When you boil water, you aren't changing the elements. You're just making water vapor. However, when you burn paper, it becomes carbon (mostly). So physical changes will not change the substance, only chemical changes will.
A lemon juice cleans a penny. I believe this to be the answer because the lemon cleans the penny but no molecules change
C.Work was required by an outside force.
<span>all of the above can be saturated molecules </span>