Out of sublimation, condensation, evaporation, boiling, melting & freezing: classify these changes of state into two groups-heat taken in &..heat given out by the particles.

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ndnordic's profile pic

ndnordic | High School Teacher | (Level 2) Associate Educator

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The underlying concept behind changes of state is kinetic molecular theory - the idea that all particles in substances are constantly in motion.

Two factors determine the physical state of any substance:  the relative attraction between particles and the velocity of the particles.

A change of state where heat is added is called an endothermic phase change.  Endo meaning entering or going in, and therm referring to heat.  When heat is added to a substance the velocity of the particles (their kinetic energy) also increases.  As their velocity increases, the particles move further apart, and the attraction between particles decreases.  This happens during melting, boiling, and sublimation (the direct change from a solid to a gas).

A change of state where heat is removed is called an exothermic phase change. Exo meaning leaving or going out, and therm again referring to heat..  When heat is removed, the velocity of the particles decreases, they get closer together, and the attraction between the particles becomes more important and more likely.  Exothermic phase changes are solidification, condensation, and deposition (direct change from a gas to a solid)

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krishna-agrawala's profile pic

krishna-agrawala | College Teacher | (Level 3) Valedictorian

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Sublimation is the process of a material in solid state changing directly in to gaseous state without going through intermediate liquid stage. In this process the particle of material sublimating absorb latent heat.

Condensation is the process of material in gaseous stage passing in to liquid stage when latent heat of evaporation is removed from the material in vapour or gaseous form.

Evaporation is the process opposite of condensation. In this process a material in liquid form changes its state in gaseous form. In this process the material absorbs the latent heat of evaporation.

Boiling refers to the agitation in a mass of liquid caused by liquid particle below the surface of the liquid changing from liquid to gaseous state. Thus the process of boiling is accompanied by rapid evaporation, which involves absorption of latent heat of evaporation by the particles changing state from liquid to gaseous.

Process of melting involves material in solid state changing its form from solid to liquid. In this process the material absorbs latent heat of fusion.

Process of freezing, also called solidification, is opposite of melting. It is accompanied by the material being frozen to solidifying releasing heat of fusion.

mohamedvakkayil's profile pic

mohamedvakkayil | Student, Undergraduate | (Level 1) eNoter

Posted on

hai friend,

from your points, melting, boiling and sublimation are the process done when heat taken in for transition of state of matter from solid to liquid, liquid to gas and solid to gas respectively, also evaporation comes in this section.

Condensation and freezing are done when heat gone out.

best regards