⚗️ Introduction to Chemical Engineering

What you’ll learn

1. The Beaker and the RefineryUnderstand chemical engineering as the discipline of scale: why a reaction that works in a flask can be impossible in a tank.A chemist's job ends when a reaction works; a chemical engineer's begins there, because making the same reaction happen continuously, by the tonne, safely and profitably, is a fundamentally different problem. The gap between the beaker and the plant is not one of size but of kind — at scale, heat, mixing, separation and time behave in ways that a flask on a bench never reveals.
2. The Unit OperationGrasp the organising idea of chemical engineering: that any process, in any industry, is built from a small reusable alphabet of physical operations.The founding insight of the discipline is that industrial processes differ in their chemistry but share their physical steps — distillation is distillation whether you are separating whiskey or gasoline. Recognising a small vocabulary of unit operations that can be studied once and applied everywhere is what turned a collection of trades into a profession, and it is why a chemical engineer can read a plant they have never seen.
3. The Accountant's LawApply a material balance: account for every atom entering and leaving a process, and use the balance to deduce quantities you never measured.A material balance states that what goes in must come out or accumulate — mass is conserved, so a process cannot lose track of atoms. Drawing a boundary around a process and accounting rigorously across it is the chemical engineer's fundamental move, and its power is deductive: balances routinely reveal quantities that were never measured, and a balance that fails to close is evidence that something real is unaccounted for.
4. Heat Is a Material TooApply the energy balance and recognise heat as the dominant operating cost and the dominant design constraint.Energy obeys the same accounting law as mass — in equals out plus accumulation — but heat is far harder to contain than matter, which makes it the expensive stream. Reactions release or absorb energy that must be removed or supplied, phase changes carry enormous latent heat, and much of a plant's equipment and running cost exists to move heat rather than to make anything.
5. The Square-Cube TrapUnderstand why scale-up is fundamentally hard: volume grows faster than surface area, so a bigger reactor makes more heat than it can shed.Making a reactor ten times larger in each dimension multiplies its volume — and the heat its contents generate — by a thousand, while its surface area, and so its ability to shed heat, grows only a hundredfold. The cooling capacity per unit of reacting material therefore falls by a factor of ten purely from getting bigger, which is why a reaction that is docile in a flask can run away in a tank and why engineers redesign geometry rather than simply scaling it.
6. Separation Is the Real WorkUnderstand why separating products from mixtures dominates a plant, and how a distillation column exploits repeated partial vaporisation.Reactions almost never go to completion or produce only the desired product, so the output is a mixture and most of a plant exists to un-mix it. Distillation works because vapour above a boiling mixture is richer in the more volatile component, and stacking that small enrichment dozens of times up a column compounds it into a sharp separation — unless an azeotrope, like ethanol–water at 95.63% by mass, makes the vapour and liquid identical and stops the mechanism dead.
7. Batch, or Never Stop?Compare batch and continuous reactors, and understand residence time as the reactor designer's central variable.A batch reactor fills, reacts and empties like cooking a pot, giving flexibility and easy changeover at the cost of downtime and batch-to-batch variation, while a continuous reactor never stops and trades flexibility for steady, cheap, uniform output at enormous scale. The variable connecting them is residence time — how long material spends inside — which in a continuous reactor is set by the ratio of volume to flow rate, making the reactor's size a direct statement about the chemistry's speed.
8. A Plant Is a LoopRecognise recycle and control as the features that make a plant an interconnected system rather than a sequence of steps.Because reactors rarely convert all their feed, plants recycle unreacted material back to the front — which turns a linear sequence into a loop and makes every unit depend on every other, including the possibility that impurities accumulate until a purge is required. Combined with feedback control, this means a plant behaves as a coupled system where a local change propagates all the way round, and it is why chemical engineers think in flowsheets rather than steps.

Questions this course answers

Grounded in trusted sources

• R.M. Felder & R.W. Rousseau, 'Elementary Principles of Chemical Processes', 4th ed.
• W.L. McCabe, J.C. Smith & P. Harriott, 'Unit Operations of Chemical Engineering', 7th ed.
• O. Levenspiel, 'Chemical Reaction Engineering', 3rd ed.
• 'Perry's Chemical Engineers' Handbook', 9th ed.
• T. Kletz, 'Process Plants: A Handbook for Inherently Safer Design', 2nd ed.
• Wikipedia — Azeotrope (ethanol–water azeotrope: 95.63% ethanol / 4.37% water by mass, boiling 78.2 °C)
• Wikipedia — Azeotrope (ethanol–water azeotrope figures retrieved 2026)

Every Wunder lesson is built from real, reputable sources — never invented.

Related Science courses