Heat

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8th Grade Science
© Fall 2005, Pflugerville ISD, 8th Grade
Chapter 6- Heat
Section 1: What is Temperature?
Section 2: What is Heat?
Section 3: Matter & Heat
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Temperature?
What Do You Think?
What happens when you use a
thermometer to measure temperature?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Temperature Depends on Kinetic
Energy
•Kinetic Energy is the energy
of motion
•The faster the particles of
matter move, the more kinetic
energy they have
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Temperature?
Measuring Temperature
•Temperature is a
measure of the
Average Kinetic
Energy of a substance
•When you measure
temperature, you are
measuring the average
motion of the atoms
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Temperature?
Temperature is expressed by one of 3 scales:
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Temperature?
Thermal Expansion- As temperature rises,
volume increases
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Temperature?
Thermal Expansion
•When the metal rails
in this picture heated
up, they increased in
length and volume
•Thermal Expansion
caused the rails to
buckle and bend
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Temperature?
Thermal Expansion
•The asphalt in the
road expands when
heated and contracts
when cooled
•This results in cracks
and potholes due to
Thermal Expansion
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Heat?
What Do You Think?
Which is warmer, the tile or the rug on
a bathroom floor?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Heat?
Heat- A Transfer of Energy
•Heat is the transfer
of energy between
objects or particles
that are at different
temperatures
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Heat?
Heat- A Transfer of Energy
•Energy moves from
the warmer object to
the cooler object until
both are the same
temperature
•This is known as
Thermal Equilibrium
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Heat?
Reaching Thermal Equilibrium
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Heat?
Energy is Transferred by 3 Methods:
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Heat?
•Conduction is the
transfer of thermal
energy through
direct contact
•Hold a metal wire in
a flame and energy
travels from atom to
atom until it burns
your hand
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Heat?
Convection
•Convection is the
transfer of thermal energy
by the movement of a
liquid or a gas
•Convection is seen as
hot material rises and
cool material sinks
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
What is Heat?
Radiation
© Fall 2005, Pflugerville ISD, 8th Grade
•Radiation is the
transfer of energy
through matter or space
as EM waves, such as
visible light and infrared
waves
•Radiation is the only
type of energy transfer
where the objects don’t
have to touch
Unit A : Chapter 1 : Section 1
Matter & Heat
What Do You Think?
When you get overheated and start to
sweat, your body begins to cool off.
Why?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Matter & Heat
States of Matter
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Matter & Heat
Ice Crystal
•Particles of a solid
do not move fast
enough to pull apart,
so they vibrate in
place
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Matter & Heat
Melting of Ice
•Energy must be
transferred to a solid to
make it become liquid
•The water will remain
the same temperature
until all of the ice has
melted
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Matter & Heat
Evaporation of Water •Transfer more energy
to the water and its
particles move even
faster
•When the liquid water
molecules move fast
enough, they become
a gas
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Matter & Heat
Sweat Cools You Down
•When your body
gets too hot, you
perspire
•The liquid sweat
uses energy from
your body to
evaporate water
molecules
•You get cooler!
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Let’s Review!
-1-
What is temperature?
Explain what happens
when you use a
thermometer to measure
temperature…
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Let’s Review!
-2-
How is radiation different
from conduction and
convection?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Let’s Review!
-3-
When water evaporates,
the air near the water’s
surface becomes cooler.
Why?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Harcourt Science: States of Matter
BBC: Science
BrainPop: States of Matter
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
Pre-AP Extensions
• You should be able to explain Thermal
Conductivity and Specific Heat
Capacity.
• You should know what a Calorimeter is
and the difference between a calorie (cal)
and a Calorie (C)
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1
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