Question

1.
2.
To walk through a waterlogged area, you usually shorten the length of your
dress by folding it. Can this change be reversed?
You accidentally dropped your favourite toy and broke it. This is a change you
did not want. Can this change be reversed?
Some changes are listed in the following table. For each change, write in the
blank column, whether the change can be reversed or not.
3.
S. No.
Change
Can be reversed (Yes/No)
1.
The sawing of a piece of wood
2.
The melting of ice candy
3.
Dissolving sugar in water
The cooking of food
5.
The ripening of a mango
6. Souring of milk
4. A drawing sheet changes when you draw a picture on it. Can you reverse this
change?
5. Give examples to explain the difference between changes that can or cannot be
reversed.
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?
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 1

Answer:

The exterior angle is the sum of the interior opposite angles. Since AB=AC, ∠ABC=∠ACB.

Since the sum of angles in a triangle is 180

∘

, ∠BAC=100

∘

Hence, external angle at B = ∠ACB+∠BAC=100

∘

+40

∘

=140

∘ripening of a mango

6. Souring of milk

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

change?

5. Give examples to explain the difference between changes that can or cannot be

reversed.

Answer 2

Answer: 1. Yes, the change can be reversed as you can unfold the cloth again.

2.No, the change is not reversible as the toy broke and you can't bring the pieces together to make the toy again.

3. 1.No

   2.Yes

   3.No

   4.Yes

   5.No

   6.No

4. If the drawing is drawn by pen, it cannot be reversed. If Pencil was used for the drawing, then it can be reversed.

5.  Examples of changes that can be reversed:

   a)Folding Paper

   b)Opening a door

    Examples of changes that cannot be reversed:

   a)Tearing paper

   b)Chopping down a door

6.No, the change in the POP cannot be reversed.

7. No, the cement would harden if it is wet and was dried under the Sun. This change cannot be reversed.

Hope its satisfying

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