The air bags that provide protection in automobiles in the event of an accident expand because of a rapid chemical reaction. From the viewpoint of the chemical reactants as the system, what do you expect for the signs of q and w in this process?

Key Concepts

Enthalpy (q)

Enthalpy, represented as 'q', refers to the heat content of a system at constant pressure. In the context of the airbag deployment, the rapid chemical reaction generates heat, indicating that the system is releasing energy to the surroundings. Therefore, for the reactants, the sign of q is expected to be negative, as the system loses heat during the exothermic reaction.

Work (w)

Work, denoted as 'w', is the energy transferred when a force is applied over a distance. In the case of an airbag, the rapid expansion of gas against the atmospheric pressure represents work done by the system. Since the system is expanding, the work done by the system is considered positive, leading to a positive sign for w.

First Law of Thermodynamics

The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. In the airbag scenario, the chemical energy from the reactants is converted into thermal energy (heat) and mechanical energy (work) as the gas expands. This principle helps in understanding the relationship between q, w, and the internal energy change of the system.