False!  The order of the system is determined by the number of first order ordinary differential equations solved to determine the output variable from the input variable.  In a single stirred tank, we might need one balance (e.g., a component), two balances (e.g., a component and energy) or many balances (overall material, energy, and several component). 

Key lesson:  We cannot determine the order of a system by observing the equipment.  We must define the system, specify the input and output variables and formulate the model.