In a chemical reaction no "particles" are converted to energy.
But, the electrons in the reaction products if it is an exothermic
reaction (heat is given off) are less tightly bound than they were before.
Since mass and energy are equivalent, the reaction products will weigh
very slightly less than the starting material.
Dr. Mark H. Shapiro
Physics Department
California State University, Fullerton
P.O. Box 6866
Fullerton, California 92834-6866