Science Buddies: "Ask an Expert"

Is it possible for matter to change state without a temperature increase or decrease? Such as to where, on the molecular level, the bonds holding the particles together are broken and the matter changes state. I'm sure this wouldn't happen naturally, but is it possible to scientifically induce this kind of change?

Is it possible for matter to change state without a temperature increase or decrease?

This is a great question that isn't easy to answer.

With H2O (water), there is a known tripple point temperature where it can exist as ice (solid), liquid (water), and gas (water vapor). Look up "tripple point of water" to find out more.

There is something called an "equillibrium" where the amount of matter in each state is constant but the state of any given molecule can be changing state. It takes a certain amount of energy (Heat of fusion) to go between solid and liquid and (Heat of vaporization) to go between liquid and gas; however, an equal and opposit amount of energy transfer occurs for the opposite direction. This means that the heat released by freezing liquid can equalize with the heat consumed by thawing the solid. The same is true for the balance of heat consumed to vaporize a liquid molecule and the heat released by condensing a liquid molecule.

Reaching an equilibrium is an extremely rare possibility in nature, so does it happen outside of carefully constructed experimental conditions? Great unanswerable question.

You might also be interested to read up on "phase diagrams" which show how you can cause a change in state with variable pressure and constant temperature.
http://en.wikipedia.org/wiki/Image:Phase-diag2.svg
Also check out "supercooled water", which is an example of how nucleating agents (dust, seed crystals, etc) can affect changes of state https://www.sciencebuddies.org/science- ... p033.shtml
"Superheating" is another relevant phenomenon of a phase change initiated by something other than change in temperature.
http://en.wikipedia.org/wiki/Superheating
These are some examples of naturally occurring phase changes that are not a direct result of temperature change.
Regards,
Chris