Describe what happens to particles as they go through a phase change and energy is added

Solid-When a solid is heated the particles gain energy and start to vibrate faster and faster. Initially the structure is gradually weakened which has the effect of expanding the solid. Further heating provides more energy until the particles start to break free of the structure. Although the particles are still loosely connected they are able to move around. At this point the solid is melting to form a liquid.

Liquid-As the liquid gets warmer more particles have sufficient energy to escape from the liquid. Eventually even particles in the middle of the liquid form bubbles of gas in the liquid. At this point the liquid is boiling and turning to gas. The particles in the gas are the same as they were in the liquid they just have more energy. At normal atmospheric pressure all materials have a specific temperature at which boiling occurs. This is called the "boiling point" or boiling temperature.

Description of Phase ChangeTerm for Phase ChangeHeat Movement During Phase Change

Solid to liquidMeltingHeat goes into the solid as it melts.

Liquid to solidFreezingHeat leaves the liquid as it freezes.

Liquid to gasVaporization, which includes boiling and evaporation. Heat  goes into the liquid as it vaporizes.

Gas to liquidCondensationHeat leaves the gas as it condenses.

Solid to gasSublimationHeat goes into the solid as it sublimates.

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.