Process Calculations
Syllabus Unit: Process Calculations and Thermodynamics
Why it matters
Chapter overview
Explore the physical forces, chemical structures, and thermodynamic equations behind Process Calculations. An interactive laboratory simulator mapping variables to physical reactions.
1Steady & Unsteady State Mass and Energy Balances
The law, the derivation, and the variable intuition behind Steady & Unsteady State Mass and Energy Balances.
Learning Objectives
- State the governing law or principle behind Steady & Unsteady State Mass and Energy Balances.
- Rebuild the key formula for Steady & Unsteady State Mass and Energy Balances from first principles.
- Predict the outcome of Steady & Unsteady State Mass and Energy Balances when one variable doubles or flips.
- Solve one Process Calculations numerical on Steady & Unsteady State Mass and Energy Balances in SI units.
Key Terms
**Steady & Unsteady State Mass and Energy Balances** sits inside *Process Calculations* (Process Calculations and Thermodynamics in GATE Chemical Engineering Syllabus). Every physics chapter rests on a law or principle — state that law cleanly first and the formulas that follow become consequences, not facts to memorise.
The governing law
Steady & Unsteady State Mass and Energy Balances describes how a physical system responds when its inputs change. The law tells you which quantities are conserved and which are transformed, and — just as importantly — where the law stops holding.
- The conserved quantities involved (energy, momentum, charge).
- The cause-effect relation at the centre of Steady & Unsteady State Mass and Energy Balances.
- The special cases: low speed, small angles, ideal conditions.
- The limits where the approximation breaks down.
Systematic derivation
Learn Steady & Unsteady State Mass and Energy Balances by rebuilding it — derive, don't memorise:
- Start from the fundamental law of the topic.
- Draw the free-body or system diagram.
- Apply the law along each relevant direction.
- Simplify algebraically to the final relation.
Variable thinking
Mentally run the simulation before reading the options — what happens if you double the temperature or flip the field direction? Predicting the trend of Steady & Unsteady State Mass and Energy Balances first catches most wrong choices instantly.
- Temperature up → kinetic energy and velocity up.
- Force applied → acceleration or deflection changes.
- Resistance or friction → energy drains from the system.
- Field direction flipped → the effect reverses sign.