Changes around us -Reversible-Irreversible changes

Changes

We see and observe many changes around us without any magic. For example,the trees are growing, the flowers bloom and wither away, We grow, seasons change and many changes are there around us.The changes around us can be categorized or classified into many types.

Some changes can be reversed by us, such changes are called reversible changes.For example- A balloon once inflated can be deflated, a folded paper can be made a full paper, a clay can be molded again and again till it dries. Some changes which cannot be reversed are called as irreversible changes, for example a balloon if burst once cannot be inflated again, a paper cutout made from a full paper cannot be made back a full paper again, a molded dough if converted into chapati cannot be again made dough..

1. Describe a change?

Answer- A change is change in terms of size, color, state, position, shape or anything. It can be of any form, either done by nature or by us.

2. What is a reversible change? Give one example of it?

Answer- A Change that can be reversed after the change has been done is called a reversible change. Eg. water converted into ice, we can get water again.

3. What is an irreversible Change? Give an example of it?

Answer- An irreversible change is the change in which we cannot get back the original product after the change has been done.For Eg. A paper if burnt converts into ash and we cannot get the paper back.

Reversible and Irreversible Changes

1. Give at least 5 examples of reversible changes.

Answer- Examples of Reversible changes:

a) Inflating and deflating a balloon.

b) Folding a paper then unfolding it.

c) Converting ice to water and back.

d) A molded clay converted to a toy and then again converted to clay back.

e) A woolen yarn converted to sweater by knitting.

2. Give at least 5 examples of irreversible changes.

Answer- Examples of Irreversible Changes:

a) Burning of Paper.

b) Deflating a balloon by bursting it.

c) Converting milk to Curd.

d) Breaking of Glass.

e) Dough of flour converted to chapati by baking.

3. What all are the changes that happen when we burn a paper?

Answer- When we burn a paper, its color changes to grey or black, It converts into ash (Powder), and it smells bad(burning smell) while burning. In all a paper after burning changes to ash and it is a irreversible change.

4. What are the ways through which we can bring a change?

Answer- We can bring a change in many ways, By striking the thing hard, by breaking it, by pushing it, by burning it, by coloring it, by molding it, by cutting it, by chopping it, by heating it, by cooling it, by treating it with chemicals and by many other ways.

Fill In The Blanks:

1. Burning of a paper is a kind of reversible change.

2. Changing of milk into curd is an example of irreversible change.

3. We can convert ice into water and water into ice. It is an example of reversible change.

4. To change wheat flour to chapati, we mix wheat flour with water to make dough and then dough is molded in the form of Chapati and heated on the pan to make chapati. this change is a type of irreversible change.

5. A change in which we can get back things mixed in their original shape, size and color is called a reversible change, while the change which cannot be reversed is called irreversible change.

Exercise Questions:

To walk through a waterlogged area, you usually shorten the length of your dress by folding it. Can this be changed?

Answer- Yes, by unfolding the dress this change can be reversed.

You accidentally dropped your favorite toy and broke it. This is a change you did not want. can this change be reversed?

Answer- No it cannot be reversed, so it is a reversible change.

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?

Serial 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 mango	No
6	Souring of milk	No

Answer-

Serial 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 mango	No
6	Souring of milk	No

A drawing sheet changes when you draw a picture on it. Can you reverse this change?

Answer- A drawing sheet changes when we draw a picture on it. This change can be reversed if picture is drawn using pencil only by erasing the picture drawn. But if the picture is drawn using colored pen or pencils, it cannot be reserved.

Give examples to explain the difference between changes that can or cannot be reversed?

Answer- Examples of changes that can be reversed- A rubber band stretched , a paper folded, water freezes to make ice.

Examples of changes that cannot be reversed- A rubber cut into many parts, a paper folded and teared into many pieces, Milk mixed in water.

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 immobilized. Can the change in POP be reversed?

Answer- No, The POP if hardened cannot be got back. Hence the process is irreversible.

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- No, if cement is once set, it cannot be converted into cement back. Hence the change which occurs in cement cannot be reversed.

Key Words (Changes Around Us)

1. Changes: Any kind of conversion in Shape, Size, Form, Position or Location of an object is called Change.

2. Contraction: Changes in which the size of the objects gets reduced is called Contraction.

3. Evaporation- Process in which water gets converted into vapor when heated is called Evaporation.

4. Expansion- Change in which size of the object increases is called expansion.

5. Melting- Process in which object converts into its liquid form due to heating is called Melting.

Summary:

Some changes can be reversed and some cannot be reversed.
A change may occur by heating a substance or by mixing it with some other.
Some examples of Reversible and Irreversible changes.