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Secondary I • 1yr.

At the molecular level, what explains the phase changes?

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Explanations (1)

  • Explanation from Alloprof

    Explanation from Alloprof

    This Explanation was submitted by a member of the Alloprof team.

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    Team Alloprof • 1yr.

    Thank you for your question!

    Phase changes take place with variations in temperature. Thus, their molecular explanation depends a lot on this temperature variation:

    • During transitions which take place due to an increase in temperature, that is to say, fusion, vaporization and sublimation, the molecules absorb a lot of energy and start to move a lot more. This has the effect of reducing the pressure and also the strength of the bonds between the molecules. Thus, substances tend to change from solid, to liquid, to gas, the pressure and strength of the bonds decreases in this order.

    • During transitions that take place due to a decrease in temperature, that is, liquid condensation, solidification and solid condensation, molecules give off a lot of energy and start to move much less . This has the effect of increasing the pressure and also the strength of the bonds between molecules. Thus, substances tend to change from gas, to liquid, to solid, the pressure and strength of the bonds increases in this order.

    Do not hesitate if you have other questions!