Heat Change and Phase Change Formulas and Some Constants for Water

General Chemistry Index

Where are we going with this? This page will assist in developing the ability to perform calculations involving heat flow, temperature changes, and phase changes by using known values of specific heat, phase change constants, or both.

Heat Change and Phase Change Formulas and Some Constants for Water

These equations apply to heat and phase changes in general.

Temperature Change Formula:

Q = mc∆T

Phase Change, Solid <--> Liquid

Q=m∆Hf

Phase Change, Liquid <--> Gas

Q=m∆Hv

Many questions involve water. Here are the constants related to water.

Specific Heats for H2O

Solid (Ice) = 2.09 J/g • °C

Liquid (Water) = 4.128 J/g • °C

Gas (Steam) = 1.996 J/g • °C

Phase Change Constants for H2O 

Solid <--> Liquid — m∆Hf  = 334 J/g 

Liquid <--> Gas — m∆Hf  = 2257 J/g