1. Review

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11. Objectives
At the end of the period, you should be able to:
a. Define heat;
b. Describe the condition necessary for heat
transfer to take place and trace the direction in
which heat is transferred;
c. Differentiate Heat from temperature; and
d. Analyze changes in the temperature of water
inside the containers by performing the Activity
# 1 (warm me, Cool me Down).

12. What is Heat

13. Heat It Up!
What is heat?
• Heat is the energy
transferred from an
object at a higher
temperature to an
object at a lower
temperature.
• Energy in the form of
heat always flows
from hot to cold.
13

14. Draw an arrow in the direction in which energy in
the form of heat would flow.
Object 1 Direction of heat
flow
Object 2
Metal rod Fire
Ice cube Glass of warm
water
14
Previous
slide

15. Draw an arrow in the direction in
which energy in the form of heat
would flow.
Object 1 Direction of heat
flow
Object 2
Metal rod Fire
Ice cube Glass of warm
water

16. • Heat moves
from the
source to the
other object or
places.
• The water gets
hot because
heat from the
burning stove is
transferred to
it.

17. What is thermal energy?
• Thermal energy is the total kinetic energy of all
particles in a substance.
• Thermal energy is measured in joules (J).
17

18. How is heat related to thermal energy?
• Adding or removing heat from a substance will affect its
temperature and thermal energy.
• Heat, however, is not the same as thermal energy and
temperature.
• Thermal energy and temperature are properties of a
substance. Heat is the energy involved when these
properties change.
• Even though two materials might have the same
temperature, their thermal energies might be different.
• Thermal energy depends on how many particles are present
in the object.
Copyright © Houghton Mifflin Harcourt Publishing Company
18
Energy as heat will be transferred from the warmer object to the cooler object until
both objects are at the same temperature

19. What is the difference between thermal
energy and temperature?
• Temperature is related to the average kinetic
energy of particles.
• Thermal energy is the total kinetic energy of all
the particles.
• For example, a glass of water can have the same
temperature as a lake, but the lake has much
more thermal energy because the lake contains
many more water molecules.
Temperature and total amount of particles
determine the thermal energy of a substance.

20. Which has more thermal energy?
Bowl of Soup
Pot of Soup
20
Small balloon
Large balloon
Tiger
House cat

21. Let us Perform Activity #1
Materials Needed:
• 2 small containers (drinking cups or glasses)
• 2 big containers (enough to accommodate the
small containers)
• tap water
• hot water
• food coloring
• laboratory thermometers (with reading up to
100oC)

22. 22
Heat
is the transfer of
Thermal energy
by
Conduction Convection Radiation

23. HOW DOES HEAT TRANSFER?
HEAT ENERGY
•Energy transfer
Conduction
Convection
Radiation

24. 24
Energy as heat can be transferred in three main ways: conduction,
convection, and radiation.

25. Conduction
• One of the methods by which heat is
transferred.
• Takes place between objects that are in
contact with each other.
• In this way heat in an object travels from:
the HOT end the cold end

26. Example:

27. Heat Conductivities
Q1. Why we feel some objects colder or warmer than the
others?
- Because some objects conduct heat faster than the
other.
Ex.
-water(4.186 J)
-gold(.126J)
-aluminum(.900J)
Q2. Which usually feels warmer to our feet – the tiled
floor or the rug?
-rug

28. List of thermal conductivities of
common materials

29. Solids that conduct heat better are considered
good conductors of heat while those which
conduct heat poorly are generally called
insulators. Metals are mostly good
conductors of heat.
Ex. When we use a pot or pan to cook our food
over a stove, we usually use a pot holder made
of fabrics to grasp the metal handle.
In the process, we are using an insulator to
prevent our hand from being burned by the
conductor, which is the metal pan or pot.

30. What is convection?
• When water is boiled, the water moves
in roughly circular patterns because of
convection.
• This motion is due to density
differences that result from
temperature differences.
• The motion is called a convection
current.
30
• Convection is the transfer of energy as heat by the movement of a
liquid or gas.
• Convection occurs when a cooler, denser mass of gas or liquid
replaces a warmer, less dense mass of gas or liquid by pushing it
upward.

31. Convection
31

32. CONVECTION
Heated air
rises, cools,
then falls
Hot water
rises, cools,
and falls
Air near heater is
replaced by cooler
air, and
the cycle repeats

33. CONVECTION

34. SEA BREEZE AND
LAND BREEZE
SEA BREEZE LAND BREEZE

35. RADIATION
Sunlight is a form of
radiation that is radiated
through space to our planet
without the aid of fluids or
solids.
Since there are no fluids in
space, convection is not
responsible for transferring the
heat. Thus, radiation brings
heat to our planet.

36. What is radiation?
• Radiation is the transfer of energy by electromagnetic
waves.
• Examples of EM waves: visible light, microwaves, infrared
light
• When radiation is emitted from one object and then
absorbed by another, the result is the transfer of heat.
• Radiation can travel through empty space.
Unit 2 Lesson 3 Thermal Energy and Heat
36
p130

37. SUMMARY
• Heat is a thermal energy that is in transit.
• Heat transfer takes place between objects of
different temperature.
• When the object becomes warmer, it means that it
gained energy. When it becomes cooler, it means
that it lost energy.
• Heat energy always transfers from object of higher
temperature to object of lower temperature.
• Heat can be transferred in three ways: conduction,
convection, and radiation.

38. • Conduction takes place due to the vibrating and
colliding particles of objects that are in contact. It can
take place in solids, liquids, and gases but it takes place
best in solids.
• Conductivity refers to the ability of the material to
conduct heat. The higher the
conductivity of the object, the better it conducts heat.
• Metals are mostly good conductors of heat.
• Convection takes place in fluids because their particles
can move around. In
convection, the heat is transferred by the particles
themselves.

39. • During convection, warmer liquid or gas
expands and goes up while cooler liquid
or gas moves down.
• Heat transfer by radiation does not need
particles or a medium to take place.
• Different surfaces emit or absorb heat
differently. Dull and black surfaces absorb
heat better than bright and shiny surfaces.