Heat Capacities: Summary

The answers to the ConcepTests are given below and will open in a separate window. 
Key points from this module:
  • Heat capacities increase with temperature.
  • For ideal gases, internal energy (U) and enthalpy (H) depend only on temperature, not pressure.
  • For liquids and solids, U and H depend on temperature, but do not change significantly with pressure.
  • Enthalpy changes with temperature for ideal gas mixtures can be calculated as the sum of ΔH values of the pure components.
  • If heat of mixing is zero for a liquid mixture, enthalpy changes with temperature are the sum of ΔH values of the pure components.
  • The NIST webbook (https://webbook.nist.gov/) is a good source for heat capacity data.
  • This screencast demonstrates how to use the NIST WebBook to calculate enthalpy, and an example is shown in this spreadsheet.
From studying this module, you should now be able to:
  • Calculate the final temperature when a given amount of heat is added to a gas, liquid, or solid.
  • Calculate the amount of heat needed to raise a substance to a given temperature.
  • Calculate enthalpy changes when more than one temperature-dependent heat capacity equation is required to cover the temperature range.

Related modules: Adiabatic Flame Temperature, Heats of Reaction

Prepared by John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder