For an isolated system, any process that leads to an increase in the disorder of the system will be spontaneous. The following generalizations can help us decide when a chemical reaction leads to an increase in the disorder of the system. Solids have a much more regular structure than liquids. Liquids are therefore more disordered than solids. The particles in a gas are in a state of constant, random motion.
Gases are therefore more disordered than the corresponding liquids.
Any process that increases the number of particles in the system increases the amount of disorder. Click here to check your answer to Practice Problem 2. The sign of H for a chemical reaction affects the direction in which the reaction occurs. Spontaneous reactions often, but not always, give off energy. The sign of S for a reaction can also determine the direction of the reaction.