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Expansion

 

When an object is heated it increases in size.

Increase in size on heating is known as Expansion .

 

Example 1

 

  • Fixing the iron blade of the soil digging tool with a wooden handle.
  • The iron blades of these tools have a ring in which the wooden handle is fixed.
  • These rings are slightly smaller in size than the wooden handle.
  • To fix the handle with the ring, the ring is heated.
  • When heated,the ring becomes slightly larger in size(Expands).
  • Now the handle fits easily with the ring.
  • When the ring cools down it contracts and fixes tightly with the handle.

 

Example 2

  • Fixing a metal rim to a wooden wheel.
  • Again in this the metal rim is made slightly large r than the wooden wheel
  • To fix the metal rim to a wooden wheel.
  • We need to heat the metal rim .
  • On heating the metal rim increases in size.
  • And fixes easily to the wooden wheel.
  • On cooling , the metal rim fixes tightly on the wooden wheel.

Contraction

 

  • When the object is cooled , it decreases in its size
  • Decrease in size on cooling is known as Contraction.

 

Evaporation of Water

 

  • When water is boiled ,it changes into steam(water vapor)
  • If we cool the steam it forms water again .
  • Thus,this process of boiling of water is a reversible change.

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CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Economics, Accounting and English at Teachoo