Transcript Heat POWERPOINT - Bowling Green Independent Schools

What is Temperature?
What Do You Think?
What happens when you use a
thermometer to measure temperature?
© Fall 2005, Pflugerville ISD, 8th Grade
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
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
What is the difference between
temperature and heat?
Temperature is a
measure of the average
kinetic energy of
atoms.
Thermometers
are used to
measure
temperature
This means: the
higher the
temperature, the
faster the atoms
move the lower the
temperature, the
slower the atoms
move
Less Heat
© Fall 2005, Pflugerville ISD, 8th Grade
More Heat
What is Temperature?
Temperature is expressed by one of 3 scales:
© Fall 2005, Pflugerville ISD, 8th Grade
What is Temperature?
Thermal Expansion- As temperature rises,
volume (size) increases
© Fall 2005, Pflugerville ISD, 8th Grade
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
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
THERMAL EXPANSION
The spreading of particles (atoms)
or increased volume (size) when an
object is heated is known as
THERMAL EXPANSION
© Fall 2005, Pflugerville ISD, 8th Grade
THERMAL EXPANSION.
If energy is added to atoms, they move
faster. The faster they move, the further
apart they move. This spreading out of atoms
happens in solids, liquids and gases.
Thermal expansion is why running a tight jar
lid under warm water loosens the lid.
*pg 154
© Fall 2005, Pflugerville ISD, 8th Grade
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
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
Another word for heat is
THERMAL ENERGY.
Hot objects contain more thermal energy than
cold objects
.
© Fall 2005, Pflugerville ISD, 8th Grade
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
THERMAL EQUILIBRIUM
The point at which two
objects reach the same
temperature.
© Fall 2005, Pflugerville ISD, 8th Grade
What is Heat?
Reaching Thermal Equilibrium
© Fall 2005, Pflugerville ISD, 8th Grade
THERMAL EQUILIBRIUM
No energy transfer occurs
© Fall 2005, Pflugerville ISD, 8th Grade
What is Heat?
Energy is Transferred by 3 Methods:
© Fall 2005, Pflugerville ISD, 8th Grade
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
CONDUCTION
Transfer of heat from one substance to
another by direct contact.
Happens within and between objects that
touch each other
Examples: Sauce pan on a stove top, metal
spoon in a bowl of soup, ice melting in a
warm hand, hot shower, walking on hot coals
© Fall 2005, Pflugerville ISD, 8th Grade
Objects that heat up
easily are called
CONDUCTORS.
Metals are the best
conductors
Metal objects feel
cold because they
conduct heat AWAY
from your hand
© Fall 2005, Pflugerville ISD, 8th Grade
Objects that DO NOT
heat up easily are
called INSULATORS.
Things like glass,wood,
plastic and rubber are
good insulators
Which parts of the pan are conductors and which
are insulators?
© Fall 2005, Pflugerville ISD, 8th Grade
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
CONVECTION
 Transfer of heat in liquids and gases ONLY
 Heat moves up and down in a circular motion
called a CONVECTION CURRENT
 Heated liquids and gases are less dense &
rise carrying heat with them
 Examples: hang gliders, soaring birds, home
furnace heating & circulating air
© Fall 2005, Pflugerville ISD, 8th Grade
Convection currents cause the Earth’s tectonic plates to move about.
© Fall 2005, Pflugerville ISD, 8th Grade
What is Heat?
Radiation
© Fall 2005, Pflugerville ISD, 8th Grade
•Radiation is the
transfer of energy
through matter or space
through light energy,
such as visible light and
infrared waves
•Radiation is the only
type of energy transfer
where the objects don’t
have to touch
RADIATION
 transfer of heat through empty space in form of
infrared radiation waves (what we think of as heat
waves)
Examples: blacktop heats up on a sunny day, hot
sand on a beach, electric heaters.
© Fall 2005, Pflugerville ISD, 8th Grade
Explain how each of these uses radiant heat.
© Fall 2005, Pflugerville ISD, 8th Grade
Harcourt Science: States of Matter
BBC: Science
BrainPop: States of Matter
© Fall 2005, Pflugerville ISD, 8th Grade
Unit A : Chapter 1 : Section 1