Enabling the chemPad tool when you are writing a question is simple — you set $PAD='chem' in Answer. But creating effective chemPad questions also involves specifying how your students' responses should be parsed, in order to: • restrict or allow different kinds of chemically equivalent notation, for example, elements in a formula listed in non-standard order • accurately score correct and incorrect student responses • provide meaningful hints when your students enter incorrect responses To do this, you must set the $CHEM variable to specify one or more parsing methods as described in the following topics.