This chapter introduces material balances, which apply the law of conservation of mass to accounting for material entering and leaving a chemical engineering system. It discusses open and closed systems, steady-state and unsteady-state systems, and how to perform material balances on single and multiple component systems as well as batch and semi-batch processes. The key concepts covered are the definitions of a system, open vs closed systems, steady-state vs unsteady-state systems, and how to approach material balances for different process types.

1. CHEE 201: Introduction to
Chemical Engineering
Calculations
Dr. Mustafa Alsaady
Textbook: Hammelblau D. M. and Riggs J. B., Basic Principles and
Calculations in Chemical Engineering, 8th Edition Prentice Hall; (2012).
Reference: Ritchard M. Felder, Ronald W. Rousaou, Elementary
Principles of Chemical Processes, 3rd Edition, John Wiley & Sons; (2005)

2. CHAPTER (3):Introduction to Material
Balance
• A material balance is nothing more than the application of the law of
the conservation of mass: "Matter is neither created nor destroyed.
• Material balance
• accounting of material
• normally carried around a system
• Final condition -Initial condition = Sum of inputs -Sum of outputs

3. CHAPTER (3):Introduction to Material
Balance
3.2 Open and Closed Systems.
• A System is a portion or whole of a
process (or a plant) to be analyzed.
• Closed system is a system that does not
have material crossing the system
boundary.
• Open system is a system in which material
crosses the system boundary.

4. CHAPTER (3):Introduction to Material
Balance
3.3 Steady-State and Unsteady-State
Systems.
• Steady-state system is a system for which
all the conditions (e.g., temperature,
pressure, amount of material) remain
constant with time.

5. CHAPTER (3):Introduction to Material
Balance
• Unsteady-state system is a system for
which one or more of the conditions
(e.g., temperature, pressure, amount
of material) of the system vary with
time. Also known as a transient
system.

6. CHAPTER (3):Introduction to Material
Balance

7. CHAPTER (3):Introduction to Material
Balance
3.4 Multiple Component Systems

8. CHAPTER (3):Introduction to Material
Balance
• Material Balances for Batch and Semi-
Batch Processes
• Batch process is a process in which
material is neither added to nor
removed from the process during its
operation.

9. CHAPTER (3):Introduction to Material
Balance
• Semi-batch process is a process in which material enters the
system but product is not removed during operation.