4.1 - Open Systems

Important Features of an Energy Bar Chart:

Before making an Energy Bar Chart, be sure to define your system and make a System Schema and State Diagrams if needed. Remember, the System Schema diagram identifies the objects that interact during a process or change.  State Diagrams represent the positions or configurations of objects in your system at the instants that you choose to represent your system with Energy Bar Charts (at the very least you will represent initial and final states, but sometimes intermediate states as well). Next, an Energy Bar Chart will help us track changes in how the System stores and transfers energy during the process or change.

Each “bar” or “block” in the Initial graph or the Final graph of an Energy Bar Chart represents how the System is storing energy.  The circle in the middle is used to represent the system.  The circle in the middle is also used to show Energy Flow.  We can use ‘quantified arrows’ (like the bars on the bar chart) that point into or out of the System circle to represent the amount of energy being transferred into or out of the system.  If there are no transfers of energy into or out of the system, no arrow would point into or out of the system. This means the system was chosen to include all relevant objects, and the analysis is simplified: energy is conserved!  In this instance, the initial and final bar graphs must have an equal number of “blocks” or “bars” distributed among the different modes of energy storage.