THERMAL EXPANSION
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 Standard Competency:
 Understanding state of matter and their change
 Basic competence
 Doing experiment relate to expansion and apply in daily
life.
 Indicator to achieve competence
 To take simple experiment for showing expansion in solid,
liquid and gas.
 Find expansion process, in solid, liquid and gas.
 To show expansion in solid, liquid, gases, and their
technology
Glossary
 Heat = Panas
 Heated = dipanaskan
 Cooled = didinginkan
 Expansion = Pemuaian
 Expand = Memuai
 Contraction = penyusutan
 Contract = Menyusut
 Linear expansion coefficient = Koefisien muai panjang
 Area expansion coefficient = Koefisien muai luas
 Volume expansion coefficient = Koefisien muai volume
Why a gap is given between rail roads?
Why bridge connectors are given a space?
Expansion
Solids will expand when it is heated and contract when
it is cooled.
Expansion is INCREASE in size when an object is
heated.
When heated, the atoms and molecules of the matter will
vibrate faster than usual because of the high temperature
Therefore
Atoms and molecules
need more space then
the matter will expand
to any direction
1. Linear Expansion
l0
Δl
2. Area Expansion
A
ΔA
3. Volume Expansion
Thermal
Expansion
Expansion
of solid
Linear
expansion
Area
expansion
Expansion
of liquid
Volume
expansion
Expansion
of gas
Linear Expansion (pemuaian panjang)
Influences by:
1. Kinds of Solid
2. The length of an object
3. The change of Temperature
Linear Expansion coefficient (α)
•is a value that states the rate of an expansion speed of an object per
temperature degree
•The Higher linear expansion coefficient of an object is, the faster the
object will expand
Linear Expansion
lo
lt  lo  l
l
lt
l    lo  T
lt= Final length (m)
lo= Initial length (m)
Δl = length expansion (m)
α= Linear expansion coefficient (/ C ˚)
ΔT= Changes of temperature(C ˚)
Example 1:
1. A steel railway track is 40 metres long at 0 °C. How long is its
expansion if it is heated up to 100 °C? (αsteel = 0.000011/C°)
Given :
lo = 40 m
T1 = 0 °C
ΔT = T2 -T1 = 100 C°
T2 = 100 °C
αsteel = 0.000011/C°
Question: Δl
Answer
Δl = α. lo . ΔT
= 0.000011/C° . 40 m . 100 C°
= 1.1 x 10-5 .4 x 101 . 1 x 102 m
= 4.4 x 10-2 m
= 0.044 m
A steel bridge is 100 m long at 20 °C. What is the final
length if its heated until 80 °C?(α steel is 0.000011/ C
°)
Exercise
1. A copper bar at 15°C is 20 metres long, then it is
heated up to 35°C. Determine how much its length will
expand during the heating process if its expansion coefficient
is 0.000017/ C°.
2. An iron bar at 20˚C is 3 meter long, and then it is heated up to
100˚C. Determine the final length of bar if linear expansion
coefficient (α) is 0.000012/C˚?
3. A Pyrex glass with initial length of 5 meters is heated up 50Co
from initial temperature. Determine the length expansion of
that glass if its length expansion coefficient is 0.000004/C0.
4. The length of steel bar (α= 0.000012/C°) at temperature of
30°C is 50 cm. If the length of that steel bar becomes 50.011
cm, the temperature increase is
5. You’re heating a 2.5 m lead bar, coefficient of linear
expansion
2.9 × 10–5 /C°, raising its temperature by
40C°. What is the
final length of the bar?
Answer these questions correctly!
1. What is expansion? Explain.
2. Give 3 examples of expansion in daily life!
3. When do the objects expand? Explain.
4. Mention the factors that influence expansion!
5. What kind of formula to find the changing of length of linear
expansion!
6. What instrument do you use to find the linear expansion?
7. The initial length of iron is 30 m at 25 ˚C. if it’s heated up to 90
˚C. Determine the length of iron after being heated. (linear
expansion coefficient of iron is 0.000012 /C˚)!
At = Ao +A
At
Ao
A

Ao
T
A =  x Ao xT
A
= change in Area (m2)
= Area expansion coefficient (/Co)
= Initial Area (m2)
= change in temperature (Co)
= 2α
Vt = Vo + V
Vt
Vo
V =  Vo t
V


= 3α
=
/C°
For solid
All gas
V = change in Volume (m3)
 = Volume expansion coefficient (/Co)
Vo = Initial Volume (m3)
T = change in temperature (Co)
LINEAR EXPANSION
AREA EXPANSION
VOLUME EXPANSION
l
THERMAL
EXPANSION
A
Δl
0
0
ΔA
l    lo  T
lt  lo  l
A    Ao  T
At  Ao  A
For solid 
 2 
ΔV
V0
V   Vo  T
Vt  Vo  V
  3
For solid
1

For Gas 273C 
1. A plate of glass measures 100 m long and 50 m wide at
20 oC. What is its final area if the temperature is
increasing until 70oC? (α = 0.9 x 10-5/C°)
2. A 200 cm3 Alcohol is heated from 25oC to 75 oC.
Calculate the volume expansion of alcohol if volume
expansion coefficient of alcohol is 0.0012 /Co.
3. Volume of kerosene at 5oC is 2 liter. If its heated until
105oC, how much the final volume of kerosene? (ɤ of
kerosene is 0.000955 /Co).
4. The volume of glass cylinder at 10 oC is 1 liter. It’s full with
alcohol. How much the spilled alcohol if it heated until 60
oC? (α glass = 0.000009/Co ; ɤ alcohol = 0.00120 /Co )
(spilled = tumpah)
The examples of the use of expansion or
contraction in daily life
1. Bimetallic strip

Bonding two metals with dissimilar thermal expansion coefficients

What will happen if we heated bimetallic strip?


Bimetallic will bend to metal with the smallest
linear expansion coefficient
Example:
Bimetallic strip which consist from brass and steel.
Bimetallic strips will bend to steel direction, because:
α brass = 1.9 x 10-5/C°
α steel = 1. 1x 10-5/C°
α brass > α steel
HEATED
α copper > α iron
Bimetallic strips will bend to iron direction
CONCLUSION:
Bimetallic strips will bend to metal with the
smallest linear expansion coefficient
Bimetallic strips can be found on…
T-Bimetal Thermometer
Thermostat
Automatic switch in an electric iron
Fire Alarm
Automatic switch
FIRE ALARM
The examples of the use of expansion or contraction
in daily life
2.
Thermometer
3.
4.
Metal plates riveting (Pengelingan pelat logam)
Installation of metal rims on wheels
(Pemasangan bingkai logam pada roda)
5.
Railway track joint (Sambungan rel kereta api)
6.
Expansion joint on a bridge (Celah pemuaian pada logam)
If a gas has a constant mass and is held at a constant pressure then the volume divided by the
temperature is a constant value.
The relationship between
temperature and volume at
constant pressure
V1 V2

T1 T2
Note:
V1 = Initial Volume
V2 = Final volume
T1 = Initial Temperature (Kelvin)
T2 = Final Temperature (Kelvin)
Example :Problems of Charles’s Law
1. The initial volume of a gas in piston is 100 cm3 and its
temperature is 327°C. If the volume decrease until 50 cm3
while the pressure is constant, temperature of gas will
become…
Given
:V1 = 100 cm3
V2 = 50 cm3
T1 =
327 °C
Question
: T2 = ??
Answer : First, Convert Temperature into Kelvin scale:
T1 = (327+273) K = 600 K
V1 V2

T1 T2
100cm3 50cm3

600K
T2
100cm3  T2  50cm3  600 K
50cm3  600 K
T2 
 300 K
3
100cm
T2 = (300-273) °C = 27
°C
1. Gas volume at temperature of 27°C is 20 liters. If gas
is heated in constant pressure, the volume of the gas
when its temperature 127°C is….
2. A 250 cm3 sample of neon is collected at 47
oC. Assuming the pressure remains constant, what
would be the volume of the neon at 207 oC?
3. The initial volume of gas in a piston is 400 cm3 and its
temperature is 600 K. If half of the gas volume is
reduced at the constant pressure, its temperature is…
 Most substances expand when heated and contract when
its cooled, but water is unusual
4°C  0°C (cooled)  the water will expands
0°C  4°C (heated)  the water will contracts
 Beside that range of temperature, water will experience
normal expansion.
 This phenomenon makes water have the
smallest volume at temperature of 4°C
 Thus, water will have the biggest density at 4°C
 The anomalous expansion of water helps preserve
aquatic life during very cold weather.
 When temperature falls, the top layer of water in a pond
contracts, becomes denser and sinks to the bottom. A
circulation is thus set up until the entire water in the pond
reaches its maximum density at 4°C. If the temperature
falls further, the top layer expands and remains on the top
till it freezes. Thus even though the upper layer are frozen
the water near the bottom is at 4°C and the fishes etc.
can survive in it easily.