the medicines we take, many of the clothes we wear and the foods we eat, even the oxygen we breathe..all
owe their existence to chemical reactions. during photosynthesis, carbon dioxide and water react, it the presence of lignt, to yield glucose (in which the chemical enegy is stored) and oxygen. the words you just heard accurately describe the photosynthetic process. but reactions can also be represented using the language of chemistry. notice the numbers in front of some of the substances. these coefficients are needed chemical reactions, matter, itself, is conserved. the law of conservation of matter (which states that mater is neither created nor destroyed during a chemical reaction), means that such reactions must be represented by balanced chemical equations. how and why are chemical equations balanced