To derive precise results, it is important for other variables in an experiment to be controlled. Accuracy and precision are the key factors of every practical experiment carried out.
During the course of experiments, special emphasis is laid on the objective of the experiment. Procedures and precautions are highly objective-oriented. There are possibilities of errors as the surrounding becomes an integral part of the system in practicals.
Certain physical and chemical quantities are ignored in theoretical assessment, but they affect the practical work. Impurities and uncontrolled reactions can be barriers. Optimum conditions are sought before conducting experiments.