Page 126 - Active Science 5 Ebook and Activity

Just as alphabets are building blocks of English, atoms are the building blocks of
matter. In other words, atoms are the smallest unit of which matter is made. Atoms are

extremely small in size which can only be seen with the help of a microscope. Everything
around us is made up of atoms but we cannot see these with our naked eyes.

Molecules

Atoms combine together to form larger units called molecules.
Atoms and molecules are constantly moving, i.e., they are always O O

in motion. Different molecules together in a large number make up
different substances. For example, water is formed by two atoms of O 2
hydrogen and a single atom of oxygen. Also, an oxygen molecule is Oxygen molecule
made up of two atoms of oxygen atom.
H H
There are three states of matter – solid, liquid and gas. Sometimes,

the same matter can exist in all the three states of matter. For
example, water exists in all the three states – in solid state as ice, H O
2
in liquid state as water and in gaseous state as water vapour. Water molecule

Intermolecular Space

Intermolecular space is the space between two molecules. If we add a spoon of salt
into water, it dissolves as it occupies the intermolecular space of water. Study the
arrangement of molecules in different states of matter.

Solid Liquid Gas

Molecules are tightly packed. Molecules have space and are Molecules are very loosely
loosely packed. packed.

Solids have a definite shape Liquid has no definite shape Gases neither have definite
and volume. but have a definite volume. shape nor volume.
The molecules attract each Molecules attract each other The force of attraction among
other with great force. with less force. molecules is the least.
Intermolecular space is Intermolecular space is more Intermolecular space is very
almost negligible. than in solids. large.
The molecular arrangement The molecular arrangement Gases spread in all directions.

makes the solid hard and makes the liquid free flowing.
rigid.

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