Page 95 - Innovator's Science-8

happens because the particles of the fragrance move throughout the
room. This process is called diffusion . The tiny fragrance particles float in

the air and are constantly moved around by the invisible air particles
bumping into them. Since gas particles move freely in all directions, the
fragrance spreads quickly and fills the entire room. This is why the smell of
the incense is felt everywhere, not just near where it is burned.

Matter is made up of very small particles that are held together by forces of
attraction called interparticle forces. These forces vary in strength

depending on the state of matter and the distance between the particles.
When particles are close together, like in solids, the attractive forces are
very strong, keeping the particles tightly packed and only allowing them to
vibrate in place. In liquids, the particles are a bit farther apart, so the forces
of attraction are weaker, allowing particles to move around but still stay

close. In gases, the particles are far apart and move freely, so the forces of
attraction are very weak or negligible. The thermal energy or heat energy of
the particles affects how much they move and the distance between them,
which in turn changes the strength of these forces and therefore the

physical state of the matter. For example, heating solid increases the
particles' energy so much that they can overcome the strong attractive
forces, allowing the solid to melt into a liquid where particles can move
more freely. Heating further can turn a liquid into gas by providing enough

energy for particles to break almost all attractions and move independently.
Know Your Scientist
John Dalton (1766-1844, England)
More than two thousand years after Acharya Kanad, the English scientist John Dalton presented his Atomic
Theory in 1808, which gave a scientific explanation for the nature of matter. Dalton proposed that:
• All matter is made up of small particles called atoms.
• Atoms cannot be divided, created, or destroyed.
• Atoms of the same element are identical, while atoms of different elements differ in mass and properties.
• Atoms combine in simple whole-number ratios to form compounds.
Dalton's theory helped scientists understand how matter behaves during chemical reactions. It provided a
solid experimental foundation for the ancient idea that matter is made up of tiny indivisible particles -
something Acharya Kanad had described long ago in philosophical terms.

Grasp-Up

Ma er: Anything that has mass and occupies space
Par cles: Very small parts that make up ma er
Interpar cle space: The empty space between par cles of ma er
Interpar cle a rac on: The force that holds par cles together
Diffusion: The process by which par cles of two substances mix on the own

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Science-8