Page 59 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

We convert solid into liquid and subsequently liquid into gas by
supplying heat. If so, won't the particles of gas have higher energy
than in the other two states?
The particles of solid are very close to each other. Their freedom
of movement is limited.

In the liquid state, particles are relatively farther apart and have
more freedom of movement than in the solid state.
In the gaseous state, particles remain far away from one another.
Their freedom of movement is very high.

The difference in temperature causes the change of state.
In all states, when heat is provided, the energy and movement of
particles increase, while attraction among particles decreases.
Some substances, when heated, change directly into gas without
forming liquid. This phenomenon is sublimation.
When the vapours of these

Liquid substances are cooled, they change
Liquefaction Vapourisation Naphthalene and iodine are
directly into the solid form.
Solidification
examples for such substances.
Condensation
Solidification Examine the given picture.
Solid Gas Analyse Table 4.3 given below and
Sublimation
write down the changes during the
transformation of states.
When solid When liquid When gas When solid
changes into changes into changes into changes into
liquid gas liquid gas
Movement of particles
Distance between particles

Attraction between particles
Energy of particles
Table 4.3

Diffusion of substances in different states

Let's look at another property of matter.
Iodine is a substance that is easily converted into gas on heating.
Heat a few crystals of iodine in a watch glass. Collect the vapour

Basic Science VIII
58 58 Basic Science VIII