What is the entropy of isolated system?

Entropy is the measure of the disorder of a system

Explanation:

Entropy is a thermodynamic quantity defined as a criterion to predict the evolution or transformation of thermodynamic systems. In addition, it is used to measure the degree of organization of a system.

In other words: Entropy is the measure of the disorder of a system and is a function of state. That is, it depends only on the state of the system.  

However, in the case of an isolated system in an irreversible process, the value of entropy increases in the course of a process that occurs naturally. While in a reversible process the entropy of the isolated system remains constant.

a.) travels faster in solids because the particles are closer together.

air is a gas water is a liquid

pretty sure it's false