Page 32 - ICSE Chemistry 8

Changes that occur very quickly are called fast changes. For example, burning of paper and breaking of
glass are fast changes.

after
a few hours

milk + starter culture curd
curdling of milk burning of paper
Fig. 2.4: Slow and fast changes

Activity 2.2

Aim: To iden fy the changes

Write Yes if the change is slow and No if it is not.
Change Slow
Bursting of crackers

Change of seasons
Germination of seeds

Lightning
Bursting of an in lated balloon
Curdling of milk

Cutting of paper
Baking of cake

Closing the door
Growth of a child

NATURAL AND MAN-MADE CHANGES

Changes that occur naturally on their own, i.e., north pole
without any human eff ort and are beyond human
control are called natural changes. For example,
rota on and revolu on of the earth, change of day
into night and forma on of coal and petroleum
occur naturally, and hence are natural changes.
Changes that occur due to human eff ort or ac vity
and are brought about ar fi cially are called man-
made changes. For example, air pollu on, cooking south pole
of food, and manufacturing of clothes and furniture rotation of the earth cooking of food
are man-made changes. Fig. 2.5: Natural and man-made changes

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