Stoichiometry is a kind of calculation in chemistry. It’s sort of like bookkeeping. Stoichiometry lets you figure out how much of a substance is used up or produced in a chemical reaction. It’s really common to measure the amount of one reactant, in order to figure out how much product you expect to get. Or, given how much of one reactant you have, you might want to figure out how much of a second reactant to add so you don’t have any left over. This video introduces the concept of stoichiometry, and how balanced chemical equations can be used like recipes (for instance, the recipe for grilled cheese sandwiches). We give an example of how to solve mole-to-mole problems. Part II will cover mass-to-mass problems.