Bible study is very important, but 2 Timothy 2:15 is not just a command to study the Bible. Being an approved workman involves much more.
It is very important that we think about what we sing in our worship to God if we want to be pleasing to Him.
The difference between leavened and unleavened bread is found in the word itself - leaven. Leaven is what is placed in bread dough to make the bread rise. It is placed in the dough and spreads throughout the entire lump.