The Law of Conservation of Mass the principle that in any closed system subjected to no external forces, the mass is constant irrespective of its changes in form; the principle that matter cannot be created or destroyed. The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. For example, when wood burns, the mass of the soot, ashes, and gases, equals the original mass of the charcoal and the oxygen when it first reacted. So the mass of the product equals the mass of the reactant. https://courses.lumenlearning.com/introchem/chapter/the-law-of-conservation-of-mass/(helping link).

-Energy is the ability to do work, or cause change. It can be either kinetic energy or potential energy. Kinetic energy-Energy in MOTION. Potential energy-Energy that is stored. -Ad kenitic and potential energy, and you get MECHANICAL energy. Thermal Energy: Energy that can be felt as heat. The Sun is thermal energy. Electrical Energy: This is caused by electrons moving around and flowing through a path. Light Energy: This travels through space and many forms of it can be seen by people. Sound Energy: This is another form of energy that people can experience. Sometimes we can hear sound. It is what vibrates through matter.     Chemicals also have chemical energy that is stored and released when chemical bonds are broken.