RECALL
OBJECTIVES
1. Differentiate heat from
temperature.
2. Infer the conditions necessary
for heat transfer to occur.
3. Explain the three modes of heat
transfer: conduction, convection,
and radiation.
What is temperature?
Temperature is a measure of the degree
of hotness or coldness of an object. It
can be described by the units Celsius,
Fahrenheit, Kelvin, and Rankin.
Thermometer is the instrument used to
measure temperature.
What is heat?
Heat can be defined as the thermal
energy that is being transferred from
one object to another because of
temperature difference.
“Heat always flows from hotter objects to
objects with lower temperature”.
Heat Vs. Temperature
Heat is the
actual
energy…
Temperature is
the measure of
average kinetic
energy of
particles in a
substance.
Heat is NOT Temperature
Mechanism of Heat
Transfer
 Heat is measure of the internal energy
that has been absorbed or transferred
from one body to another.
Heating is the process of increasing internal
energy.
Cooling is the process of decreasing internal
energy.
Two general ways wherein heating can
occur:
1. From a temperature difference, with
energy moving from the region of
higher temperature to a region of
lower temperature.
2. From an object gaining energy by
way of energy from conversion.
Heat Transfer
Methods
Heat transfers in three ways:
Conduction
Convection
Radiation
CONDUCTION
is the flowing of heat energy from a hightemperature object to a lower-temperature
object.
It is the transfer of energy from molecule to
molecule.
CONDUCTION
When you heat a metal strip at one end, the
heat travels to the other end.
As you heat the metal, the particles vibrate,
these vibrations make the adjacent particles
vibrate, and so on and so on, the vibrations are
passed along the metal and so is the heat.
When the metal is heated, this ‘sea of
electrons’ gain kinetic energy and transfer it
throughout the metal.
The outer
electrons of metal
atoms drift, and
are free to move.
Insulators, such as wood and plastic, do
not have this ‘sea of electrons’ which is
why they do not conduct heat like metals.
Why does metal feel colder than
wood, if they are both at the same
temperature?
CONVECTION
is the primary way that heat moves through
gases and liquids.
Convection is the movement of liquids or
gases from a colder region to a warmer
region producing a current.
CONVECTION
takes place when heated molecules move
from one place to another, taking the heat
with them. Convection is common in both
the atmosphere, as well as in the oceans.
Convection
What happens to the particles in a liquid
or a gas when you heat them?
The particles spread out and
become less dense.
Cold air sinks
Where is the
freezer
compartment
put in a fridge?
Freezer
compartment
It is put at
the top,
because cool
air sinks, so it
cools the food
on the way
down.
It is warmer
at the
bottom, so
this warmer
air rises and
a convection
current is set
up.
RADIATION
Involves the form of energy called radiant
energy- energy that moves through space.
It is in the form of invisible waves.
RADIATION
Radiant energy- is any energy including
heat that is transmitted by radiation.
Infrared waves or Radiant heat- the part of
the EM wave that makes us feel warm.
The transfer of energy by electromagnetic
waves
Examples: Sun, fire, and light bulb
RADIATION
Why are houses painted white in
hot countries?
White reflects heat radiation and keeps the
house cooler.
OBJECTIVES
1. Describe the different types
of charging processes.
2. Explain the importance of
earthing or grounding.
“ELECTRIC”
Electric from the Greek word electron,
meaning “like amber”.
Thales of Miletus- He discovered the
attraction between amber and wool during
600 BC
Electrical energy or
electricity
is a form of energy that comes from
electrically charged bodies such as ions and
electrons. The movement of electrons
(negatively charged) causes the formation
of electricity.
LAW OF CHARGES
Neutrons is the electrically neutral
particles.
Protons carry a positive charge and
electrons carry a negative charge.
Electrification or
charging by contact
is the process of rubbing two materials
together and then separating them to
produce the effect.
Charging Processes
Charging is a process by which an
insulator or an insulated conductor receives
a net charge.
Conductors are materials that permit
electric charge to move from one region to
another.
Insulators are materials that do not permit
the passage of charges through them.
Two charging Processes
1. Charging by conduction requires
contact between the neutral body and the
charged object.
2. Charging by induction
does not require contact but does require
the presence of a ground.
Earthing or grounding
is used in various
appliances for
safety and to
reduce the amount
of fires when there
is lightning.
Recitation
quiz
Mechanics
 Identify the method of heat
transfer taking place
 Chat your answer on the chat box
using private message
 You only have 30 sec per question
 Write the number of the item
before your answer
Methods of Heat Transfer
Conduction- transfers heat from
higher temperature objects to
lower temperature objects.
-molecule to molecule
- Usually occur in solid
Methods of Heat Transfer
Convection- transfers heat from
warmer region to colder region.
-molecules move from one place to
another producing current
- Usually occur in gasses and liquids
Methods of Heat Transfer
Radiation- transfers heat even
without direct contact
-molecules move in space
Identify the method of heat transfer taking place
(conduction, convection, radiation)
1. Hot coffee is stirred with a
spoon, the spoon gets hot due to
CONDUCTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
2. A chair is placed several feet from a fire
in a fireplace. The fireplace has a glass
screen. The side of the chair facing the
fireplace gets warm because of
RADIATION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
3. A certain type of decorative lamp
contains colored liquids. These liquids
form globs that break off and rise to the
top of the liquid. The globs rise due to
CONVECTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
4. Near the ceiling of a room the air
is warmer. The warm air rises
because of
CONVECTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
5. A college student holds the back
of his hand near an iron to see if it
is hot. Heat is transferred
to his hand by_____.
RADIATION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
6. A heater is placed under one
corner of a water bed mattress.
Warm water moves throughout
the mattress because of ______
CONDUCTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
7. A certain type of stainless steel
cookware has a layer of copper applied to
the bottom to help it
heat evenly. The copper transfers heat to
the pan by __________
CONDUCTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
8. In a swimming pool, the water
near the surface is slightly
warmer. The warm water rises
because of _________
CONVECTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
9. One end of a copper rod is placed in a
flame of a Bunsen burner. Small pieces of
wax placed along the rod melt
progressively at larger distance from the
flame. Heat is transferred through the rod
by ________
CONDUCTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
10. A house burns down. On the house
across the street, all of the vinyl siding is
twisted and wraped by the heat. The heat
was transferred across the street by
________.
RADIATION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
11. Warm air over the beach rises while
cooler dense air from the ocean rushes in
due to _________
CONVECTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
12. A fireman feels a door and it is hot
from the fire on the other side of the
door due to ________.
CONDUCTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
13. A huge rock at the state park
gets so hot during the day that you
can’t sit on it. The rock gets hot
due to_____
RADIATION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
14. You lay on that same rock
(no.13) at night so that you can
keep warm by __________.
CONDUCTION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
15. The metal skewer you are holding
near the fire gets so hot that you drop
your marshmallow in the campfire.
The metal skewer and your hand get
hot because of ________.
CONDUCTION
RADIATION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
16. The cause of weather systems
on earth is _______________.
CONVECTION
RADIATION
Identify the method of heat transfer taking place
(conduction, convection, radiation)
17. You are in the top bunk of a bunk bed
and you want to turn the air conditioner
on because you feel hot while your friend
on the bottom bunk is fine is caused by
_______.
CONVECTION
RADIATION
THAT’S ALL FOR TODAY! 