The little children stand squished together
in a tight enclosed space
Straight
uniform
But...
squirmy
Unable to be completely still

A solid phase

Then, they start to squirm some more
as their boredom takes over
wriggle
shake
some start coming off
the tightly knit shape
More and more
lose
and open spaces
Until its a shapeless mass of kids
Each with ample space

Liquid phase

Then they get tired of standing around
Some start playing tag
Running about
leaving
wandering
Dispersed
Until finally,
...
The once tightly knit
figure
is simply
a few random kids
zooming around
here and there

Gas phase