Page 70 - Viva ICSE Science 5 : E-book

Besides carbon dioxide, other gases like oxygen and nitrogen Did You Know!

are also soluble in water. Aquatic animals breathe in oxygen Carbonated drinks
are the aerated drinks
that is dissolved in water, and hence, are able to survive inside
like colas and drinking
the water. soda.

Change of State

We have read in the previous class that matter can change its state from one form to

another. The change of state of a material changes the arrangement of molecules in
that material. Changes can be broadly categorised into two types—physical change
and chemical change.

Physical change

Any change in matter in which no new substance is formed is termed as a physical
change. It may involve a change in the state of matter and it can usually be reversed. It
is not a permanent change.

For example, water (liquid) on cooling becomes ice (solid), and on heating becomes

steam (gas). Here, even though the state of water has changed from liquid to solid and
liquid to gas, it’s still the same. Also, if ice is heated or steam is cooled, we get back water
in its original form.

ACTIVITY TIME

To observe a physical change

You Need:
A beaker, sugar, water, a burner (to be handled by adults only)

What to Do:
• Take a beaker full of water and add two spoonful of sugar
to it.

• Stir the solution until sugar dissolves completely.
• Now ask an elder to heat this solution.

After some time you will observe that the water evaporates and sugar particles are left behind. This
is a physical change because at the end we get back the sugar.

Chemical change

Any change in matter in which one or more new substances are formed is termed as a
chemical change. It is a permanent change and cannot be reversed.

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