Changes Around Us,CBSE Class 6 NCERT Solutions, Free NCERT solutions for Changes around us


Chapter 6

Changes around us

We can see so many changes around us happening, like the changing of the seed to plant in the field or in our environment, hair growth, growth of the nails, milk to curd, egg to omelets, etc. Some changes can be reversed and some can not be reversed and the processes are called the reversible processes (changes can be reversed) and irreversible processes (changes can not be reversed).

For Example à Take a balloon and blow the air, the balloon will expand and when you release the air balloon come to its previous shape if not burst.

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Inflation and Deflation of a Balloon (An example of reversible change) 

Some examples of reversible and irreversible processes

Dough àRoti à Dough  ✔ 
Batter à Idli à  Batter  
Woolen Yarn àKnitted Sweater à Woolen Yarn  ✔ 
Cold Milk à Hot Milk à Cold Milk  ✔ 

Have you seen the metal tools?

The metal in these tools is transferred by softening the metal by heating at high temperatures. The metal expands when heated and can easily be fitted in a wooden handle and when the metal is cooled it will hold the wooden handle tightly.


Changes around us, metal on wooden handle, ncert 6th class
Fixing the hot metal in the wooden handle

In Bullocks carts, the rim is fixed on the wooden wheel by the same process of heating of the metal.
Changes around us, ncert 6th class, bullock cart, bullock cart wheel,
Transfer of Metal on the wooden wheel

Candle Lighting
When we lighten a candle, we can see the melting of the candle with time. The burning of string in the candle is irreversible as we can reverse this change and the burning of wax is somewhat can be reversed but to a smaller extent. 

NCERT 6th class changes around us, burning of candle, lighting of candle, free solution class 6th ncert
Burning of candle


Could it be reversed? Yes, if we heat the wax we can make candles again.

Exercise:

1. To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this change be reversed?
Answer: Of course, this change is reversible as we can unfold our clothes again.

2. You accidentally dropped your favourite toy and broke it. This is a change you did not want. Can this change be reversed?
Answer: This change is irreversible.

3. Some changes are listed in the following table. For each change, write in the blank column, whether the change can be reversed or not.


S. No.
Change
Can be reversed (Yes/ No)
1
The sawing of a piece of wood
No
2
The melting of ice candy
Yes
3
Dissolving sugar in water
No
4
The cooking of food
No
5
The ripening of a mango
No
6
Souring of milk
No


4. A drawing sheet changes when you draw a picture on it. Can you reverse this change?
Answer: This can be reversed if we write with a pencil or any other objects which can be erased, but it is irreversible if we write with a pen.

5. Give examples to explain the difference between changes that can or cannot be reversed.
Answer:
Reversible Changes are those changes which can be reversed, for example, freezing of water into ice and ice can be melted again into water.

Irreversible changes are those changes which cannot be reversed for example curdling of milk; we cannot make milk out of curd again.

6. A thick coating of a paste of Plaster of Paris (POP) is applied over the bandage on a fractured bone. It becomes hard on drying to keep the fractured bone immobilised. Can the change in POP be reversed?
Answer: The change in POP cannot be reversed, when powered POP is mixed with water and applied a chemical reaction change this liquid form into solid form and this reaction after solidification can’t be reversed.

7. A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?
Answer: This change is cannot be reversed as the chemical reaction which occurs in cement on the addition of water is completed and we cannot make cement usable again.

Keywords: Changes, Contraction, Evaporation, Expansion, Melting, NCERT, CTET Paper-II, CTET TGT, KVS, NCERT 6th class science changes around us.



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