Chemistry is that the science involved elements and compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and therefore the changes they undergo during a reaction with other substances. Chemistry is that the study of matter, its properties, how and why substances combine or separate to make other substances, and the way substances interact with energy. Chemistry is one among the physical sciences that help us to explain and explain our world. within the scope of its subject, chemistry occupies an intermediate position between physics and biology. it's sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. for instance, chemistry explains aspects of plant chemistry (botany), the formation of igneous rocks (geology), how atmospheric ozone is made and the way environmental pollutants are degraded (ecology), the properties of the soil on the moon (astrophysics), how medications work (pharmacology), and the way to gather DNA evidence at a criminal offense scene (forensics).