Page 67 - Science Class 06
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Irreversible Changes
A change that becomes permanent in
nature is an irreversible change. For
instance, when we burn paper it turns to
ash and cannot be turned back to paper.
Therefore, this is permanent.
Burning of paper and ripening a fruit
Temporary changes are irreversible changes.
1. Give two examples of each periodic and 1. To walk through a waterlogged area, you
non-periodic changes. usually shorten the length of your dress
2. Why burning of paper is called a by folding it. Can this change be reversed?
permanent change? 2. You accidentally dropped your favourite
3. Conver ng water into ice is a permanent toy and broke it. This is a change you did
or temporary change? Why? not want. Can this change be reversed?
REVERSIBILITY TYPES OF REACTIONS
In view of reversibility, a change may be In view of the type of reac on, a change
worth reversing or not. So, in terms of this may be only physical, i.e., in form, tempo-
factor, changes are of two types—reversible rary and reversible without forming a new
substance. It may also be permanent,
and irreversible.
irreversible because of forming a new
Reversible Changes
substance with new proper es as a result of
Those changes which may be reversed are a chemical ac on. So, in terms of the type
reversible changes. For instance, changing of reac on, changes can be of two types—
water to ice and vice versa will be categori- physical and chemical.
sed under this. Physical Changes
Changes in the physical proper es of a
substance are known as physical changes.
Physical proper es of a substance include
Freezing of water into ice is a reversible change colour, size, shape, state, temperature,
because it can be converted into water again. odour, appearance, texture and many more.
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