Chemistry: The science of the composition, structure, properties, and reactions of matter, especially of atomic and molecular systems.
Biology: The science of life and of living organisms, including their structure, function, growth, origin, evolution, and distribution. It includes botany and zoology and all their subdivisions.
Those are the dictionary definitions. Chemistry is much more involved in math and physics than biology is and chemistry is pretty cut and dry because you deal with chemicals. Biology gets messy because living things are messy - lots of fluids and moving parts.