SCIENCE 8 TEMPERATURE & HEAT

2. “ ” and “ ” are used everyday to describe the
temperature of an object.
However, these words mean differently to different people.
To better understand the concept of temperature, imagine
a glass of water on top of the table.
It may seem that water is not moving, but the water
molecules that make up the water are moving at different
speeds and in random direction.

3. • Measure of the average value of the kinetic energy of the
molecules in random motion.
• More kinetic energy of the molecules, the higher the temperature
gets, the faster the rate of motion
• Thermometer is used to measure temperature.

4. • STANDARD SCALES are used to measure the temperature of an object
in a thermometer.
• Two most commonly used scales are:
1. Celsius Scale – more widely used around the world. Freezing point of
water is 0oC, and boiling point of water is 100oC. Δ of 1Co > Δ in 1Fo.
2. Fahrenheit scale – mainly used in US, some territories like Puerto
Rico, Guam, and Virgin Islands. Water freezes at 32oF and boils at
212oF.

5. • Kelvin scale – another scale used and based on absolute zero.
is the lowest possible temperature where the molecules and an
object are at minimum speed. 0K is equal to -273OC.
• Equation in converting temperatures from one another:
a.) oC = 5/9 (oF -32o) d.) oF = 9/5 (K-273) +32
b.) oF = (9/5 x oC) + 32 e.) oC = K - 273
c.) K = oC + 273

6. • Kinetic energy is transferred from higher temperature to lower
temperature.
• EX: picking up a glass of iced soda. You will notice that the soda slowly
warms up. Since soda is colder than your hand, the molecules in the soda
have a lower kinetic energy than that of your hand. Hence, the molecules
from your hand is transferred to the soda wherein there is a collision
between the molecules. Eventually, the heat flows out of your hand and
into the glass of soda. The temperature of the skin of your hand decreases
while the temperature of the soda increases. Heat will stop flowing as soon
as the temperature of the hand and the glass of soda is the same.

7. • Temperature changes leads to the expansion or contraction of the
object.
• Heat is absorbed = materials expand; Heat is released = materials
contract
• This happened because once the material is heated the molecules
moves faster and move speedily, thus a need of extra space in
order for them to move much apart from each other.

8. 1. LINEAR EXPANSION
2. VOLUME EXPANSION

9. • Expansion depends on the change in temperature, original length, and the
type of material of which it is made.
• Solids expands linearly with the change in temperature.
Mathematical equation:
∆L = αLi ∆T
α = coefficient of the object expressed in per Celsius degree (Co)
∆L = change in length in meters (∆L = Lf – Li)
Li = original length of the object
∆T = change in temperature in Co (∆T = Tf – Ti)

10. COEFFICIENT OF LINEAR EXPANSION OF SOME
MATERIALS
Substance α (x 10-6 /Co) Substance α (x 10-6 /Co)
Aluminum 24 Gold 14
Brass 19 Quartz 0.77 – 1.4
Concrete 0.7 -1.2 Silver 20
Copper 17 Steel 13
iron 12 tungsten 4.3

11. EXAMPLE:
G: αsteel = 13 x 10-6
∆T = Tf – Ti = 40oC – (-15oC) = 55 Co
Li = 1275 m
S: ∆L = αLi ∆T
= 13 x 10-6/ Co (1275 m)(55 Co)
= 0.016575 m/ Co (55 Co)
= 0.911625 m
A: The change of length of the bridge is 0.911625 m at
its highest temperature(warmest).
The main span of San
Francisco’s Golden Gate
Bridge is 1275 m long at its
coldest. The bridge is
exposed to temperatures
ranging from –15ºC to 40ºC.
What is its change in length
between these
temperatures? Assume that
the bridge is made entirely of
steel.

12. • As materials become warmer, they expand uniformly in all
directions, therefore their volume increases also.
• Formula: ∆V = βVi ∆T
Vi – initial volume
∆T – change in temperature
β - coefficient of volume expansion
β = 3 x α

13. COEFFICIENT OF VOLUME EXPANSION OF SOME
MATERIALS
Substance β (x 10-6 /Co) Substance β (x 10-6 /Co)
Ethyl alcohol 1100 mL mercury 182 mL
gasoline 950 mL turpentine 970 mL
glycerin 500 mL water 207 mL

14. EXAMPLE:
G: β = 3400 × 10– 6
Vi = 500 m3
∆T =20oC – 0oC = 20 Co
S: ∆V = βVi ∆T
= (3400 x 10-6 / Co) (500m3)(20 Co)
= 34 m3
A: The difference in volume if there is 0oC temperature
is 34m3.
There are 500 m3 of air in
a shop at 20°C. What is
the difference in volume
if the temperature is
0°C?