Page 1 - 3-Lesson Note-Reversible and Irreversible Changes
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SAI INTERNATIONAL SCHOOL
Class - VI
Subject - Chemistry
Topic – Changes Around Us
Sub-Topic – Reversible and Irreversible Changes
Lesson Note
CLASSIFICATION OF CHANGES:
➢ A substance undergoes a change to form a new substance, only when certain agents
like, heat, light, electricity or force, etc., are applied to it.
➢ If the agent causing the change is removed, then in some cases, the ‘new substance’
undergoes a change in reverse direction to form the ‘original substance’.
➢ Therefore, some changes can be reversed, whereas, other changes cannot be
reversed.
REVERSIBLE CHANGE:
➢ A reversible change is a change that can be
undone or reversed.
➢ A reversible change might change how a
substance looks or feels, but it doesn’t create
new substances.
➢ Temporary changes can be reversed easily to
get the original form of the substance.
➢ E.g., Change of state of matter, Stretching of
spring, Ironing of clothes, rolling of roti from
dough, dissolving salt in water, Expansion and
contraction of metals on heating.
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