Introduction Why there must be a gap between two rail bars (rail way track)?

EXPANSION SCIENCE TEAM P26

Expansion SolidLiquidGas Linear Area Volume

Illustration of particle’s movement Solid Particles Liquid Particles Gas Particles When the particles are heated, which one will expand faster?

Solid Expansion The bridges on the roads are generally made of steel which are connected to each other. During the process of constructing the bridge, construction engineers consider the nature of expansion and contraction of the steel because of temperature changes, either at noon or night. There is a gap on the bridge

Solid Expansion Solids will expand when it is heated and contract when it is cooled. Expansion happens because the atoms of an object vibrate faster than usual, so that its volume is bigger and its density decreases.

Linear Expansion of Solid L O LtLt LL Before being heated When being heated The length change influence by: 1.The length of an object 2.The change of temperature 3.Kind of matter (material)

Linear Expansion The Formula of linear Expansion. For α = coefficient of linear expansion. L o = The first length of the object ∆T= The change in temperature ∆L= The change in length ΔL = L – L o ∆T = T – T o

EXCERCISE Example: A train track which is made of steel has the length of 40 meters on 0 o C. How long is its expansion if it is heated until 100 o C? Known Lo= 40 meters ∆T= 100 o C - 0 o C = 100 o C αsteel= / o C Question: ∆L = ? Equation: ∆L = Lo. α. ∆T Solution: ∆L = ( / o C) (40 meter) (100 o C) = meter

EXCERCISE The length of plastic is 20 cm at 20 o C and when the temperature rise at 140 o C, the plastic is longer be 80 cm. How the plastic linier coefficient is? By the question knowed:T 0 = 20 o C T = 140 o C L 0 = 20 cm L = 80 cm Asked:  ? Answer:L = L 0  1+  (T-T 0 )  80 = 20  1+  (140-20)  4 = 1 + . 120  = 0,025 o C -1 So that, the linier coefficient of length expansion is 0,025 o C -1

Area Expansion

Area expansion in solid The area expansion coefficient is twice the linear coefficient. The formula of area expansion : The Formula of Area Expansion. For β = coefficient of area expansion. A o = The first area of object ∆T= The change in temperature ∆A= The change in area β = 2.α

Volume Expansion

Volume expansion in solid The volume expansion coefficient is three times larger than the linear expansion coefficient. The formula of volume expansion is The Formula of Volume Expansion. For γ = coefficient of volume expansion. V o = The first volume of the object ∆T= The change in temperature ∆V= The change in volume γ = 3.α

The examples of the use of expansion or contraction in daily life is 1. Bimetal. Brass Steel Bimetal is heatedBimetal is cooled

Bimetal Bimetallic Strip: Brass,  = 19 x /C o Steel,  = 12 x /C o

Bimetal Thermostate

*Thermostat is a device which keep a building, engine,etc, within a ussualy limited temperature range, by automatically switching on-off. * Bimetallic strip is a strip used in thermostat, made of two different metals which expand with different amount, when it heated. *The principle of bimetal is based on the different linier expansion coefficient of two metals are packed each other. The function of a bimetal as automatic switch

1. Bimetal 2. thermostat 3. automatic switch in an electric iron 4. the track of the train and 5. bridge connectors are given a space. Application of Solid Expansion

Main Activity Indicator Metal Bar Burner Screw Musschenbroek Apparatus

MUSSCENBROEK

Musschenbroek Apparatus It can be used to find the increasing length (expansion of different metals) when being heated.

Data and observation Not move Move 5 scale 10 scale 6 scale Which one is the longest metal when being heated? Aluminum Why does the aluminum have the longest linear expansion?

Conclusion “Expansion is increase in size of a matter, if it heated. 3 Kinds of expansion are solid expansion, liquid expansion, and gas expansion.”

The length change is influenced by: 1.The length of an object 2.The change of temperature 3.Kind of matter (material) It can be formulated as follows:

. EXCERCISES Answer these questions correctly! 1.Why a gap is given between rail road ? 2.What is bimetal? 3.What is the function of bimetal in a electric iron? 4.What is the function of thermostat ? 5.Can you mention the working principle of thermometer? Good luck!

Excercise! 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. Given linear expansion coefficient of iron is /C˚!