high specific heat
 Specific Heat of Common Materials
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Water =
Plastic =
Air =
Iron =
Silver =
4.18
J/g-’C
1.8 to 2.1 J/g-’C
1.01
J/g-’C
.449
J/g-’C
.225
J/g-’C
Measuring Heat Changes
 Calorimeter: is an instrument used to
measure changes in a material’s heat
 Closed container that holds water,
thermometer, stirring rod
 Used to calculate specific heat
 Used to calculate # of calories in food
 Picture on next slide and in book
http://www.agro.cmu.ac.th/department/fe/equip
 http://www.agro.cmu.ac.th/departme
nt/fe/equip_file/031_1.jpg
http://www.agro.cmu.
ac.th/department/fe/e
quip_file/031_1.jpg
http://research.chem.psu.edu/mallouk/ilab/models.htm
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16.2 Heat & Thermodynamics
 There are 3 ways that thermal energy
is transferred from one object to
another
 Conduction
 Convection
 Radiation
 Conduction: is a heat transfer when 2
objects are touching (direct contact)
 There is NO transfer of matter
 Conduction works fastest with:
 Solids  Liquids  Gases
 The particles of liquids and gases are
farther apart than solids, therefore
heat is not transferred as quickly
 Thermal Conductors: are materials
that allow heat and electricity to pass
through them easily
 Metals
 Copper wire for electrical circuits, gold
wire in spaceships, pots & pans
 Low specific heat values
 Thermal insulators: are materials that
DO NOT allow heat and electricity to
pass through them easily
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Non-metals
Wood, plastic, air, glass, fiberglass
Protect items from heat and electricity
High specific heat values
 Convection: heat transfer that takes place
in fluids (liquids and gases)
 HOT AIR/WATER RISES
 Convection Currents: currents in liquids or
gases, these currents transfer thermal
energy (caused by difference in density)
 Ex. Pavement, beaker of hot water,
ocean currents, weather patterns, wind
 Radiation: is the transfer of thermal
energy (heat) by waves through
space
 Radiation happens through air and
empty space
 Ex. Sun, wood burning stove,
fireplace, candles
 All objects radiate thermal energy
 1st Law of Thermodynamics: states
that thermal energy is conserved
 Heat energy can’t be created nor
destroyed
 Heat energy can only be transferred
and converted
 2nd Law of Thermodynamics: states
that heat CAN flow from COLDER
objects to HOTTER objects, ONLY if
work is done.
 Ex. refrigerator, freezer, A.C.
 Freon: refrigerant liquid/gas that
is used in the cooling process
(cars)
ENTROPY:
 The measure of how dispersed the
energy is.
 3rd Law of Thermodynamics: states
that absolute zero CAN’T be reached
 Absolute Zero: is the coldest possible
temperature where molecular (atoms)
motion stops
 Absolute Zero = 0 K
Using Thermal Energy
 Heating Systems:
 Forced-air: fuel heats air and fan pushes
through the building. Cold air returns
 Radiator:hot water or steam heat
through radiation to the air. Uses a
boiler to heat water
 Electric: electricity heats coils in floor or
ceiling by conduction.