For a long time researchers knew about theinvariance of temperature throughout phase changes,but this phenomenon can not be described in termsof the typically observable variables, that is, themacroscopic or thermodynamic variables. Tounderstand the WHY we should look at the phasechange indigenous a microscopic allude of view, in otherwords, we need to explain the observed actions interms that the movement of the atoms and also moleculesthat type the substance.

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As an example,let"s talk about boiling a pure liquid, yet thesame thinking can explain freezing/melting. Whenyou start heating a fixed of liquid, the heatabsorbed by the system boosts the kineticenergy that the molecules, they will certainly movefaster.

This energy increase is what we can observe as anincrease in the temperature. Much more heat in andtemperature will go higher and higher and higher,until there comes a moment when the molecules haveacquired enough energy to conquer the pressures thatkeep them together in the fluid phase and also theystart come escape from every component of the liquid intothe gas phase, that means the liquid boils. (Thekey allude here is native EVERY part OF THE LIQUIDPHASE, since normally throughout the heating up,molecules will certainly be escaping indigenous the surface ar intothe gas phase all the time ). Once this happens,the molecules that escape to the gas step takeaway some energy from the fluid phase, and also sincewe proceed heating they will continue to escape.

The impact we had observed before (increase oftemperature as we give an ext heat come the system) isnot possible anymore, because the vaporizingmolecules room taking far the power that is beingsupplied to the system. That means, boiling occursat consistent temperature till all the fluid isgone, in which case, if we continue to warm up,then us will increase the temperature that the gasformed.

All this procedure has occurred atconstant pressure, as once we carry out ourexperiments in an open container.

Answer 2:

When a substance is noted energy in the type ofheat, it"s temperature increases. The extent oftemperature increase is identified by the heatcapacity of the substance. The bigger the heatcapacity the a substance, the an ext energy isrequired to raise that temperature.

When asubstance experience a first ORDER phase change,its temperature remains consistent as long as thephase adjust remains incomplete. as soon as iceat -10 degrees C is heated, the temperature risesuntil that reaches 0 levels C. At that temperature,it start melting and solid water is converted toliquid water. Throughout this time, all the heatenergy listed to the mechanism is offered UP in theprocess of convert solid come the liquid. Onlywhen every the heavy is converted, is the heat usedto progressive the temperature the theliquid.

This is what results in the flatpart that the freezing/melting ofcondensation/boiling curve. In this flatregion, the warmth capacity that the substance isinfinite.

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This is the renowned "divergence"of theheat capacity during a very first order phasetransition.

There are specific phasetransitions wherein the warm capacity does notbecome infinitely large, such together the procedure of anon-magnetic substance coming to be a magneticsubstance (when cooled listed below the so-calledCurie temperature).