Page 71 - Science Class 06

Contrac on in Solids Contrac on in Liquids Contrac on in Gases

If we hold a very hot glass We observed that water If an inflated balloon is ed
tumbler under cold water, expanded on hea ng. Can at the mouth of a bo le
it cracks. This is because the you say what will happen if and the bo le is placed in

outer surface of the glass the water is allowed to cool ice-cold water, what will
comes in direct contact with down and then poured back happen? The balloon will
cold water and contracts into the glass? Would it s ll shrink in size, as the air
more as compared to the overflow? No. This is because inside the balloon contracts
inner surface. of contrac on. on cooling.

MIXING AS A WAY OF CHANGING THINGS Let us perform an ac vity to know further
about solubility of different solids in liquids:
Change can also be brought about in a
substance by mixing it with another.

For example : Mixing solid with a liquid:
Take five glasses of the same size. Fill each
When we mix a spoon of salt (solid) with of the glasses with water.
water (liquid), we are actually changing the

state of salt.
Actually, the salt has changed from its solid

state to a liquid state. I II III IV V
It means that, the salt and water are so well
mixed with each other the every spoonful
To see the solubility of different solids in liquids.
of the mixture will taste like salt and also be
wet like water. Number the glasses, c, II, III, IV and V. Use
five teaspoons (of the same size) to
A solu on has the measure out the following substances:
proper es of all the salt, sugar, sand, mud and baking soda.
things that are mixed to
form it. Add salt to glass I, sugar to glass II, sand to
glass III, mud to glass IV and baking soda
to glass V.
Dissolving salt in water to form a salt solu on.

Science-6 71