Expansion solid

Apperception

• Why is a space left between the railway line where one piece joins the next?

Thermal Expansion

Objective

Investigating thermal expansion in solid

Activity

Using your Student Worksheet Using your Student Worksheet 11.611.6

(page 129)(page 129)

Do the experiment in your Do the experiment in your groupgroup

Summary

• Solid expand when they are heated, and decrease in volume when they get colder.

• From a microscopic point of view, the result of heating a material can be explained as follows:– There is an addition of energy to the material– The internal energy of the atoms of the

material increase, causing atoms to vibrate– The vibrating atoms now occupy more space

when hot compared to when cold.

Thermal Expansion

Expansion of solid

Expansion of liquid

Expansion of gas

Linear expansion

Area expansion

Volume expansion

l= lo. . t A= Ao. . t V= Vo. . t

Linear Expansion

lo

l

lt

Linear Expansion

• The magnitude of the thermal expansion of the solid depend on :– Type of solid– Temperature rise– Length

Linear Expansion

• The expansion of solid body is proportional to the temperature rise and to its length

We can make Formula

l lo t

Summary

Or We can write in equation of thermal expansion:

l = lo t

l = change in length (m) = coefficient of thermal expansion

(oC1)lo = Initial length (m)

t = change in temperature (oC)

Summary

• On a hot day, the metal expands and if it were not allowed to do this, the rails would bend out of shape.

• This has caused railway accident in the past.

click

Area Expansion

AoA

At

Area Expansion

We can make Formula

A Ao t

Summary

Or We can write in equation of thermal expansion:

A = Ao t

A = change in Area (m2) = coefficient of thermal

expansion (oC1)Ao = Initial Area (m2)

t = change in temperature (oC)

click

Volume Expansion

Vo V

Vt

Volume Expansion

We can make Formula

V Vo t

Summary

Or We can write in equation of thermal expansion:

V = Vo t

V = change in Volume (m3)

= coefficient of thermal expansion (oC1)

Vo = Initial Volume (m3)

t = change in temperature (oC)