Concepts

Class 6
Chapter 6 Class 6 - Changes around us

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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