Lesson taken from the book Science 7 of Phoenix Pub. House by Lilia G. Venco et.al, 2012.

1. Heat and
Temperature
Prepared by:
Victor R. Oribe

2. What is heat?
Up to the middle of 19th century, it was
thought that heat was an
invisible, weightless substance called
Caloric Fluid.
When wood, for instance is burned, it is hot because it
produces large quantities of caloric fluid which is
transferred to other substance close by.
The burned wood, having lost its caloric fluid, is said
to have cooled off.

3. The theory of Caloric Fluid
was disproved around 1800
by Count Benjamin
Thompson Rumford, an
American-born physicist.
Count Benjamin Thompson
Rumford concluded that
heat was produced from
friction alone.

4. It was only about 40 years later that an English
physicist, James Prescott Joule proved that a
measurable amount of mechanical energy could
always be transformed into definite amounts of heat.
He concluded that heat
must be just another
form of energy.

5. Sources of Heat
Natural Sources
1. The Sun
When the sun’s energy reaches the earth, 30% of its is
immediately reflected back out into space.
Only 70% remains to
interact with the
earth, and warm it up.
Of the 70%, 20% is
energy to heat both the
surface of the earth, as
well as the ocean.

6. It is the sun’s heat
energy that makes
plants and animals to
provide themselves
with energy.
These plants provide
food for animals.
Human eat plants
and animals to
provide themselves
with energy.
Much of the heat on earth may be traced back to the
sun.

7. 2. The interior of the Earth
A great amount of heat
also comes from buried hot
rocks and lava flow from
craters and crevices of
erupting volcanoes.
The hot spring in Tiwi, Albay, Los Banos, Laguna and
in Tayabas Quezon are proofs that the earth’s interior is
much hotter than its surface.

8. Artificial Sources
1. Chemical Action
When fuels like coal, kerosene, wood, and gasoline are
burned, they are used as artificial sources of heat.
The oxygen we breathe in
burns the food we
eat, producing enough body
heat to keep our body
temperature close to 370 C.

9. 2. Mechanical Action
Heat energy produced by a friction.

10. 3. Electrical Energy
Electricity is a very common source of heat at
home.
Oven toaster and electric iron are heated by the
resistance of the heating coils to the electricity
passing through them.

11. 4. Nuclear Energy
The tremendous
amount of energy
from nuclear
reactions can be used
to change water into
steam, which is then
used to operate a
turbine to generate
electricity.

12. How much have you learned?
1. Heat is one of the topics in Thermodynamics.
What is thermodynamics?
2. Use kinetic molecular theory as a basis to explain
how heat is produced.
3. Solar energy is used by plants to manufacture
their own food. Give two other examples how
solar energy is used.
4. Make a short description of the following kinds
of thermometer:
A. liquid-in-glass thermometer
B. Platinum-resistance thermometer
C. Thermocouple
D. Optical
E. thermograph

13. Temperature Scale
The most common thermometer used in the
laboratory is the Mercury Thermometer.

14. Colored alcohol is another liquid commonly used in
thermometer.

15. Celsius Scale
Commonly known as Centigrade Scale
This scale was devised in
1741 by a Swedish
astronomer, Anders
Celsius, based on the
properties of water.

16. On the Celsius scale, the freezing point of
water is fixed at 0 degree Celsius (00 C)
The boiling point of pure water under
normal atmospheric pressure, 760 mm
Hg (at sea level), is 100 degrees Celsius
(1000 C).
The normal temperature of the human
body is 370 C

17. Fahrenheit Scale
The Fahrenheit scale was
devised by Daniel Gabriel
Fahrenheit, A German
physicist.
Unites States of America and England use the
Fahrenheit scale for weather observation and other
purposes.

18. On Fahrenheit scale, 320 F is
the freezing point of water and
2120 F is the boiling point.

19. Kelvin Scale or Absolute Zero
Named after Sir
William Thompson
(Lord Kelvin) who
devised it.

20. This temperature scale is often used when
gases are involved.
Its zero point (0 K) corresponds to -2730 C
and is referred to as Absolute Zero or the
temperature at which the molecular
energy of matter is minimal.
On the Kelvin scale, the freezing point of
water is 273 K and the boiling point of
water is 373 K.

22. To convert temperature readings from
one scale to another, the equation below
are used:

23. Converting Units of Temperature
oC to oF oF = (9/5)( oC) + 32
38.7 oC oF
oF = (1.8)(OC) + 32
= (1.8) (38.7) + 32
= 69.66 + 32
= 101.7

24. oF to oC oC = 5/9 ( oF – 32)
101.7 oF o C
oC = 5/9 ( oF – 32)
= .555 (101.7 – 32)
= (.555) (69.7)
= 38.7

25. oC to K K = 273 + oC
38.7 oC K
K = 273 + oC
= 273 + 38.7
= 311.7

26. Convert the following
1) 37o C to oF 1) 98.6oF
2) 350oF to oC 2) 176.7oC
3) 100oC to K 3) 373 K
4) 95o C to oF 4) 203 oF
5) 130oF to K 5) 327.4 K
6) 39oC to oF 6) 102 oF
7) -160oF to oC 7) -107oC
8) 80.0oF to oC 8) 27 o C
9) 27oC to K 9) 300 K
10) 120oC to oF 10) 248 oF

27. How Heat is Measured?
Thermometer only gives us an idea of the total
potential energy and kinetic energy of the molecules
in an object.
It does not tell us how much heat a particular object
absorbs or gives off.
In fact there is no instrument that directly measures
the amount of heat energy that a body gives off or
absorbs
If you want to calculate the amount of heat given off
by a piece of charcoal or a certain kind of gas, then
you have to determine the change in temperature it
produces on a definite volume of water.

28. Units of Heat
Common units used for measuring heat energy:
a. Calorie (cal)
b. kilocalorie (kcal)
c. joule (J)
The SI unit for heat, as for any other form of energy is
the Joule (1 N.m = 1 joule)
Today, the calorie is defined in terms of the joule: that
is 1 cal = 4.184 J.
This is the mechanical equivalent of heat
1 Kcal = 1000 calories

29. Effects of Heat
1. Generally when a substance absorbs heat, its
temperature rises.
2. Solid usually melt or change to the liquid
state when heated.

30. 3. Liquid may absorb enough energy when
heated to change to vapor state.

31. 4. Almost all objects expand when heated.

32. 5. A change in the heat content of a substance
can cause chemical changes.

33. 6. Heat causes many changes in bodily
functions of living organisms
Enzymes are protein-like substances formed in human
cells that act as catalysts in initiating or speeding up
specific chemical reactions.
Each has a characteristics shape that allows it to hold
two or more molecules close enough together so they
can react chemically.
If the temperature is increased, then the speed of
moving molecules is also increased.
Bombardment by high speed molecules in the cell can
cause the enzymes to lose its shape.
It can no longer perform its vital function.

35. Two glasses stack together.
If we twist them apart, one or both
of them may break.
What is the safest way to separate
the two glasses that stick together?
One way is to pour some cold water
into the inner glass and dip the
outer glass in hot water.
Within a short while, the two glasses can easily be
pulled apart.
Why? Generally most substances expands when
heated and contract when cooled.

36. A change in temperature produces
a change in length in almost all
solid.
Experimental results have shown
that change in length is directly
proportional to change in
temperature and to the original
length of the object.
Different solids of the same length
differ in their expansion for the
same change in temperature.

37. In liquids the effect of heat is an increase in their
volume while the effect of cooling is a decrease in their
volume.

38. Expansion of Gases
Why do gases
expand at a greater
rate than solids and
liquids?

39. Change of Phase
Whenever the temperature of a substance
changes, there is an accompanying change in its
molecular structure.
If the change in molecular structure is such that it
becomes noticeable, then we say that the substance
is undergoing a Change of Phase.

42. Heat Transfer
Heat may be transferred in
three ways:
a. Conduction
b. Convection
c. Radiation

43. a. Conduction
Transmission of heat from particle to particle
Conduction of heat in an object will take place
only when one part of the object has a higher
temperature than another part.
The part with a higher
temperature will transfer its
heat energy to that part
with a lower temperature.

45. Solid are the best conductors of heat.
Among solids, metal conduct heat
the best.
But metals differ in their
conductivity.
Silver is very good conductor of heat
than iron and lead. Why?

46. b. Convection
The heat energy is distributed by the liquid or
gaseous molecules in circling currents.

47. c. Radiation
Transfer of heat through electromagnetic
waves.

48. 2
1
3
4

49. QUIZ

50. 1. The absolute zero temperature
is _____
a. -273 0 C
b. -320 C
c. 00 C
d. 273 K

51. 2. The space between the walls of
the double-walled thermos bottle
is evacuated to ______
a. increase volume
b. reduce convection
c. reduce heat transfer by
conduction
d. both b and c

52. 3. Dry ice has a temperature of -
110.2 0 F. What would its
temperature be on the Celsius
scale?
a. -7110 C
b. -198.3 0 C
c. -142.2 0C
d. -79 0C

53. 4. Room temperature is often
0
identified as 68 F. What
temperature is this on the Kelvin
scale?
a. 20 K
b. 100 K
c. 293 K
d. 341 K

54. 5. The transfer of energy from a
source to an object by direct
contact between them is _____
a. conduction
b. convection
c. insulation
d. radiation

55. 6. As more heat is added to a
sample of water boiling in a
stove, its temperature ______
a. decreases
b. increases
c. increases then decreases
d. remains the same

56. 7. When water reaches 4 0 C, ____.
a. it will expand only if heated.
b. its volume will remain constant.
c. it will expand whether it is cooled
or heated.
d. it will contract until it freezes into
ice, and then expand.

57. 8. When does vaporization
happen? It _____________.
a. will occur only at night.
b. takes place at very great pressures.
c. occurs at the boiling point temperature
d. takes only at a definite temperature
may occur at a definite temperature
or at any temperature.

58. 9. Which of the following
statements is true about boiling?
It ____________.
a. is lower than evaporation.
b. takes place at a definite
temperature.
c. is the same for all liquids at the
same temperature.
d. takes place when bubbles begin to
appear in the liquid.

59. 10. The rate of evaporation may
be increase by _______
a. raising the temperature of the
liquid.
b. increasing the surface area of the
liquid.
c. decreasing the air pressure on the
surface of the liquid.
d. any of the above.

60. 11. What is condensation? It ____
a. is an exothermic process.
b. is the opposite process of
melting.
c. is due to the increase in the
kinetic energy of the particle
of the liquid.
d. refers to the change from solid
state to gaseous state form of
matter.

61. Two cars of the same model, the same brand, and the
same size, are both locked and parked under the sun
in an open parking lot. The two cars are parked
from 9:00 A.M. to 5:00 P.M. One of the cars is ivory
white in color and the other is dark blue.
12. Under the same condition, at 12:00 noon, _____
a. the dark-colored will be hotter inside.
b. the ivory-colored car will be hotter inside.
c. since both are locked, the sun will not affect
either car.
d. since both are under the same sun, they will
both be equally hot.

62. Match Column A with Column B
Column A
Column A
_____13. William Thompson a. Centigrade tempt. Scale
_____14. Anders Celsius b. Absolute Tempt. Scale
_____15. D. Gabriel Fahrenheit c. Fahrenheit Tempt. Scale
_____16. B.T. Rumford
_____17. J. Prescott Joule d. Heat is produced by friction
e. Concluded that heat is a
form of energy.

63. 18-21. Enumerate the different
artificial sources of heat.
18.
19.
20.
21.

64. 22-24. Enumerate the different
methods of heat transfer.
22.
23.
24.

65. 25. True or False
Land breeze and sea breeze
occurs because of conviction current.

66. Answer

67. 1. The absolute zero temperature
is _____
a. -273 0 C
b. -320 C
c. 00 C
d. 273 K

68. 2. The space between the walls of the
double-walled thermos bottle is
evacuated to ______
a. increase volume
b. reduce convection
c. reduce heat transfer by
conduction
d. both b and c

69. 3. Dry ice has a temperature of -110.2
0 F. What would its temperature be
on the Celsius scale?
a. -7110 C
b. -198.3 0 C
c. -142.20 C
d. -79 0C

70. 4. Room temperature is often
0
identified as 68 F. What
temperature is this on the Kelvin
scale?
a. 20 K
b. 100 K
c. 293 K
d. 341 K

71. 5. The transfer of energy from a
source to an object by direct
contact between them is _____
a. conduction
b. convection
c. insulation
d. radiation

72. 6. As more heat is added to a
sample of water boiling in a
stove, its temperature ______
a. decreases
b. increases
c. increases then decreases
d. remains the same

73. 7. When water reaches 4 0 C, ____.
a. it will expand only if heated.
b. its volume will remain constant.
c. it will expand whether it is cooled
or heated.
d. it will contract until it freezes into
ice, and then expand.

74. 8. When does vaporization
happen? It _____________.
a. will occur only at night.
b. takes place at very great pressures.
c. occurs at the boiling point temperature
d. takes only at a definite temperature
may occur at a definite temperature
or at any temperature.