Page 66 - Viva ICSE Science 5 : E-book

6

States of Matter

We have learnt in previous classes that anything
KEY CONCEPTS
that has mass and occupies space is called matter.
All objects are made of matter. Matter consists • Solid • Liquid • Gas
of tiny particles known as molecules. Molecules • Solubility of substances in water

are so small that they cannot be seen with naked • Change of state
• Separation of liquids from solids
eyes. These molecules are further composed of
• Air
very small particles called atoms. Atoms are the

smallest unit of matter, and therefore, also known
as the ‘building blocks of matter’.

On the basis of arrangement of molecules in a substance, we can categorise substances

into solids, liquids and gases. Let’s study about them in detail.

Solid

Solids have fi xed shape and size. This is because the molecules
in a solid are tightly packed. There is a strong force of attraction
between the molecules of a solid. Because of this reason a solid

has the following properties.

(i) The solids have fi xed shape.
(ii) They have a fi xed volume. They have a size. Arrangement of
molecules in solids
(iii) They occupy space.

(iv) Solids cannot fl ow.

However, the shape of some solids can be changed by applying force.

The molecules in a solid are arranged in a defi nite pattern, e.g., sugar crystals and

diamonds. When a solid is broken into pieces, it does not fl ow like liquid. Each piece still
holds the defi nite pattern in which its molecules are arranged.

Molecules in some solids are not arranged in defi nite pattern, e.g., rubber, glass and
plastic.

52