Phase change

Question of the Day May 7, 2012 – Water

Water heats gradually
and boils suddenly.
What is the Meaning of this Statement,
in Your Opinion ? Explain Why…

For me, it is an example of a phase change.

In the specific example, it takes a lot of energy, to heat water, then, at a certain critical threshold (dependent upon pressure), a change of phase is initiated, and water changes from liquid to gas. (As heat is often applied from below, this production of gas produces the phenomenon of boiling, rather than there being a simple sublimation from the surface of the liquid.)

Such “threshold” energy values are important in many ways.
It is also important to note that a lot of energy must be put into the system to initiate the phase change.

Some systems have multiple phase changes possible.
Water under ordinary conditions only has 4 – solid (ice), liquid (water), gas (steam) and as energy is continued to be added, it ceases to be water at all, and becomes a plasma.

So yes to both the answers above, and they are only part of the story.

Sometimes energy induced transitions are much more than simple phase transitions.
Sometimes there is the emergence of whole new orders of properties.
Sometimes catalysts are involved (things that speed the rate of change, but are not themselves changed).
These sorts of transitions may be potentially infinite in type, when dealing with something as complex as a human being, or a collection of human beings.

It is worth noting, that often after such transitions, many of the properties that defined the thing are no longer present, and many new properties have appeared.
Such is the nature, both of phase transitions, and of emergent properties in more complex systems.