For a lengthy time researchers knew about theinvariance of temperature during 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 must look in ~ the phasechange indigenous a microscopic allude of view, in otherwords, we require to explain the observed behavior interms of the activity of the atoms and moleculesthat type the substance.

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As one example,let"s talk about boiling a pure liquid, however thesame reasoning can describe freezing/melting. Whenyou start heating a mass of liquid, the heatabsorbed by the system rises the kineticenergy of the molecules, they will certainly movefaster.

This power increase is what we have the right to observe together anincrease in the temperature. More heat in andtemperature will go greater and higher and higher,until over there comes a moment when the molecules haveacquired enough energy to get over the pressures thatkeep them with each other in the liquid phase and theystart to escape native every part of the liquid intothe gas phase, that way the liquid boils. (Thekey allude here is from EVERY part OF THE LIQUIDPHASE, because normally during the heater up,molecules will certainly be escaping from the surface intothe gas phase every the time ). When this happens,the molecules that escape to the gas step takeaway some energy from the liquid phase, and also sincewe continue heating they will proceed to escape.

The result we had actually observed before (increase oftemperature together we give an ext heat to the system) isnot feasible anymore, since the vaporizingmolecules space taking far the energy that is beingsupplied to the system. The means, boiling occursat continuous temperature till all the fluid isgone, in i beg your pardon case, if we proceed to heat up,then we will boost the temperature the the gasformed.

All this procedure has developed atconstant pressure, as once we execute ourexperiments in an open container.

Answer 2:

When a problem is provided energy in the kind ofheat, it"s temperature increases. The extent oftemperature rise is established by the heatcapacity of the substance. The larger the heatcapacity the a substance, the much more energy isrequired come raise that is temperature.

When asubstance undergoes a first ORDER step change,its temperature remains consistent as long as thephase readjust remains incomplete. once iceat -10 degrees C is heated, its temperature risesuntil the reaches 0 degrees C. At the temperature,it beginning melting and solid water is convert toliquid water. Throughout this time, all the heatenergy listed to the system is offered UP in theprocess of convert solid come the liquid. Onlywhen all the heavy is converted, is the warm usedto advanced the temperature that theliquid.

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

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This is the renowned "divergence"of theheat capacity during a an initial order phasetransition.

There are particular phasetransitions whereby the heat capacity walk notbecome infinitely large, such as the procedure of anon-magnetic substance becoming a magneticsubstance (when cooled listed below the so-calledCurie temperature).

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