Reactants, products and leftovers – sandwiches and molecules

Integrated ScienceChemical ReactionsAges 13–14

Use the sliders to set the number of ingredients (sandwiches) or reactant molecules (making water, making ammonia, burning methane), then see how much product forms and how much is left over, based on the fixed ratios of a recipe or a balanced equation. An atom count table shows that the total number of atoms of each element stays the same. A four-level Game screen practises finding the limiting and excess amounts, from easy to hard. Adapted from the "Reactants, Products and Leftovers" simulation by PhET Interactive Simulations, University of Colorado Boulder (CC BY 4.0); rewritten.

Lesson: Conservation of mass, chemical equations