Suppose you have this great recipe for chocolate ice cream. You like to make it at home for your family and friends. You make it in a little one-gallon machine that goes into your freezer. But what if you sell your recipe to a big food company? Now they have to be able to make thousands of gallons a day. Each gallon of ice cream needs to taste exactly the same and look exactly the same.
What kind of equipment could they use? How would the recipe change? How can the factory make the ice cream at low cost? These are all questions for the chemical engineer.