A simultaneous thermogravimetric analyzer was used to investigate the gravimetric and energetic behavior of a decomposing sample. Mathematical models were developed from the first law of thermodynamics to accurately quantify the energetic characteristics of a decomposing sample. Models were used to obtain the heat of melting, standard heat of decomposition, heat of decomposition, and heat of gasification. Materials tested in the study included aluminum alloys, chemicals, polymers and composite samples. It was determined that the heat of decomposition of a sample is different than the area difference of the apparent and sensible specific heat curves, an approach that is currently used in the literature. The standard heat of decomposition of samples was proved to be a constant quantity, irrespective of the heating rate or the initial mass of the sample. The standard heat of decomposition estimated from the model was found to be independent of the inert mass in the sample. The model was capable of determining an accurate value of standard heat of decomposition using approximate data of decomposition products. Thus, the standard heat of decomposition is proposed as a unique energetic property of a sample. (C) 2012 Elsevier B.V. All rights reserved.