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When we consider the term 'exothermic', we are talking about a process that releases energy in the form of heat. The chemical reaction that inflates airbags is a perfect example of this. Imagine the rapid decomposition of sodium azide within the airbag's mechanism.

This safety feature relies on a precise chemical formula: \[2 NaN_3(s) \rightarrow 2 Na(s) + 3 N_2(g) + \text{heat}\].

Whenever a sodium azide molecule breaks apart, it releases heat energy into the surrounding area. This heat is not just a byproduct; it is a fundamental aspect of how the airbag works, propelling the inflation process and ultimately cushioning the car's occupants more effectively. This is what makes it an exothermic reaction – it is an essential component that contributes to the swift reaction that airbag deployment requires.

The concept of enthalpy change is essentially a way of expressing the heat change at constant pressure within a chemical system. In the case of the airbag inflation, we see this in action as the enthalpy changes when sodium azide decomposes.

Enthalpy, symbolized as H, changes as exothermic reactions release heat, leading to a drop in the system's enthalpy. Mathematically, this is shown by a negative sign for the change in enthalpy (\( \Delta H < 0 \)). This means in the context of airbags, the energetic output is a significant factor, and it's measured as part of the chemical thermodynamics of the reaction.

Delving further into chemical thermodynamics, we understand that it pertains to the transfer of heat and work in chemical processes. The activation of an airbag showcases the interplay between various forms of energy during a chemical reaction.

As highlighted by the signs of \(q\) (heat) and \(w\) (work), chemical thermodynamics involves understanding how energy is moved or transformed. In an airbag, the initial chemical potential energy stored in the sodium azide is suddenly released as kinetic energy of nitrogen gas molecules and thermal energy (heat), showcasing an exothermic thermodynamic process.

Gas expansion in the context of airbags refers to the rapid increase in volume as a result of chemical reactions producing gas. Specifically, the nitrogen gas produced during the decomposition of sodium azide fills the airbag, expanding it almost instantaneously.

The production of gas is a physical manifestation of work (\(w\)) being done, where the force of the expanding gases pushes against the confines of the airbag and also on the surrounding environment. The rapidness of this expansion is crucial for protection during a collision, and it underscores the vital relationship between chemical reactions and physical outcomes in practical applications like vehicle safety.