Transcript WHAT IS HEAT?

HEAT
AND
HEAT
TRANSFER
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
More Heat
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. The term
for this type of expansion is called THERMAL
EXPANSION.
Thermal expansion is why running a tight jar
lid under warm water loosens the lid.
*pg 154
THERMAL EXPANSION
The spreading of particles or
increased volume when an object is
heated is known as THERMAL
EXPANSION
WHAT IS HEAT?
Heat=transfer of
energy between objects
that are different
temperatures (atoms
rubbing together).
pg. 155
Another word for heat is
THERMAL ENERGY.
Hot objects contain more thermal energy than
cold objects
Heat Transfer= Heat (thermal energy) is
transferred from warmer objects to cooler
objects
.
How cold is cold?
There is no such thing as coldness. What
we call cold is really absence of heat or
slow atoms. Even when it is 15 degrees
outside, that is 15 degrees of HEAT,
NOT 15 degrees of COLD.
Can a balanced temperature ever be reached?
YES, IT’S CALLED THERMAL
EQUILIBRIUM
No energy transfer occurs
Pg. 156
THERMAL EQUILIBRIUM
The point at which two
objects reach the same
temperature.
HEAT IS TRANSFERRED IN
THREE WAYS
BY
CONDUCTION
CONVECTION
RADIATION
CONDUCTION
Transfer of heat from one substance to
another by direct contact.
Happens within and between objects that
touch each other
Best conduction happens in solids
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
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
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?
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
Convection currents cause the Earth’s tectonic plates to move about.
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.
Explain how each of these uses radiant heat.
BELLRINGER
1. Describe how heat is created.
2. Give 2 examples of thermal expansion.
3. What is the difference between hot and cold?
4. How does heat move?
5. Describe all the heat transfers in the diagram.
How does heat affect matter?
Physically: heat changes the state in which
matter exists i.e. melting, freezing,
evaporating, condensing
Chemically: for chemical reactions to occur,
chemical bonds must be broken and new
compounds formed. Requires energy to be
absorbed or released
HEAT ON EARTH
WATER AND LAND
Heat comes to the Earth from the
Sun by radiation.
Light passes through the atmosphere
Land and water absorb the light and become
warm
Land and water reflect infrared waves (also
radiant energy) back into space BUT NOT
ALL OF IT.
Water vapor, CO2 and other gases block
these waves and the Earth gets hotter.
Called the Greenhouse Effect
HEAT ON EARTH
HEAT ON EARTH
THE ATMOSPHERE
Because of the Earth’s curved shape, its surface
and atmosphere are NOT heated evenly.
If Earth was flat, all surfaces would be heated
evenly
Convection causes air to move between warm
regions and cold ones.
This redistributes the sun’s energy all over the
Earth.
Wind is caused from these convection patterns
HEAT ON EARTH
THE ATMOSPHERE
HEAT ON EARTH
THE ATMOSPHERE
HEAT ON EARTH
THE OCEAN
One interesting property
of water is that it can absorb
large amounts of heat.
Since most of Earth’s
surface is covered by water,
it is able to store much more
heat than land.
The climate of the entire
Earth is much more
moderate than it would be if
the oceans did not exist.
The oceans act like vast
heat storage tanks.
HEAT ON EARTH
THE WEATHER
The convection
patterns in the
atmosphere, the
heat stored in the
oceans and the
evaporation caused
by the sun’s rays
striking the Earth
all cause the
WEATHER.
HEAT ON EARTH
THE WEATHER
KATRINA APPROACHES
HEAT ON EARTH
UNDERGROUND
 Interior heat left over
from when the Earth
was formed 4.5 billion
years ago.
Convection currents
carry heat to the crust
but extremely slowly.
Rock is a poor
conductor.
Evidence of interior
heat: volcanoes,
geysers, bubbling hot
springs.
brass
aluminum
tines
steel
Hexagonal center
Stainless
steel
pits
copper
BELLRINGER
1. Describe how heat is created.
2. Give 2 examples of thermal expansion.
3. What is the difference between hot and cold?