By James McAbee
Physical changes are changes affecting the form of a chemical substance, but not its chemical composition.
Chemical changes occur when a substance combines with another to form a new substance, called synthesis or, alternatively, decomposes into two or more different substances
Precipitation is the formation of a solid in a solution or inside another solid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid solution, the solid formed is called the precipitate.
In thermodynamics, the term exothermic describes a process or reaction that releases energy from the system, usually in the form of heat, but also in a form of light, electricity, or sound
In thermodynamics, the term endothermic describes a process or reaction in which the system absorbs energy from its surroundings in the form of heat