If matter is not able to pass across the boundary, then the system is said to be closed otherwise, it is open. The boundary must be clearly defined, so one can clearly say whether a given part of the world is in the system or in the surroundings. Everything outside of the boundary is considered the surroundings, which would include the container itself. For example, if the system is one mole of a gas in a container, then the boundary is simply the inner wall of the container itself. The system and surroundings are separated by a boundary. Everything that is not a part of the system constitutes its surroundings. In order to avoid confusion, scientists discuss thermodynamic values in reference to a system and its surroundings. entropyA thermodynamic property that is the measure of a system’s thermal energy per unit of temperature that is unavailable for doing useful work.absolute zeroThe lowest temperature that is theoretically possible.The third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero.The second law of thermodynamics states that the entropy of any isolated system always increases.The first law, also known as Law of Conservation of Energy, states that energy cannot be created or destroyed in an isolated system.