Relevance of Phase Changes

[Alice Chang 2H]

What is the relevance of knowing phase changes? Like, how are they used in calculations?

[J Medina 2I]

If you are calculating the change in enthalpy of a substance and that substance changes phases then it is important to add the energy required by the phase change in order to get an accurate calculation for ΔH.

[William Francis 2E]

You need to take phase changes into account when calculating change of enthalpy in a reaction. The calculations we use assume that all the reactants and products are gases.

[Emily Burghart 1k]

In many of the problems covered in thermo, you have to calculate the energies expelled/absorbed for each part of the phase change, and then add those up to find your enthalpy, .

[Sydney Pell 2E]

When you are calculating the enthalpy of a reaction, sometimes the reactants or products will be in the liquid form. Since predetermined enthalpy values of elements are usually given in the gas phase, you must add/subtract the enthalpies of the phase changes to these values to determine what they are in a different state so that the overall enthalpy change of the reaction can be calculated.

[ABombino_2J]

When calculating the enthalpy change you need to add the enthalpy as a result of change in temperature as well as the enthalpy that comes from a phase change.

[Janet Nguy 2C]

Since the enthalpy value changes when a substances changes phases, it is necessary to calculate separately the phase change enthalpy and add it to the same-phase reaction enthalpy.

[Trent Yamamoto 2J]

A phase change would mean that you would have to add the energy required for that phase change in order to calculate the overall enthalpy

[Alondra]

This is important when calculating enthalpy because energy is used for a phase change as well as temperature.

[Megan Kirschner]

I think also phase change helps orient what values will be positive and negative. You need to take phase changes into account when calculating the change of enthalpy in a reaction (the calculations we use assume that all the reactants and products are gases).